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cannawizard
Well-Known Member
**nah, just saw the post, even if it did get all the way here.. i might be too faded to know.. lol ,.the real ATF cut might be.. im not sure if this one is the real deal..
cannawizard
Well-Known Member
cannawizard
Well-Known Member
**hhhmm.. just an obs3rvation, but under blue LEDs (c02 peaking at 3.5/4kppm ..veg) --i see no retarded growth.. just the opposite... hhmmm (wish i could see whats happening around the stomas)
--insomnia rant..
--insomnia rant..
Joedank
Well-Known Member
I have the tek I use for check ing stomata... If you want it but here is food for thought..http://www.geocraft.com/WVFossils/PageMill_Images/image354.gif
*
The CO2 Record in Plant Fossils
The Ice Core Record
The Presumption of CO2 Stability
Basis for the Estimate of Pre-Industrial CO2
The Last 15,000 Years-- Reconsidered
Putting Things in Perspective
The CO2 Record in Plant Fossils
Plant fossils obtained from sedimentary rocks and peat deposits are a relatively new tool being used to unravel Earth's carbon dioxide (CO2) history. Tiny pores on plant leaves and needles called stomata regulate carbon dioxide absorption and water vapor release. Stomata numbers decrease during times of high atmospheric CO2, and increase when atmospheric CO2 is low.
*
Nature's CO2 meter:
A standardized way of counting stomata-- called the stomatal index ( SI [%] )-- has been found to be a good way to estimate the CO2 content of the atmosphere when the plant was alive. The SI-CO2 relationship varies according to plant species, habitat altitude, and other factors.
Correlation charts are constructed using modern plant specimens by determining their SI numbers and corresponding CO2 concentrations. When SI and CO2 ranges are fully characterized for a plant species, the charts are used as to estimate CO2 levels for related species in the geologic past.
To determine plant age Carbon14 methods are usually used to about 40,000 years ago. For older material, other dating methods are used.
Image courtesy of: UC Berkeley; The story in the stomata
Because plant stomata numbers do not change after the leaves or needles fall from the parent plant, they make a good indicator or proxy of atmospheric CO2 in Earth's past. What they show is that the popular belief that CO2 levels prior to the Industrial Revolution were a steady 280 ppm (parts per million) may be incorrect.
As illustrated below, studies of stomata for recent and fossilized plants show that atmospheric CO2 levels over the last 15,000 years have been higher and much more variable than previously supposed. Much of what we think we know about CO2 levels of the past 800,000 years is based on the ice core record.
*
Recent stomata studies show that CO2 was more variable and the average CO2 concentrations have been significantly higher during our Holocene interglacial period (last 11,000 years) than are indicated by the ice core record.
Read below for more details.
*
The Ice Core Record
Ice cores obtained by drilling into permantent ice caps in Antarctica and Greenland have been the most important way to determine past levels of carbon dioxide-- however, recent stomata studies show that the ice core record may be misleading in several important respects.
For example, when ice cores are crushed to extract the gases from trapped air bubbles to determine CO2 content, there is an assumption made that ice bubbles preserve an accurate record of the Earths CO2 history. However, the chemical composition of ice bubbles undergo changes that may distort this record.
Accumulating ice layers can take a century or more to become buried deep enough to be isolated from the atmosphere, which at the South Pole occurs at a depth of approximately 120 m. The resulting heat and pressure causes gas exchange between ice layers, which modifies the chemistry of ice air bubbles. At burial depths of between 900 and 1200 meters the pressure is so great that air bubbles in ice disappear and the gases recombine with liquids and ice crystals. Such processes tend to smooth away variability in the ice record and may also make CO2 levels appear lower than they really were, obscuring much of the resolution pertaining to CO2 variability (1-4).
ice core photo by: Vin Morgan
Palaeo Environment (Ice Cores) Field Work
"Liquid water is common in polar snow and ice, even at temperatures as low as -72C, (and) in cold water, CO2 is 70 times more soluble than nitrogen and 30 times more soluble than oxygen-- guaranteeing that the proportions of the various gases that remain in the trapped, ancient air will change. Moreover, under the extreme pressure that deep ice is subjected to -- 320 bars, or more than 300 times normal atmospheric pressure -- high levels of CO2 get squeezed out of ancient air."
Zbigniew Jaworowski (
expert in the atmospheric deposition of radioactive contaminants in glacial ice
Figure 1. (ref. 22)
Figure 2. (ref. 22)
Although the ice core record represents a very nice overall view of temperature and CO2 trends over many thousands of years, their reliability for resolving details over timescales of decades-- or in some cases several centuries-- is limited. Nonethess, these data are used as the principle evidence to show that CO2 levels in excess of 300 parts per million are unprecedented in all of human history and a cause for concern.
*
The Presumption of CO2 Stability
The records of CO2 and Temperature over the last 15,000 years (but without the stomata CO2 record) appear in Figure 3. Except for the South Pole Air Flask CO2 measurements, all other data shown (including temperature) are from ice cores.
Figure 3. The CO2 record for the past 15,000 is comprised of ice cores, mostly. These came from Law Dome and Dome C in Antarctica. Since 1957 the CO2 record at the South Pole has been by analyzing Air Flask samples. (see larger image). By convention, "Years B.P." (Before Present) begins 1950 AD, which is why later years are "negative."
.
According to the Dome C and Law Dome ice cores, for nearly 15,000 years prior to the Industrial Revolution CO2 has remained below 280 ppm (parts per million), while only the youngest part of the Law Dome cores (after 1900 AD) show CO2 concentrations higher than 300 ppm.
The youngest CO2 data, is not based on ice cores but on South Pole Air Flask samples-- which consistently show CO2 higher than 300 ppm. The point in time useful for considering what CO2 concetrations really were before humans started to burn fossil fuels is at the start of the Industrial Revolution-- about 1750 AD. A key assumption is that pre-Industrial CO2 concentrations were less than 280 ppm and that everything above that is caused by humans. This assumption, however, is not without problems, although seldom discussed.
*
Basis for the Estimate of Pre-Industrial CO2
The Industrial Revolution started in Europe in the mid 1700's. The time before is referred to as "Pre-Industrial" time.
Because reliable CO2 air tests were not being performed until the 1800's, the presumed CO2 concentration in 1750 is 280 ppm, based largely on ice core data and early work by G.S. Callendar.
In the 1800's direct air CO2 measurements were performed by various researchers. Interestingly, the CO2 levels reported by them were mostly in excess of 300 ppm. For reasons that are unclear, only a few of these tests were considered valid by G.S. Calendar (1898-1964)-- the grandfather of the theory of man-made global warming. Today, the remaining data are largely ignored, although a few commentators like E. Beck and Z. Jaworoski suggest the data--some compiled by Nobel Prize laureates-- are generally valid and were inappropriately dismissed (4, 21) .
Callendar claimed humans had increased CO2 concentrations in the atmosphere by burning fossil fuels, and had thereby changed the atmosphere from 274 ppmv to 325 ppmv by 1935-- resulting in a 18.3 percent increase which had caused the global surface temperature to rise 0.33 deg. C (5). However, CO2 data available at the time showed concentrations ranged between 250 ppm and 550 ppm (Figure 4). Callendar has been accused of cherry-picking data from a sampling of 19th century averages, using 26 that supported his ideas, but rejecting 16 that were higher than his assumed low global average, and 2 that were lower (6).
Despite numerous 19th century air measurements showing +300 ppm CO2 levels, and despite the fact that many of the youngest ice cores showed higher than expected CO2 values and so were shifted forward 90-100 years from previously-established dates so that they would match the more elevated CO2 levels of 20th century air samples, the ice core record is today generally used to represent pre-1957 CO2 concentrations. The Intergovernmental Panel on Climate Change (IPCC) places the pre-industrial concentration of CO2 in the atmosphere at 280 ppm, based largely on the ice core record, although this has never been otherwise substantiated (7).
When systematic air readings began in 1957 AD, CO2 air values were about 315 ppm. Today, CO2 concentrations are about 384 ppm. Current estimates of the anthropogenic (man-made) component of atmospheric CO2 range between 4% (9) and 25% (the latter assumes Pre-Industrial levels were 280 ppm, and assumes everything over that today is man-made). The problem with the 280 ppm baseline figure is that increasing evidence suggests this figure may be too low.
CO2 levels exceeding 300 ppm, we are told, are unnatural and unprecedented, but available 19th century CO2 air data and studies of plant stomata suggest another side to the story.
*Fiction:
*"The recent rate of change is dramatic and unprecedented; increases in CO2 never exceeded 30 ppm in 1 kyr yet now CO2 has risen by 30 ppm in just the last 17 years. "
Intergovernmental Panel on Climate Change (IPCC)
Working Group I: The Physical Science Basis of Climate Change
4th Assessment Report, 2007
*Fiction:
*"At no point in the last 650,000 years before the pre-industrial era did the CO2 concentrations go above 300 part per million..."
from, An Inconvenient Truth
by, former Vice President Al Gore
(now, chairman and co-founder of Generation Investment Management--
a London-based business that sells carbon credits)
*Fact:
**"The majority of the stomatal frequency-based estimates of CO2 for the Holocene do not support the widely accepted concept of comparably stable CO2 concentrations throughout the past 11,500 years."
F. Wagner, et.al., 2004
Paleoecologist and stomata research scientist (13)
*
The Last 15,000 Years-- Reconsidered
Studies of plant stomata show that the currently-held view of predominantly stable CO2 levels (260-280 ppm) before the Industrial Revolution (1750 AD, i.e. 200 years B.P.) may be an inaccurate view. CO2 levels appear to have regularly exceeded 280 ppm-- the average of CO2 concentrations across the Holocene interglacial period (last 11,000 years) appears to have been approximately 305 ppm (see ref. 10-20).
Contrary to the prevailing notion of CO2 stability, CO2 swings of 20-50 ppm or more over timespans of 500-1000 years appear to be the norm-- not the exception.
