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Category: Main/Abstracts/Carbon Cycle Response to Environmental Change


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  HAZARDS OF TEMPERATURE ON FOOD AVAILABILITY IN CHANGING ENVIRONMENTS  Popular
Description:
Global temperatures are predicted to increase from rising levels of atmospheric carbon dioxide (CO2) and other greenhouse gases. We conducted experiments in sunlit, controlled-environment chambers and temperature-gradient greenhouses to determine effects of elevated temperature and doubled CO2 concentration on pollination and yield of rice, soybean, dry bean, peanut, and grain sorghum. Photosynthesis and vegetative growth were more tolerant of increasing temperatures than reproductive processes. Rice seed yields were optimum at 25°C mean daily temperature and decreased with increasing temperature (typically about 10% decline for each 1°C rise in temperature). Grain sorghum yield response to temperature was similar to rice, but dry bean was more sensitive, and soybean and peanut were more tolerant. Pollen viability followed a temperature response similar to seed yield. Comparisons of 43 rice cultivars in temperature-gradient greenhouses showed genetic variation in percent seed-set in response to a 4.5°C increase above ambient temperatures in Florida. Thus, there appears to be a range of adaptation of seed crops to temperature. Elevated CO2 did not prevent high temperature decline in yield; in dry bean it made pollination more sensitive to high temperature. In summary, global warming will be a greater threat to crop seed yields than to photosynthesis and vegetative growth. However, crop genetic improvements might ameliorate part, but not all, of the high temperature hazards for seed yields and global food security.

Author's Names: L.H. Allen, Jr, K.J. Boote, P.V.V. Prasad, J.M.G. Thomas, and J.C.V. Vu
Filesize: 28.20 Kb
Added on: 25-Jul-2005 Downloads: 174
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  GREENHOUSE GAS CO2, CH4 AND CLIMATE EVOLUTION SINCE 650KYRS DEDUCED FROM ANTARCTIC ICE CORES  Popular
Description:

Ice cores are unique archives of past climatic and atmospheric conditions through the isotopic composition of the ice and the analysis of the air bubbles trapped. In 1999 Petit et al published the reconstruction of the Antarctic climate and atmospheric composition over the last 420 000 years from the Vostok ice core. This record covered the last four glacial inter glacial cycles back to the end of the marine interstadial 11 (MIS 11). It has revealed the close relationship between the atmospheric part of the carbon cycle and the climate. With CO2 concentration oscillating between 180 and 280 ppmv during the last