Figure 5. Illustrated here are results from recent stomata studies which show that CO2 was more variable and the average CO2 concentrations have been significantly higher during our Holocene interglacial period (last 11,000 years) than are indicated by the ice core record. A precipitous drop in CO2 during the "Younger Dryas" was captured nicely by the stomata record, but missed by the CO2 record in ice cores. (larger image).
*
Stomata researchers regard the plant stomata proxy as a reliable means to measure CO2 levels in the geologic past, including the Holocene interglacial period, which spans the period from about 12,000 years ago and continues to the present.
"Stomatal data increasingly substantiate a much more dynamic Holocene CO2 evolution than suggested by ice core data "
L. Kouwenberg, et.al. 2005 (9)
Laboratory of Palaeobotany and Palynology, Utrecht University, Netherlands
Data from various stomata studies (ref. 10-20) show CO2 concentrations over the last 11,000 years varied between 260 and 340 ppm (average: 305 ppm). In contrast, the Dome C ice core record shows no significant variability and considerably lower overall CO2 levels (average: 270 ppm).
A sharp CO2 decline is indicated between 11,500 to 12,800 B.P., coinciding with an abrupt cooling phase, known as the "Younger Dryas" (Figure 5 ). While this event is obscured in the Antarctic Dome C ice core CO2 record, it shows up clearly in the stomata CO2 record.
Based on these stomata data, the conventional Pre-Industrial baseline of 280 ppm may be understated by about 25 ppm. In other words, 24% of the presumed 105 ppm Industrial Era CO2 increase may in fact be a result of bias and poor resolution of CO2 variability in the ice cores.
While the stomata data show higher values of CO2 than do pre-1900 ice data, they generally agree with the very youngest part of the Law Dome ice data (1900-1957 AD) and also with the contemporary S. Pole Air Flask CO2 record (actual air samples) begun in 1957 and continuing today. In other words, stomata results agree with the data that are least susceptible to distortion and diffusion errors.
The stomata record offers important evidence to challenge the notion that variations in CO2 levels of 20-50 ppm over timespans of less than 1000-years are "unprecedented" or that Pre-Industrial CO2 concentrations never went above 300 ppm-- both may, in fact, have been normal.
*
Putting Things in Perspective
New studies of plant stomata add important information about natural CO2 variations in Earth's atmosphere. Such studies show that natural variations in CO2 are more dramatic than we have been led to believe, and that CO2 levels which regularly rise past 300 ppm may be the norm-- not the exception-- during the last 11,000 years. Natural CO2 levels up to 340 ppm are suggested during this time, challenging claims that 300 ppm represents a CO2 threshold which is both "unprecedented" and un-natural in our recent climate history.
In reality, the actual amount of human additions to CO2 over the past 250 years is more of an academic issue than a practical one, as the theory that human additions to atmospheric CO2 are the principle driver of Earth's temperature changes, has not been proven. For example:
The notion that CO2 drives temperature is disproved by the ice core record,which shows that temperatures rise first, then CO2 follows later.
While CO2 has risen steadily over the last decade, global surface temperatures have not increased.
Temperatures in the mid troposphere (5 km up), where signals of greenhouse warming should be strongest, have actually declined since 2000. According to greenhouse theory, this should not be happening if CO2 increases are the primary cause of global warming.
As the case for a CO2 problem looks increasingly uncertain it is appropriate to question climate projections and computer models on global warming to ensure that we are not basing important and expensive decisions on information that currently may be no more meaningful than answers given by a magic 8-ball.
Given the many complexities of clouds, ocean sinks, cosmic influences, and historical uncertainties, it is clear that our understanding of CO2 levels and climate cycles is incomplete. A new piece to this puzzle comes from simple plant fossils, which hold important clues about Earth's dynamic climate past-- and future.
Return to Carboniferous Climate
*Articles || Other || What's New || Table of Contents
Created: January 24, 2010
References:
1) Digging for Ancient Air at South Pole; Todd Sowers, In Depth (newsletter of the National Ice Core Laboratory), vol. 4, issue 1, Spring 2009.
2) CO2 diffusion in polar ice: observations from naturally formed CO2 spikes in the Siple Dome (Antarctica) ice core; Jinho Ahn, Melissa Headly, Martin Wahlen, Edward J. Brook, Paul A. Mayewski, Kendrick C. Taylor; Journal of Glaciology, Vol. 54, No. 187, 2008.
3) Everyone is entitled to their own opinion but not their own facts; Tom Quirk, A presentation to The Lavoisier Group Workshop: Rehabilitating Carbon Dioxide, held in Melbourne, Australia, June 29-30, 2007)
4) Another Global Warming Fraud Exposed: Ice Core Data Show No Carbon Dioxide Increase; Zbigniew Jaworowski, Ph.D., 21st Century, pp 42-52, Spring 1997.
5) Ibid.
6) Ibid.
7) Ibid.
The ice-core man "Once upon a time, and for millennia before then, carbon dioxide levels in the atmosphere were low and stable..."; by Lawrence Solomon for National Post, May 23, 2007; re-printed by canada.com.
9) The distribution of CO2 between atmosphere, hydrosphere, and lithosphere; minimal influence from anthropogenic CO2 on the global "Greenhouse Effect"; Tom V. Segalstad; Mineralogical-Geological Museum, University of Oslo, Norway
10) Atmospheric CO2 fluctuations during the last millennium reconstructed by stomatal frequency analysis of Tsuga heterophylla needles; Lenny Kouwenberg, Rike Wagner, Wolfram Kurschner, Henk Visscher; Geology, January 2005.
11) The Preboreal climate reversal and a subsequent solar-force climate shift; J. van der Plicht, B. van Geel, S.J.P. Bohnche, J.A.A. Box, M. Blaauw, A.O.M. Speranza, R. Muscheler, and S. Bjorck; Journal of Quaternary Science (2004) 19(3), pp. 263-269.
12) Rapid atmospheric CO2 changes associated with the 8,200-years-B.P. cooling event; Friederike Wagner, Bent Aaby, and Henk Visscher; PNAS, September 17, 2002; vol. 99, no.19, pp. 12011-12014.
13) Reproducibility of Holocene atmosphere CO2 records based on stomatal frequency; Friederike Wagner, Lenny L.R. Kouwenberg, Thomas B. van Hoof, Henk Visscher; Quaternary Science Reviews 23 (2004), pp.1947-1954.
14) Stomatal evidence for a decline in atmospheric CO2 concentrtion during the Younger Dryas stadial: a comparison with Antarctic ice core records; J.C. McElwain, F.E. Mayle, and D.J. Beerling; Journal of Quaternary Science (2002), 17(1), pp. 21-29.
15) Early Holocene Atmospheric CO2 Concentrations; Technical Comments; Science, vol. 286, December 3, 1999
16) Stomatal-based inference models for reconstruction of atmospheric CO2 concentration: a method assessment using a calibration and validation approach; W. Finsinger and F. Wagner-Cremer; The Holocene, 19,5 (2009), pp. 757-764.
17) Last interglacial atmospheric CO2 changes from stomatal index data and their relation to climatic variations; Mats Rundgren, Svante Bjorck, Dan Hammarlund; Global and Planetary Change 49 (2005), pp. 47-62.
1 Stomatal frequency adjustment of four conifer species to historical changes to atmospheric CO2; Lenny L. R. Kouwenberg, Jennifer C. McElwain, Wolfram M. Kürschner, Friederike Wagner, David J. Beerling, Francis E. Mayle and Henk Visscher; American Journal of Botany. 2003; 90: pp.610-619.
19) CO2 radiative forcing during the HoloceneThermal Maximum revealed by stomatal frequency of Iberian oak leaves; I. Garc´ýa-Amorena, F. Wagner-Cremer, F. Gomez Manzaneque, T. B. van Hoof, S. Garc´ýa A´ lvarez, and H. Visscher; Biogeosciences Discuss., 5, 39453964, 2008.
20) Abrupt climatic changes and an unstable transition into a late Holocene Thermal Decline: a multiproxy lacustrine record from southern Sweden; Catherine A. Jessen, Mats Rundgren, Svane Bjorck, and Dan Hammarlund; Journal of Quaternary Science (2005), 20(4), pp. 349-362.
21) 180 Years of Atmospheric CO2 Gas Analysis by Chemical Methods; Ernst-Georg Beck; Reprinted from Energy & Environment, vol 18, no. 2, 2007.
*
22) The Ice Core Record:
Graphs of Temperature (Figure 1) and Carbon Dioxide (Figure 2) were created using Micosoft Excel and published data from the following sources.
Carbon Dioxide
South Pole Air Flask (1957-2006 AD)
Atmospheric CO2 concentrations (ppmv) derived from flask samples collected at South Pole, Antarctica
L.P. Steele, P.B. Krummel, R.L. Langenfelds
Atmospheric, Research, Commonwealth, Scientific, and Industrial Research Organization, Australia
August 2007
Law Dome ice core (1006-1954 AD)
Historical CO2 record from the Law Dome DE08, DE08-2, and DSS ice cores
D.M. Eheridge
L.P. Steele
R.K. Langenfelds
R.J. Francey
Division of Atmospheric Research, CSIRO, Aspendael, Victoria, Australia
J.M. Barnola
Laboratoire of Glaciologie et Geophysique de l'Environnement, Saint Martin d'Heres-Cedex, France
V.I Morgan
Antarctic CRC and Australian Division, Hobart, Tasmania, Australia
Dome C ice core (1000-22,015 years B.P.)
Monnin, et.al., (2001)
University of Bern
*
Temperature
Radiosonde- Troposphere and L. Stratosphere (1979-2008 AD)
Surface-100 mb dataset (Global)
J.K Angell
Air Resources Laboratory
National Oceanographic and Atmospheric Administration (NOAA), 2009
S. Hemisphere Ground (1871-1978 AD)
S.HEMI Land-Ocean Temperature Index in 0.01 degrees Celsius base period: 1951-1980
sources: GHCN 1880-12/2009 + SST: 1880-11/1981 HadISST1 12/1981-12/2009 Reynolds v2 using elimination of outliers and homogeneity adjustment
Notes: 1950 DJF = Dec 1949 - Feb 1950
Vostok Ice Core (1812 AD -422,766 years B.P.)
Historical Isotopic Temperature Record from the Vostok Ice Core
The data available from CDIAC represent a major effort by researchers from France, Russia, and the U.S.A. Jouzel, J., C. Lorius, J.R. Petit, C. Genthon, N.I. Barkov,
V.M. Kotlyakov, and V.M. Petrov. 1987. Vostok ice core: a continuous sotope temperature record over the last climatic cycle (160,000 years). Nature 329:403-8.
Jouzel, J., N.I. Barkov, J.M. Barnola, M. Bender, J. Chappellaz,C. Genthon, V.M. Kotlyakov, V. Lipenkov, C. Lorius, J.R. Petit,D. Raynaud, G. Raisbeck, C. Ritz, T. Sowers, M. Stievenard, F. Yiou, and P. Yiou. 1993.
Extending the Vostok ice-core record of palaeoclimate to the penultimate glacial period. Nature 364:407-12
Jouzel, J., C. Waelbroeck, B. Malaize, M. Bender, J.R. Petit, M. Stievenard, N.I. Barkov, J.M. Barnola, T. King, V.M. Kotlyakov,V. Lipenkov, C. Lorius, D. Raynaud, C. Ritz, and T. Sowers. 1996.
Climatic interpretation of the recently extended Vostok ice records.
Climate Dynamics 12:513-521.
Petit, J.R., J. Jouzel, D. Raynaud, N.I. Barkov, J.-M. Barnola, I. Basile, M. Bender, J. Chappellaz, M. Davis, G. Delayque, M. Delmotte, V.M. Kotlyakov, M. Legrand, V.Y. Lipenkov, C. Lorius, L. Pepin, C. Ritz, E. Saltzman, and M. Stievenard. 1999.
Climate and atmospheric history of the past 420,000 years from the Vostok ice core, Antarctica. Nature 399: 429-436.
Source: J. R. Petit, D. Raynaud, C. Lorius
Laboratoire de Glaciologie et de Geophysique de l'Environnement
38402 Saint Martin d'Heres Cedex, France
J. Jouzel, G. Delaygue
Laboratoire des Sciences du Climat et de l'Environment
(UMR CEA/CNRS 1572)
91191 Gif-sur-Yvette Cedex, France
N. I. Barkov
Arctic and Antarctic Research Institute
Beringa Street 38
St. Petersburg 199397, Russia
V. M. Kotlyakov
Institute of Geography
Staromonetny, per 29, Moscow 109017, Russia
January 2000
*
The CO2 Record in Plant Fossils
The Ice Core Record
The Presumption of CO2 Stability
Basis for the Estimate of Pre-Industrial CO2
The Last 15,000 Years-- Reconsidered
Putting Things in Perspective
The CO2 Record in Plant Fossils
Plant fossils obtained from sedimentary rocks and peat deposits are a relatively new tool being used to unravel Earth's carbon dioxide (CO2) history. Tiny pores on plant leaves and needles called stomata regulate carbon dioxide absorption and water vapor release. Stomata numbers decrease during times of high atmospheric CO2, and increase when atmospheric CO2 is low.
*
Nature's CO2 meter:
A standardized way of counting stomata-- called the stomatal index ( SI [%] )-- has been found to be a good way to estimate the CO2 content of the atmosphere when the plant was alive. The SI-CO2 relationship varies according to plant species, habitat altitude, and other factors.
Correlation charts are constructed using modern plant specimens by determining their SI numbers and corresponding CO2 concentrations. When SI and CO2 ranges are fully characterized for a plant species, the charts are used as to estimate CO2 levels for related species in the geologic past.
To determine plant age Carbon14 methods are usually used to about 40,000 years ago. For older material, other dating methods are used.
Image courtesy of: UC Berkeley; The story in the stomata
Because plant stomata numbers do not change after the leaves or needles fall from the parent plant, they make a good indicator or proxy of atmospheric CO2 in Earth's past. What they show is that the popular belief that CO2 levels prior to the Industrial Revolution were a steady 280 ppm (parts per million) may be incorrect.
As illustrated below, studies of stomata for recent and fossilized plants show that atmospheric CO2 levels over the last 15,000 years have been higher and much more variable than previously supposed. Much of what we think we know about CO2 levels of the past 800,000 years is based on the ice core record.
*
Recent stomata studies show that CO2 was more variable and the average CO2 concentrations have been significantly higher during our Holocene interglacial period (last 11,000 years) than are indicated by the ice core record.
Read below for more details.
*
The Ice Core Record
Ice cores obtained by drilling into permantent ice caps in Antarctica and Greenland have been the most important way to determine past levels of carbon dioxide-- however, recent stomata studies show that the ice core record may be misleading in several important respects.
For example, when ice cores are crushed to extract the gases from trapped air bubbles to determine CO2 content, there is an assumption made that ice bubbles preserve an accurate record of the Earths CO2 history. However, the chemical composition of ice bubbles undergo changes that may distort this record.
Accumulating ice layers can take a century or more to become buried deep enough to be isolated from the atmosphere, which at the South Pole occurs at a depth of approximately 120 m. The resulting heat and pressure causes gas exchange between ice layers, which modifies the chemistry of ice air bubbles. At burial depths of between 900 and 1200 meters the pressure is so great that air bubbles in ice disappear and the gases recombine with liquids and ice crystals. Such processes tend to smooth away variability in the ice record and may also make CO2 levels appear lower than they really were, obscuring much of the resolution pertaining to CO2 variability (1-4).
ice core photo by: Vin Morgan
Palaeo Environment (Ice Cores) Field Work
"Liquid water is common in polar snow and ice, even at temperatures as low as -72C, (and) in cold water, CO2 is 70 times more soluble than nitrogen and 30 times more soluble than oxygen-- guaranteeing that the proportions of the various gases that remain in the trapped, ancient air will change. Moreover, under the extreme pressure that deep ice is subjected to -- 320 bars, or more than 300 times normal atmospheric pressure -- high levels of CO2 get squeezed out of ancient air."
Zbigniew Jaworowski (
expert in the atmospheric deposition of radioactive contaminants in glacial ice
Figure 1. (ref. 22)
Figure 2. (ref. 22)
Although the ice core record represents a very nice overall view of temperature and CO2 trends over many thousands of years, their reliability for resolving details over timescales of decades-- or in some cases several centuries-- is limited. Nonethess, these data are used as the principle evidence to show that CO2 levels in excess of 300 parts per million are unprecedented in all of human history and a cause for concern.
*
The Presumption of CO2 Stability
The records of CO2 and Temperature over the last 15,000 years (but without the stomata CO2 record) appear in Figure 3. Except for the South Pole Air Flask CO2 measurements, all other data shown (including temperature) are from ice cores.
Figure 3. The CO2 record for the past 15,000 is comprised of ice cores, mostly. These came from Law Dome and Dome C in Antarctica. Since 1957 the CO2 record at the South Pole has been by analyzing Air Flask samples. (see larger image). By convention, "Years B.P." (Before Present) begins 1950 AD, which is why later years are "negative."
.
According to the Dome C and Law Dome ice cores, for nearly 15,000 years prior to the Industrial Revolution CO2 has remained below 280 ppm (parts per million), while only the youngest part of the Law Dome cores (after 1900 AD) show CO2 concentrations higher than 300 ppm.
The youngest CO2 data, is not based on ice cores but on South Pole Air Flask samples-- which consistently show CO2 higher than 300 ppm. The point in time useful for considering what CO2 concetrations really were before humans started to burn fossil fuels is at the start of the Industrial Revolution-- about 1750 AD. A key assumption is that pre-Industrial CO2 concentrations were less than 280 ppm and that everything above that is caused by humans. This assumption, however, is not without problems, although seldom discussed.
*
Basis for the Estimate of Pre-Industrial CO2
The Industrial Revolution started in Europe in the mid 1700's. The time before is referred to as "Pre-Industrial" time.
Because reliable CO2 air tests were not being performed until the 1800's, the presumed CO2 concentration in 1750 is 280 ppm, based largely on ice core data and early work by G.S. Callendar.
In the 1800's direct air CO2 measurements were performed by various researchers. Interestingly, the CO2 levels reported by them were mostly in excess of 300 ppm. For reasons that are unclear, only a few of these tests were considered valid by G.S. Calendar (1898-1964)-- the grandfather of the theory of man-made global warming. Today, the remaining data are largely ignored, although a few commentators like E. Beck and Z. Jaworoski suggest the data--some compiled by Nobel Prize laureates-- are generally valid and were inappropriately dismissed (4, 21) .
Callendar claimed humans had increased CO2 concentrations in the atmosphere by burning fossil fuels, and had thereby changed the atmosphere from 274 ppmv to 325 ppmv by 1935-- resulting in a 18.3 percent increase which had caused the global surface temperature to rise 0.33 deg. C (5). However, CO2 data available at the time showed concentrations ranged between 250 ppm and 550 ppm (Figure 4). Callendar has been accused of cherry-picking data from a sampling of 19th century averages, using 26 that supported his ideas, but rejecting 16 that were higher than his assumed low global average, and 2 that were lower (6).
Despite numerous 19th century air measurements showing +300 ppm CO2 levels, and despite the fact that many of the youngest ice cores showed higher than expected CO2 values and so were shifted forward 90-100 years from previously-established dates so that they would match the more elevated CO2 levels of 20th century air samples, the ice core record is today generally used to represent pre-1957 CO2 concentrations. The Intergovernmental Panel on Climate Change (IPCC) places the pre-industrial concentration of CO2 in the atmosphere at 280 ppm, based largely on the ice core record, although this has never been otherwise substantiated (7).
When systematic air readings began in 1957 AD, CO2 air values were about 315 ppm. Today, CO2 concentrations are about 384 ppm. Current estimates of the anthropogenic (man-made) component of atmospheric CO2 range between 4% (9) and 25% (the latter assumes Pre-Industrial levels were 280 ppm, and assumes everything over that today is man-made). The problem with the 280 ppm baseline figure is that increasing evidence suggests this figure may be too low.
CO2 levels exceeding 300 ppm, we are told, are unnatural and unprecedented, but available 19th century CO2 air data and studies of plant stomata suggest another side to the story.
*Fiction:
*"The recent rate of change is dramatic and unprecedented; increases in CO2 never exceeded 30 ppm in 1 kyr yet now CO2 has risen by 30 ppm in just the last 17 years. "
Intergovernmental Panel on Climate Change (IPCC)
Working Group I: The Physical Science Basis of Climate Change
4th Assessment Report, 2007
*Fiction:
*"At no point in the last 650,000 years before the pre-industrial era did the CO2 concentrations go above 300 part per million..."
from, An Inconvenient Truth
by, former Vice President Al Gore
(now, chairman and co-founder of Generation Investment Management--
a London-based business that sells carbon credits)
*Fact:
**"The majority of the stomatal frequency-based estimates of CO2 for the Holocene do not support the widely accepted concept of comparably stable CO2 concentrations throughout the past 11,500 years."
F. Wagner, et.al., 2004
Paleoecologist and stomata research scientist (13)
*
The Last 15,000 Years-- Reconsidered
Studies of plant stomata show that the currently-held view of predominantly stable CO2 levels (260-280 ppm) before the Industrial Revolution (1750 AD, i.e. 200 years B.P.) may be an inaccurate view. CO2 levels appear to have regularly exceeded 280 ppm-- the average of CO2 concentrations across the Holocene interglacial period (last 11,000 years) appears to have been approximately 305 ppm (see ref. 10-20).
Contrary to the prevailing notion of CO2 stability, CO2 swings of 20-50 ppm or more over timespans of 500-1000 years appear to be the norm-- not the exception.
Figure 5. Illustrated here are results from recent stomata studies which show that CO2 was more variable and the average CO2 concentrations have been significantly higher during our Holocene interglacial period (last 11,000 years) than are indicated by the ice core record. A precipitous drop in CO2 during the "Younger Dryas" was captured nicely by the stomata record, but missed by the CO2 record in ice cores. (larger image).
*
Stomata researchers regard the plant stomata proxy as a reliable means to measure CO2 levels in the geologic past, including the Holocene interglacial period, which spans the period from about 12,000 years ago and continues to the present.
"Stomatal data increasingly substantiate a much more dynamic Holocene CO2 evolution than suggested by ice core data "
L. Kouwenberg, et.al. 2005 (9)
Laboratory of Palaeobotany and Palynology, Utrecht University, Netherlands
Data from various stomata studies (ref. 10-20) show CO2 concentrations over the last 11,000 years varied between 260 and 340 ppm (average: 305 ppm). In contrast, the Dome C ice core record shows no significant variability and considerably lower overall CO2 levels (average: 270 ppm).
A sharp CO2 decline is indicated between 11,500 to 12,800 B.P., coinciding with an abrupt cooling phase, known as the "Younger Dryas" (Figure 5 ). While this event is obscured in the Antarctic Dome C ice core CO2 record, it shows up clearly in the stomata CO2 record.
Based on these stomata data, the conventional Pre-Industrial baseline of 280 ppm may be understated by about 25 ppm. In other words, 24% of the presumed 105 ppm Industrial Era CO2 increase may in fact be a result of bias and poor resolution of CO2 variability in the ice cores.
While the stomata data show higher values of CO2 than do pre-1900 ice data, they generally agree with the very youngest part of the Law Dome ice data (1900-1957 AD) and also with the contemporary S. Pole Air Flask CO2 record (actual air samples) begun in 1957 and continuing today. In other words, stomata results agree with the data that are least susceptible to distortion and diffusion errors.
The stomata record offers important evidence to challenge the notion that variations in CO2 levels of 20-50 ppm over timespans of less than 1000-years are "unprecedented" or that Pre-Industrial CO2 concentrations never went above 300 ppm-- both may, in fact, have been normal.
*
Putting Things in Perspective
New studies of plant stomata add important information about natural CO2 variations in Earth's atmosphere. Such studies show that natural variations in CO2 are more dramatic than we have been led to believe, and that CO2 levels which regularly rise past 300 ppm may be the norm-- not the exception-- during the last 11,000 years. Natural CO2 levels up to 340 ppm are suggested during this time, challenging claims that 300 ppm represents a CO2 threshold which is both "unprecedented" and un-natural in our recent climate history.
In reality, the actual amount of human additions to CO2 over the past 250 years is more of an academic issue than a practical one, as the theory that human additions to atmospheric CO2 are the principle driver of Earth's temperature changes, has not been proven. For example:
The notion that CO2 drives temperature is disproved by the ice core record,which shows that temperatures rise first, then CO2 follows later.
While CO2 has risen steadily over the last decade, global surface temperatures have not increased.
Temperatures in the mid troposphere (5 km up), where signals of greenhouse warming should be strongest, have actually declined since 2000. According to greenhouse theory, this should not be happening if CO2 increases are the primary cause of global warming.
As the case for a CO2 problem looks increasingly uncertain it is appropriate to question climate projections and computer models on global warming to ensure that we are not basing important and expensive decisions on information that currently may be no more meaningful than answers given by a magic 8-ball.
Given the many complexities of clouds, ocean sinks, cosmic influences, and historical uncertainties, it is clear that our understanding of CO2 levels and climate cycles is incomplete. A new piece to this puzzle comes from simple plant fossils, which hold important clues about Earth's dynamic climate past-- and future.
Return to Carboniferous Climate
*Articles || Other || What's New || Table of Contents
Created: January 24, 2010
References:
1) Digging for Ancient Air at South Pole; Todd Sowers, In Depth (newsletter of the National Ice Core Laboratory), vol. 4, issue 1, Spring 2009.
2) CO2 diffusion in polar ice: observations from naturally formed CO2 spikes in the Siple Dome (Antarctica) ice core; Jinho Ahn, Melissa Headly, Martin Wahlen, Edward J. Brook, Paul A. Mayewski, Kendrick C. Taylor; Journal of Glaciology, Vol. 54, No. 187, 2008.
3) Everyone is entitled to their own opinion but not their own facts; Tom Quirk, A presentation to The Lavoisier Group Workshop: Rehabilitating Carbon Dioxide, held in Melbourne, Australia, June 29-30, 2007)
4) Another Global Warming Fraud Exposed: Ice Core Data Show No Carbon Dioxide Increase; Zbigniew Jaworowski, Ph.D., 21st Century, pp 42-52, Spring 1997.
5) Ibid.
6) Ibid.
7) Ibid.
The ice-core man "Once upon a time, and for millennia before then, carbon dioxide levels in the atmosphere were low and stable..."; by Lawrence Solomon for National Post, May 23, 2007; re-printed by canada.com.9) The distribution of CO2 between atmosphere, hydrosphere, and lithosphere; minimal influence from anthropogenic CO2 on the global "Greenhouse Effect"; Tom V. Segalstad; Mineralogical-Geological Museum, University of Oslo, Norway
10) Atmospheric CO2 fluctuations during the last millennium reconstructed by stomatal frequency analysis of Tsuga heterophylla needles; Lenny Kouwenberg, Rike Wagner, Wolfram Kurschner, Henk Visscher; Geology, January 2005.
11) The Preboreal climate reversal and a subsequent solar-force climate shift; J. van der Plicht, B. van Geel, S.J.P. Bohnche, J.A.A. Box, M. Blaauw, A.O.M. Speranza, R. Muscheler, and S. Bjorck; Journal of Quaternary Science (2004) 19(3), pp. 263-269.
12) Rapid atmospheric CO2 changes associated with the 8,200-years-B.P. cooling event; Friederike Wagner, Bent Aaby, and Henk Visscher; PNAS, September 17, 2002; vol. 99, no.19, pp. 12011-12014.
13) Reproducibility of Holocene atmosphere CO2 records based on stomatal frequency; Friederike Wagner, Lenny L.R. Kouwenberg, Thomas B. van Hoof, Henk Visscher; Quaternary Science Reviews 23 (2004), pp.1947-1954.
14) Stomatal evidence for a decline in atmospheric CO2 concentrtion during the Younger Dryas stadial: a comparison with Antarctic ice core records; J.C. McElwain, F.E. Mayle, and D.J. Beerling; Journal of Quaternary Science (2002), 17(1), pp. 21-29.
15) Early Holocene Atmospheric CO2 Concentrations; Technical Comments; Science, vol. 286, December 3, 1999
16) Stomatal-based inference models for reconstruction of atmospheric CO2 concentration: a method assessment using a calibration and validation approach; W. Finsinger and F. Wagner-Cremer; The Holocene, 19,5 (2009), pp. 757-764.
17) Last interglacial atmospheric CO2 changes from stomatal index data and their relation to climatic variations; Mats Rundgren, Svante Bjorck, Dan Hammarlund; Global and Planetary Change 49 (2005), pp. 47-62.
1
Stomatal frequency adjustment of four conifer species to historical changes to atmospheric CO2; Lenny L. R. Kouwenberg, Jennifer C. McElwain, Wolfram M. Kürschner, Friederike Wagner, David J. Beerling, Francis E. Mayle and Henk Visscher; American Journal of Botany. 2003; 90: pp.610-619.19) CO2 radiative forcing during the HoloceneThermal Maximum revealed by stomatal frequency of Iberian oak leaves; I. Garc´ýa-Amorena, F. Wagner-Cremer, F. Gomez Manzaneque, T. B. van Hoof, S. Garc´ýa A´ lvarez, and H. Visscher; Biogeosciences Discuss., 5, 39453964, 2008.
20) Abrupt climatic changes and an unstable transition into a late Holocene Thermal Decline: a multiproxy lacustrine record from southern Sweden; Catherine A. Jessen, Mats Rundgren, Svane Bjorck, and Dan Hammarlund; Journal of Quaternary Science (2005), 20(4), pp. 349-362.
21) 180 Years of Atmospheric CO2 Gas Analysis by Chemical Methods; Ernst-Georg Beck; Reprinted from Energy & Environment, vol 18, no. 2, 2007.
*
22) The Ice Core Record:
Graphs of Temperature (Figure 1) and Carbon Dioxide (Figure 2) were created using Micosoft Excel and published data from the following sources.
Carbon Dioxide
South Pole Air Flask (1957-2006 AD)
Atmospheric CO2 concentrations (ppmv) derived from flask samples collected at South Pole, Antarctica
L.P. Steele, P.B. Krummel, R.L. Langenfelds
Atmospheric, Research, Commonwealth, Scientific, and Industrial Research Organization, Australia
August 2007
Law Dome ice core (1006-1954 AD)
Historical CO2 record from the Law Dome DE08, DE08-2, and DSS ice cores
D.M. Eheridge
L.P. Steele
R.K. Langenfelds
R.J. Francey
Division of Atmospheric Research, CSIRO, Aspendael, Victoria, Australia
J.M. Barnola
Laboratoire of Glaciologie et Geophysique de l'Environnement, Saint Martin d'Heres-Cedex, France
V.I Morgan
Antarctic CRC and Australian Division, Hobart, Tasmania, Australia
Dome C ice core (1000-22,015 years B.P.)
Monnin, et.al., (2001)
University of Bern
*
Temperature
Radiosonde- Troposphere and L. Stratosphere (1979-2008 AD)
Surface-100 mb dataset (Global)
J.K Angell
Air Resources Laboratory
National Oceanographic and Atmospheric Administration (NOAA), 2009
S. Hemisphere Ground (1871-1978 AD)
S.HEMI Land-Ocean Temperature Index in 0.01 degrees Celsius base period: 1951-1980
sources: GHCN 1880-12/2009 + SST: 1880-11/1981 HadISST1 12/1981-12/2009 Reynolds v2 using elimination of outliers and homogeneity adjustment
Notes: 1950 DJF = Dec 1949 - Feb 1950
Vostok Ice Core (1812 AD -422,766 years B.P.)
Historical Isotopic Temperature Record from the Vostok Ice Core
The data available from CDIAC represent a major effort by researchers from France, Russia, and the U.S.A. Jouzel, J., C. Lorius, J.R. Petit, C. Genthon, N.I. Barkov,
V.M. Kotlyakov, and V.M. Petrov. 1987. Vostok ice core: a continuous sotope temperature record over the last climatic cycle (160,000 years). Nature 329:403-8.
Jouzel, J., N.I. Barkov, J.M. Barnola, M. Bender, J. Chappellaz,C. Genthon, V.M. Kotlyakov, V. Lipenkov, C. Lorius, J.R. Petit,D. Raynaud, G. Raisbeck, C. Ritz, T. Sowers, M. Stievenard, F. Yiou, and P. Yiou. 1993.
Extending the Vostok ice-core record of palaeoclimate to the penultimate glacial period. Nature 364:407-12
Jouzel, J., C. Waelbroeck, B. Malaize, M. Bender, J.R. Petit, M. Stievenard, N.I. Barkov, J.M. Barnola, T. King, V.M. Kotlyakov,V. Lipenkov, C. Lorius, D. Raynaud, C. Ritz, and T. Sowers. 1996.
Climatic interpretation of the recently extended Vostok ice records.
Climate Dynamics 12:513-521.
Petit, J.R., J. Jouzel, D. Raynaud, N.I. Barkov, J.-M. Barnola, I. Basile, M. Bender, J. Chappellaz, M. Davis, G. Delayque, M. Delmotte, V.M. Kotlyakov, M. Legrand, V.Y. Lipenkov, C. Lorius, L. Pepin, C. Ritz, E. Saltzman, and M. Stievenard. 1999.
Climate and atmospheric history of the past 420,000 years from the Vostok ice core, Antarctica. Nature 399: 429-436.
Source: J. R. Petit, D. Raynaud, C. Lorius
Laboratoire de Glaciologie et de Geophysique de l'Environnement
38402 Saint Martin d'Heres Cedex, France
J. Jouzel, G. Delaygue
Laboratoire des Sciences du Climat et de l'Environment
(UMR CEA/CNRS 1572)
91191 Gif-sur-Yvette Cedex, France
N. I. Barkov
Arctic and Antarctic Research Institute
Beringa Street 38
St. Petersburg 199397, Russia
V. M. Kotlyakov
Institute of Geography
Staromonetny, per 29, Moscow 109017, Russia
January 2000
cannawizard
Well-Known Member
**nice post Joe'.. interesting stuff on c02 records... i bet plants around the jurassic period probably had ppms near what im giving my plants.. lol..
cannawizard
Well-Known Member
**something about chicks w/ balls dont fly with me either.. lmfao
cannawizard
Well-Known Member
**almost got tempted to say something about kessils in WeJuanas thread, but ish coo... i'll keep my kessil secrets locked deep within this thread .. lolrofl hahahahahaha, u wait til these seeds are done man, then we gonna light up a monster fatty blunt, imma roll one whole plant into it loland we gonna get fucked up and watch the seeds dry lol
cannawizard
Well-Known Member
[video=youtube;JWMq4Xsmi8o]http://www.youtube.com/watch?v=JWMq4Xsmi8o&feature=related[/video]
...west coast...........
<3
...west coast...........
<3
cannawizard
Well-Known Member
**just depleted the c02 tanks... 5000ppm / 60-50%rwh / 74f (3 days straight / 20on-4off)
--growth examined seemed "great"
--no stress, nothing visually on Psurface indicating any DEFs..
--ultra-high c02 levels adversely affecting Cannabis... at this point (imo) ..No
--20+ strains tested
--growth examined seemed "great"
--no stress, nothing visually on Psurface indicating any DEFs..
--ultra-high c02 levels adversely affecting Cannabis... at this point (imo) ..No
--20+ strains tested
cannawizard
Well-Known Member
View attachment 1858722
**i like my ladies w/ curves
View attachment 1858710View attachment 1858708View attachment 1858720View attachment 1858719View attachment 1858718View attachment 1858715View attachment 1858704View attachment 1858707
---another day another bong load
[video=youtube;6PN78PS_QsM]http://www.youtube.com/watch?v=6PN78PS_QsM[/video]
**i like my ladies w/ curves
View attachment 1858710View attachment 1858708View attachment 1858720View attachment 1858719View attachment 1858718View attachment 1858715View attachment 1858704View attachment 1858707
---another day another bong load
[video=youtube;6PN78PS_QsM]http://www.youtube.com/watch?v=6PN78PS_QsM[/video]
cannawizard
Well-Known Member
**clinical depression is now on my list of thanks :\ ..no more last minute trying of synthetic drugs.. sticking to ONLY Cannabis till the day im worm-casting
Illumination
New Member
What about during flower? Have read that diminished levels of co2 in flower, especially later in flower, increase potency and/or trichome production. Also being that obviously you have really well sealed environment this begs the question, do you also supplement oxygen ? In my thoughts it seems they would produce enough o2 during lights on to carry their requirements during lights out. But I have read of those which also supplement o2 during lights out has been rewarded with greater yield but am skeptical, so picking your brain and experience here. Thanx bunches in advance.
Namaste'
cannawizard
Well-Known Member
**i try to maintain the same ratio during flower but really 1500kppm is all you need to get nice juicy flowers... But... that doesnt answer squat on our ends... seems like its gonna just trial&error, lets see the results
cannawizard
Well-Known Member
High CO2 boosts plant respiration, potentially affecting climate and crops
Posted on February 9, 2009
by Anthony Watts
Here’s something you don’t see everyday: a university sending out a press release showing the potential benefits on crop yields of elevated atmospheric CO2 levels. – Anthony
Public release date: 9-Feb-2009
http://www.eurekalert.org/pub_releases/2009-02/uoia-hcb020609.php
Contact: Diana Yates
[email protected]
217-333-5802
University of Illinois at Urbana-Champaign
High CO2 boosts plant respiration, potentially affecting climate and crops
The leaves of soybeans grown at the elevated carbon dioxide (CO2) levels predicted for the year 2050 respire more than those grown under current atmospheric conditions, researchers report, a finding that will help fine-tune climate models and could point to increased crop yields as CO2 levels rise. The study, from researchers at the University of Illinois and the U.S. Dept. of Agriculture, appears this week in the Proceedings of the National Academy of Sciences. Plants draw CO2 from the atmosphere and make sugars through the process of photosynthesis. But they also release some CO2 during respiration as they use the sugars to generate energy for self-maintenance and growth. How elevated CO2 affects plant respiration will therefore influence future food supplies and the extent to which plants can capture CO2 from the air and store it as carbon in their tissues. While there is broad agreement that higher atmospheric CO2 levels stimulate photosynthesis in C3 plants, such as soybean, no such consensus exists on how rising CO2 levels will affect plant respiration.
IMAGE: Andrew Leakey and assistants at work in the Soy FACE facility at Illinois.
Click here for more information.
“There’s been a great deal of controversy about how plant respiration responds to elevated CO2,” said U. of I. plant biology professor Andrew Leakey, who led the study. “Some summary studies suggest it will go down by 18 percent, some suggest it won’t change, and some suggest it will increase as much as 11 percent.” Understanding how the respiratory pathway responds when plants are grown at elevated CO2 is key to reducing this uncertainty, Leakey said.
His team used microarrays, a genomic tool that can detect changes in the activity of thousands of genes at a time, to learn which genes in the high CO2 plants were being switched on at higher or lower levels than those of the soybeans grown at current CO2 levels. Rather than assessing plants grown in chambers in a greenhouse, as most studies have done, Leakey’s team made use of the Soybean Free Air Concentration Enrichment (Soy FACE) facility at Illinois. This open-air research lab can expose a soybean field to a variety of atmospheric CO2 levels – without isolating the plants from other environmental influences, such as rainfall, sunlight and insects. Some of the plants were exposed to atmospheric CO2 levels of 550 parts per million (ppm), the level predicted for the year 2050 if current trends continue. These were compared to plants grown at ambient CO2 levels (380 ppm).
The results were striking. At least 90 different genes coding the majority of enzymes in the cascade of chemical reactions that govern respiration were switched on (expressed) at higher levels in the soybeans grown at high CO2 levels. This explained how the plants were able to use the increased supply of sugars from stimulated photosynthesis under high CO2 conditions to produce energy, Leakey said. The rate of respiration increased 37 percent at the elevated CO2 levels. The enhanced respiration is likely to support greater transport of sugars from leaves to other growing parts of the plant, including the seeds, Leakey said. “The expression of over 600 genes was altered by elevated CO2 in total, which will help us to understand how the response is regulated and also hopefully produce crops that will perform better in the future,” he said.
IMAGE: Illinois plant biology professor Andrew Leakey led a team that discovered that soybean leaves speed up their metabolism in response to rising CO2. Click here for more information.
Posted on February 9, 2009
by Anthony Watts
Here’s something you don’t see everyday: a university sending out a press release showing the potential benefits on crop yields of elevated atmospheric CO2 levels. – Anthony
Public release date: 9-Feb-2009
http://www.eurekalert.org/pub_releases/2009-02/uoia-hcb020609.php
Contact: Diana Yates
[email protected]
217-333-5802
University of Illinois at Urbana-Champaign
High CO2 boosts plant respiration, potentially affecting climate and crops
The leaves of soybeans grown at the elevated carbon dioxide (CO2) levels predicted for the year 2050 respire more than those grown under current atmospheric conditions, researchers report, a finding that will help fine-tune climate models and could point to increased crop yields as CO2 levels rise. The study, from researchers at the University of Illinois and the U.S. Dept. of Agriculture, appears this week in the Proceedings of the National Academy of Sciences. Plants draw CO2 from the atmosphere and make sugars through the process of photosynthesis. But they also release some CO2 during respiration as they use the sugars to generate energy for self-maintenance and growth. How elevated CO2 affects plant respiration will therefore influence future food supplies and the extent to which plants can capture CO2 from the air and store it as carbon in their tissues. While there is broad agreement that higher atmospheric CO2 levels stimulate photosynthesis in C3 plants, such as soybean, no such consensus exists on how rising CO2 levels will affect plant respiration.
IMAGE: Andrew Leakey and assistants at work in the Soy FACE facility at Illinois. Click here for more information.
“There’s been a great deal of controversy about how plant respiration responds to elevated CO2,” said U. of I. plant biology professor Andrew Leakey, who led the study. “Some summary studies suggest it will go down by 18 percent, some suggest it won’t change, and some suggest it will increase as much as 11 percent.” Understanding how the respiratory pathway responds when plants are grown at elevated CO2 is key to reducing this uncertainty, Leakey said.
His team used microarrays, a genomic tool that can detect changes in the activity of thousands of genes at a time, to learn which genes in the high CO2 plants were being switched on at higher or lower levels than those of the soybeans grown at current CO2 levels. Rather than assessing plants grown in chambers in a greenhouse, as most studies have done, Leakey’s team made use of the Soybean Free Air Concentration Enrichment (Soy FACE) facility at Illinois. This open-air research lab can expose a soybean field to a variety of atmospheric CO2 levels – without isolating the plants from other environmental influences, such as rainfall, sunlight and insects. Some of the plants were exposed to atmospheric CO2 levels of 550 parts per million (ppm), the level predicted for the year 2050 if current trends continue. These were compared to plants grown at ambient CO2 levels (380 ppm).
The results were striking. At least 90 different genes coding the majority of enzymes in the cascade of chemical reactions that govern respiration were switched on (expressed) at higher levels in the soybeans grown at high CO2 levels. This explained how the plants were able to use the increased supply of sugars from stimulated photosynthesis under high CO2 conditions to produce energy, Leakey said. The rate of respiration increased 37 percent at the elevated CO2 levels. The enhanced respiration is likely to support greater transport of sugars from leaves to other growing parts of the plant, including the seeds, Leakey said. “The expression of over 600 genes was altered by elevated CO2 in total, which will help us to understand how the response is regulated and also hopefully produce crops that will perform better in the future,” he said.
IMAGE: Illinois plant biology professor Andrew Leakey led a team that discovered that soybean leaves speed up their metabolism in response to rising CO2. Click here for more information.
cannawizard
Well-Known Member
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Climate Change Surprise: High Carbon Dioxide Levels Can Retard Plant Growth, Study Reveals
ScienceDaily (Dec. 6, 2002) — The prevailing view among scientists is that global climate change may prove beneficial to many farmers and foresters – at least in the short term. The logic is straightforward: Plants need atmospheric carbon dioxide to produce food, and by emitting more CO2 into the air, our cars and factories create new sources of plant nutrition that will cause some crops and trees to grow bigger and faster. But an unprecedented three-year experiment conducted at Stanford University is raising questions about that long-held assumption. Writing in the journal Science, researchers concluded that elevated atmospheric CO2 actually reduces plant growth when combined with other likely consequences of climate change – namely, higher temperatures, increased precipitation or increased nitrogen deposits in the soil.
See Also:
Plants & Animals
Earth & Climate
Reference
The results of the study may prompt researchers and policymakers to re-think one of the standard arguments against taking action to prevent global warming: that natural ecosystems will minimize the problem of fossil fuel emissions by transferring large amounts of carbon in the atmosphere to plants and soils.
"Perhaps we won't get as much help with the carbon problem as we thought we could, and we will need to put more emphasis on both managing vegetation and reducing emissions," said Harold A. Mooney, the Paul S. Achilles Professor of Environmental Biology at Stanford and co-author of the Dec. 6 Science study.
He noted that the Stanford study is the first ecosystem-scale experiment to apply four climate change factors across several generations of plants.
"To understand complex ecological systems, the traditional approach of isolating one factor and looking at that response, then extrapolating to the whole system, is often not correct," Mooney said. "On an ecosystem scale, many interacting factors may be involved."
Jasper Ridge Global Change Project
The findings published in Science are among the first results of the Jasper Ridge Global Change Project – a multi-year experiment designed to demonstrate how a typical California grassland ecosystem will respond to future global environmental changes.
Located in a fenced off section of Stanford's 1,189-acre Jasper Ridge Biological Preserve, the novel experiment was designed to simulate environmental conditions that climate experts predict may exist 100 years from now: a doubling of atmospheric CO2; a temperature rise of 2 degrees F; a 50 percent increase in precipitation; and increased nitrogen deposition – largely a byproduct of fossil fuel burning.
Launched in 1997, the Jasper Ridge experiment was conceived by Mooney and Christopher B. Field, a professor by courtesy in Stanford's Department of Biological Sciences and director of the Carnegie Institution's Department of Global Ecology, also located on the Stanford campus.
"Most studies have looked at the effects of CO2 on plants in pots or on very simple ecosystems and concluded that plants are going to grow faster in the future," said Field, co-author of the Science study. "We got exactly the same results when we applied CO2 alone, but when we factored in realistic treatments – warming, changes in nitrogen deposition, changes in precipitation – growth was actually suppressed."
To mimic future climate conditions, Field, Mooney and their colleagues mapped out 36 circular plots of land, each about six feet in diameter. Four plots are virtually untouched, receiving no additional water, nitrogen, carbon dioxide or heat. Each of the remaining 32 circles is divided into four equal quadrants separated by underground partitions to prevent roots in one section from invading neighboring tracts. In these smaller quadrants, researchers study all 16 possible combinations of elevated and normal CO2, heat, water and nitrogen.
The plots thicken
The biggest surprise from the study was the discovery that elevated carbon dioxide only stimulated plant growth when nitrogen, water and temperature were kept at normal levels.
"Based on earlier single-treatment studies with elevated CO2, we initially hypothesized that, with the combination of all four treatments together, the response would be additional growth," said W. Rebecca Shaw, a researcher with the Nature Conservancy of California and lead author of the Science study.
But results from the third year of the experiment revealed a more complex scenario. While treatments involving increased temperature, nitrogen deposition or precipitation – alone or in combination – promoted plant growth, the addition of elevated CO2 consistently dampened those increases.
"The three-factor combination of increased temperature, precipitation and nitrogen deposition produced the largest stimulation [an 84 percent increase], but adding CO2 reduced this to 40 percent," Shaw and her colleagues wrote.
The mean net plant growth for all treatment combinations with elevated CO2 was about 4.9 tons per acre – compared to roughly 5.5 tons per acre for all treatment combinations in which CO2 levels were kept normal. However, when higher amounts of CO2 gas were added to plots with normal temperature, moisture and nitrogen levels, aboveground plant growth increased by nearly a third.
Why would elevated CO2 in combination with other factors have a suppressive effect on plant growth? The researchers aren't sure, but one possibility is that excess carbon in the soil is allowing microbes to outcompete plants for one or more limiting nutrients.
"By applying all four treatments, we may be repositioning the ecosystem so that another environmental factor becomes limiting to growth," Field observed. "For example, by increasing plant growth as a result of adding water or nitrogen, the ecosystem may become more sensitive to limitation by another mineral nutrient such as phosphorus, potassium or something else we hadn't been measuring."
A new five-year experiment is underway at the Jasper Ridge site to analyze potential limiting nutrients in the soil along with microbial-plant interactions and the molecular biology of the vegetation.
Policy implications
Field and his colleagues say that their ultimate goal is to use the results of the Jasper Ridge study to forecast what will happen to other ecosystems – from alpine tundra to tropical rainforests.
"In the past, people have argued that perhaps we don't really need to worry about fossil fuel emissions, because increased plant growth will effectively pull elevated CO2 concentrations out of the atmosphere and keep the world at the appropriate equilibrium," he added. "But our experiment shows that we can't count on the natural world, the unmanaged world, to save us by pulling down all the atmospheric CO2."
Added Mooney: "Our study demonstrates that there is still a lot to learn about the factors that regulate global climate change. But we also know a lot already, more than enough to engage in a serious discussion about action to reduce CO2 emissions from burning fossil fuels and clearing forests."
Other coauthors of the Science study are former Stanford doctoral student Erika S. Zavaleta, now a Nature Conservancy post-doctoral fellow at the University of California-Berkeley; Nona R. Chiariello, research coordinator of Stanford's Jasper Ridge Biological Preserve; and Elsa E. Cleland, a graduate student in the Stanford Department of Biological Sciences.
The study was supported by the National Science Foundation, the Morgan Family Foundation, the David and Lucile Packard Foundation, the Jasper Ridge Biological Preserve, the Carnegie Institution of Washington, the U.S. Department of Energy, the U.S. Environmental Protection Agency, the Switzer Foundation and the A.W. Mellon Foundation.
Blog Cite Save Email Print ShareClimate Change Surprise: High Carbon Dioxide Levels Can Retard Plant Growth, Study Reveals
ScienceDaily (Dec. 6, 2002) — The prevailing view among scientists is that global climate change may prove beneficial to many farmers and foresters – at least in the short term. The logic is straightforward: Plants need atmospheric carbon dioxide to produce food, and by emitting more CO2 into the air, our cars and factories create new sources of plant nutrition that will cause some crops and trees to grow bigger and faster. But an unprecedented three-year experiment conducted at Stanford University is raising questions about that long-held assumption. Writing in the journal Science, researchers concluded that elevated atmospheric CO2 actually reduces plant growth when combined with other likely consequences of climate change – namely, higher temperatures, increased precipitation or increased nitrogen deposits in the soil.
See Also:
Plants & Animals
Earth & Climate
Reference
- Consensus of scientists regarding global warming
- Scientific opinion on climate change
- Ocean acidification
- Fossil fuel
The results of the study may prompt researchers and policymakers to re-think one of the standard arguments against taking action to prevent global warming: that natural ecosystems will minimize the problem of fossil fuel emissions by transferring large amounts of carbon in the atmosphere to plants and soils.
"Perhaps we won't get as much help with the carbon problem as we thought we could, and we will need to put more emphasis on both managing vegetation and reducing emissions," said Harold A. Mooney, the Paul S. Achilles Professor of Environmental Biology at Stanford and co-author of the Dec. 6 Science study.
He noted that the Stanford study is the first ecosystem-scale experiment to apply four climate change factors across several generations of plants.
"To understand complex ecological systems, the traditional approach of isolating one factor and looking at that response, then extrapolating to the whole system, is often not correct," Mooney said. "On an ecosystem scale, many interacting factors may be involved."
Jasper Ridge Global Change Project
The findings published in Science are among the first results of the Jasper Ridge Global Change Project – a multi-year experiment designed to demonstrate how a typical California grassland ecosystem will respond to future global environmental changes.
Located in a fenced off section of Stanford's 1,189-acre Jasper Ridge Biological Preserve, the novel experiment was designed to simulate environmental conditions that climate experts predict may exist 100 years from now: a doubling of atmospheric CO2; a temperature rise of 2 degrees F; a 50 percent increase in precipitation; and increased nitrogen deposition – largely a byproduct of fossil fuel burning.
Launched in 1997, the Jasper Ridge experiment was conceived by Mooney and Christopher B. Field, a professor by courtesy in Stanford's Department of Biological Sciences and director of the Carnegie Institution's Department of Global Ecology, also located on the Stanford campus.
"Most studies have looked at the effects of CO2 on plants in pots or on very simple ecosystems and concluded that plants are going to grow faster in the future," said Field, co-author of the Science study. "We got exactly the same results when we applied CO2 alone, but when we factored in realistic treatments – warming, changes in nitrogen deposition, changes in precipitation – growth was actually suppressed."
To mimic future climate conditions, Field, Mooney and their colleagues mapped out 36 circular plots of land, each about six feet in diameter. Four plots are virtually untouched, receiving no additional water, nitrogen, carbon dioxide or heat. Each of the remaining 32 circles is divided into four equal quadrants separated by underground partitions to prevent roots in one section from invading neighboring tracts. In these smaller quadrants, researchers study all 16 possible combinations of elevated and normal CO2, heat, water and nitrogen.
The plots thicken
The biggest surprise from the study was the discovery that elevated carbon dioxide only stimulated plant growth when nitrogen, water and temperature were kept at normal levels.
"Based on earlier single-treatment studies with elevated CO2, we initially hypothesized that, with the combination of all four treatments together, the response would be additional growth," said W. Rebecca Shaw, a researcher with the Nature Conservancy of California and lead author of the Science study.
But results from the third year of the experiment revealed a more complex scenario. While treatments involving increased temperature, nitrogen deposition or precipitation – alone or in combination – promoted plant growth, the addition of elevated CO2 consistently dampened those increases.
"The three-factor combination of increased temperature, precipitation and nitrogen deposition produced the largest stimulation [an 84 percent increase], but adding CO2 reduced this to 40 percent," Shaw and her colleagues wrote.
The mean net plant growth for all treatment combinations with elevated CO2 was about 4.9 tons per acre – compared to roughly 5.5 tons per acre for all treatment combinations in which CO2 levels were kept normal. However, when higher amounts of CO2 gas were added to plots with normal temperature, moisture and nitrogen levels, aboveground plant growth increased by nearly a third.
Why would elevated CO2 in combination with other factors have a suppressive effect on plant growth? The researchers aren't sure, but one possibility is that excess carbon in the soil is allowing microbes to outcompete plants for one or more limiting nutrients.
"By applying all four treatments, we may be repositioning the ecosystem so that another environmental factor becomes limiting to growth," Field observed. "For example, by increasing plant growth as a result of adding water or nitrogen, the ecosystem may become more sensitive to limitation by another mineral nutrient such as phosphorus, potassium or something else we hadn't been measuring."
A new five-year experiment is underway at the Jasper Ridge site to analyze potential limiting nutrients in the soil along with microbial-plant interactions and the molecular biology of the vegetation.
Policy implications
Field and his colleagues say that their ultimate goal is to use the results of the Jasper Ridge study to forecast what will happen to other ecosystems – from alpine tundra to tropical rainforests.
"In the past, people have argued that perhaps we don't really need to worry about fossil fuel emissions, because increased plant growth will effectively pull elevated CO2 concentrations out of the atmosphere and keep the world at the appropriate equilibrium," he added. "But our experiment shows that we can't count on the natural world, the unmanaged world, to save us by pulling down all the atmospheric CO2."
Added Mooney: "Our study demonstrates that there is still a lot to learn about the factors that regulate global climate change. But we also know a lot already, more than enough to engage in a serious discussion about action to reduce CO2 emissions from burning fossil fuels and clearing forests."
Other coauthors of the Science study are former Stanford doctoral student Erika S. Zavaleta, now a Nature Conservancy post-doctoral fellow at the University of California-Berkeley; Nona R. Chiariello, research coordinator of Stanford's Jasper Ridge Biological Preserve; and Elsa E. Cleland, a graduate student in the Stanford Department of Biological Sciences.
The study was supported by the National Science Foundation, the Morgan Family Foundation, the David and Lucile Packard Foundation, the Jasper Ridge Biological Preserve, the Carnegie Institution of Washington, the U.S. Department of Energy, the U.S. Environmental Protection Agency, the Switzer Foundation and the A.W. Mellon Foundation.
cannawizard
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High Carbon Dioxide Boosts Plant Respiration, Potentially Affecting Climate And Crops
ScienceDaily (Feb. 9, 2009) — The leaves of soybeans grown at the elevated carbon dioxide (CO2) levels predicted for the year 2050 respire more than those grown under current atmospheric conditions, researchers report, a finding that will help fine-tune climate models and could point to increased crop yields as CO2 levels rise.
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Plants & Animals
Earth & Climate
Reference
The study, from researchers at the University of Illinois and the U.S. Dept. of Agriculture, appears the week of February 9 in the Proceedings of the National Academy of Sciences.
Plants draw CO2 from the atmosphere and make sugars through the process of photosynthesis. But they also release some CO2 during respiration as they use the sugars to generate energy for self-maintenance and growth. How elevated CO2 affects plant respiration will therefore influence future food supplies and the extent to which plants can capture CO2 from the air and store it as carbon in their tissues.
While there is broad agreement that higher atmospheric CO2 levels stimulate photosynthesis in C3 plants, such as soybean, no such consensus exists on how rising CO2 levels will affect plant respiration.
"There's been a great deal of controversy about how plant respiration responds to elevated CO2," said U. of I. plant biology professor Andrew Leakey, who led the study. "Some summary studies suggest it will go down by 18 percent, some suggest it won't change, and some suggest it will increase as much as 11 percent."
Understanding how the respiratory pathway responds when plants are grown at elevated CO2 is key to reducing this uncertainty, Leakey said. His team used microarrays, a genomic tool that can detect changes in the activity of thousands of genes at a time, to learn which genes in the high CO2 plants were being switched on at higher or lower levels than those of the soybeans grown at current CO2 levels.
Rather than assessing plants grown in chambers in a greenhouse, as most studies have done, Leakey's team made use of the Soybean Free Air Concentration Enrichment (Soy FACE) facility at Illinois. This open-air research lab can expose a soybean field to a variety of atmospheric CO2 levels – without isolating the plants from other environmental influences, such as rainfall, sunlight and insects.
Some of the plants were exposed to atmospheric CO2 levels of 550 parts per million (ppm), the level predicted for the year 2050 if current trends continue. These were compared to plants grown at ambient CO2 levels (380 ppm).
The results were striking. At least 90 different genes coding the majority of enzymes in the cascade of chemical reactions that govern respiration were switched on (expressed) at higher levels in the soybeans grown at high CO2 levels. This explained how the plants were able to use the increased supply of sugars from stimulated photosynthesis under high CO2 conditions to produce energy, Leakey said. The rate of respiration increased 37 percent at the elevated CO2 levels.
The enhanced respiration is likely to support greater transport of sugars from leaves to other growing parts of the plant, including the seeds, Leakey said.
"The expression of over 600 genes was altered by elevated CO2 in total, which will help us to understand how the response is regulated and also hopefully produce crops that will perform better in the future," he said.
Leakey is also an affiliate of the Institute for Genomic Biology at Illinois.
Blog Cite Save Email Print ShareHigh Carbon Dioxide Boosts Plant Respiration, Potentially Affecting Climate And Crops
ScienceDaily (Feb. 9, 2009) — The leaves of soybeans grown at the elevated carbon dioxide (CO2) levels predicted for the year 2050 respire more than those grown under current atmospheric conditions, researchers report, a finding that will help fine-tune climate models and could point to increased crop yields as CO2 levels rise.
See Also:
Plants & Animals
Earth & Climate
Reference
The study, from researchers at the University of Illinois and the U.S. Dept. of Agriculture, appears the week of February 9 in the Proceedings of the National Academy of Sciences.
Plants draw CO2 from the atmosphere and make sugars through the process of photosynthesis. But they also release some CO2 during respiration as they use the sugars to generate energy for self-maintenance and growth. How elevated CO2 affects plant respiration will therefore influence future food supplies and the extent to which plants can capture CO2 from the air and store it as carbon in their tissues.
While there is broad agreement that higher atmospheric CO2 levels stimulate photosynthesis in C3 plants, such as soybean, no such consensus exists on how rising CO2 levels will affect plant respiration.
"There's been a great deal of controversy about how plant respiration responds to elevated CO2," said U. of I. plant biology professor Andrew Leakey, who led the study. "Some summary studies suggest it will go down by 18 percent, some suggest it won't change, and some suggest it will increase as much as 11 percent."
Understanding how the respiratory pathway responds when plants are grown at elevated CO2 is key to reducing this uncertainty, Leakey said. His team used microarrays, a genomic tool that can detect changes in the activity of thousands of genes at a time, to learn which genes in the high CO2 plants were being switched on at higher or lower levels than those of the soybeans grown at current CO2 levels.
Rather than assessing plants grown in chambers in a greenhouse, as most studies have done, Leakey's team made use of the Soybean Free Air Concentration Enrichment (Soy FACE) facility at Illinois. This open-air research lab can expose a soybean field to a variety of atmospheric CO2 levels – without isolating the plants from other environmental influences, such as rainfall, sunlight and insects.
Some of the plants were exposed to atmospheric CO2 levels of 550 parts per million (ppm), the level predicted for the year 2050 if current trends continue. These were compared to plants grown at ambient CO2 levels (380 ppm).
The results were striking. At least 90 different genes coding the majority of enzymes in the cascade of chemical reactions that govern respiration were switched on (expressed) at higher levels in the soybeans grown at high CO2 levels. This explained how the plants were able to use the increased supply of sugars from stimulated photosynthesis under high CO2 conditions to produce energy, Leakey said. The rate of respiration increased 37 percent at the elevated CO2 levels.
The enhanced respiration is likely to support greater transport of sugars from leaves to other growing parts of the plant, including the seeds, Leakey said.
"The expression of over 600 genes was altered by elevated CO2 in total, which will help us to understand how the response is regulated and also hopefully produce crops that will perform better in the future," he said.
Leakey is also an affiliate of the Institute for Genomic Biology at Illinois.
cannawizard
Well-Known Member
Climate myths: Higher CO2 levels will boost plant growth and food production
According to some accounts, the rise in carbon dioxide will usher in a new golden age where food production will be higher than ever before and most plants and animals will thrive as never before. If it sounds too good to be true, that's because it is.
CO2 is the source of the carbon that plants turn into organic compounds, and it is well established that higher CO2 levels can have a fertilising effect on many plants, boosting growth by as much as a third.
However, some plants already have mechanisms for concentrating CO2 in their tissues, known as C4 photosynthesis, so higher CO2 will not boost the growth of C4 plants.
Where water is a limiting factor, all plants could benefit. Plants lose water through the pores in leaves that let CO2 enter. Higher CO2 levels mean they do not need to open these pores as much, reducing water loss.
However, it is extremely difficult to generalise about the overall impact of the fertilisation effect on plant growth. Numerous groups around the world have been conducting experiments in which plots of land are supplied with enhanced CO2, while comparable nearby plots remain at normal levels.
These experiments suggest that higher CO2 levels could boost the yields of non-C4 crops by around 13 per cent.
Limiting factors
However, while experiments on natural ecosystems have also found initial elevations in the rate of plant growth, these have tended to level off within a few years. In most cases this has been found to be the result of some other limiting factor, such as the availability of nitrogen or water.
The regional climate changes that higher CO2 will bring, and their effect on these limiting factors on plant growth, such as water, also have to be taken into account. These indirect effects are likely to have a much larger impact than CO2 fertilisation.
For instance, while higher temperatures will boost plant growth in cooler regions, in the tropics they may actually impede growth. A two-decade study of rainforest plots in Panama and Malaysia recently concluded that local temperature rises of more than 1ºC have reduced tree growth by 50 per cent (see Don't count on the trees).
Another complicating factor is ground level ozone due to air pollution, which damages plants. This is expected to rise in many regions over the coming decades and could reduce or even negate the beneficial effects of higher CO2 (see Climate change warning over food production).
In the oceans, increased CO2 is causing acidification of water. Recent research has shown that the expected doubling of CO2 concentrations could inhibit the development of some calcium-shelled organisms, including phytoplankton, which are at the base of a large and complex marine ecosystem (see Ocean acidification: the other CO2 problem). That may also result in significant loss of biodiversity, possibly including important food species.
Levelling off
Some have suggested that the increase in plant growth due to CO2 will be so great that it soaks up much of the extra CO2 from the burning of fossil fuels, significantly slowing climate change. But higher plant growth will only lock away CO2 if there is an accumulation of organic matter.
Studies of past climate changes suggest the land and oceans start releasing more CO2 than they absorb as the planet warms. The latest IPCC report concludes that the terrestrial biosphere will become a source rather than a sink of carbon before the end of the century.
What's more, even if plant growth does rise overall, the direct and indirect effects of higher CO2 levels will be disastrous for biodiversity. Between 20 to 30% of plant and animal species face extinction by the end of the century, according to the IPCC report.
As for food crops, the factors are more complex. The crops most widely used in the world for food in many cases depend on particular combinations of soil type, climate, moisture, weather patterns and the infrastructure of equipment, experience and distribution systems. If the climate warms so much that crops no longer thrive in their traditional settings, farming of some crops may be able to shift to adjacent areas, but others may not. Rich farmers and countries will be able to adapt more easily than poorer ones.
Predicting the world's overall changes in food production in response to elevated CO2 is virtually impossible. Global production is expected to rise until the increase in local average temperatures exceeds 3°C, but then start to fall. In tropical and dry regions increases of just 1 to 2°C are expected to lead to falls in production. In marginal lands where water is the greatest constraint, which includes much of the developing world but also regions such as the western US, the losses may greatly exceed the gains
- 17:00 16 May 2007 by David Chandler and Michael Le Page
- For similar stories, visit the Climate Change Topic Guide
According to some accounts, the rise in carbon dioxide will usher in a new golden age where food production will be higher than ever before and most plants and animals will thrive as never before. If it sounds too good to be true, that's because it is.
CO2 is the source of the carbon that plants turn into organic compounds, and it is well established that higher CO2 levels can have a fertilising effect on many plants, boosting growth by as much as a third.
However, some plants already have mechanisms for concentrating CO2 in their tissues, known as C4 photosynthesis, so higher CO2 will not boost the growth of C4 plants.
Where water is a limiting factor, all plants could benefit. Plants lose water through the pores in leaves that let CO2 enter. Higher CO2 levels mean they do not need to open these pores as much, reducing water loss.
However, it is extremely difficult to generalise about the overall impact of the fertilisation effect on plant growth. Numerous groups around the world have been conducting experiments in which plots of land are supplied with enhanced CO2, while comparable nearby plots remain at normal levels.
These experiments suggest that higher CO2 levels could boost the yields of non-C4 crops by around 13 per cent.
Limiting factors
However, while experiments on natural ecosystems have also found initial elevations in the rate of plant growth, these have tended to level off within a few years. In most cases this has been found to be the result of some other limiting factor, such as the availability of nitrogen or water.
The regional climate changes that higher CO2 will bring, and their effect on these limiting factors on plant growth, such as water, also have to be taken into account. These indirect effects are likely to have a much larger impact than CO2 fertilisation.
For instance, while higher temperatures will boost plant growth in cooler regions, in the tropics they may actually impede growth. A two-decade study of rainforest plots in Panama and Malaysia recently concluded that local temperature rises of more than 1ºC have reduced tree growth by 50 per cent (see Don't count on the trees).
Another complicating factor is ground level ozone due to air pollution, which damages plants. This is expected to rise in many regions over the coming decades and could reduce or even negate the beneficial effects of higher CO2 (see Climate change warning over food production).
In the oceans, increased CO2 is causing acidification of water. Recent research has shown that the expected doubling of CO2 concentrations could inhibit the development of some calcium-shelled organisms, including phytoplankton, which are at the base of a large and complex marine ecosystem (see Ocean acidification: the other CO2 problem). That may also result in significant loss of biodiversity, possibly including important food species.
Levelling off
Some have suggested that the increase in plant growth due to CO2 will be so great that it soaks up much of the extra CO2 from the burning of fossil fuels, significantly slowing climate change. But higher plant growth will only lock away CO2 if there is an accumulation of organic matter.
Studies of past climate changes suggest the land and oceans start releasing more CO2 than they absorb as the planet warms. The latest IPCC report concludes that the terrestrial biosphere will become a source rather than a sink of carbon before the end of the century.
What's more, even if plant growth does rise overall, the direct and indirect effects of higher CO2 levels will be disastrous for biodiversity. Between 20 to 30% of plant and animal species face extinction by the end of the century, according to the IPCC report.
As for food crops, the factors are more complex. The crops most widely used in the world for food in many cases depend on particular combinations of soil type, climate, moisture, weather patterns and the infrastructure of equipment, experience and distribution systems. If the climate warms so much that crops no longer thrive in their traditional settings, farming of some crops may be able to shift to adjacent areas, but others may not. Rich farmers and countries will be able to adapt more easily than poorer ones.
Predicting the world's overall changes in food production in response to elevated CO2 is virtually impossible. Global production is expected to rise until the increase in local average temperatures exceeds 3°C, but then start to fall. In tropical and dry regions increases of just 1 to 2°C are expected to lead to falls in production. In marginal lands where water is the greatest constraint, which includes much of the developing world but also regions such as the western US, the losses may greatly exceed the gains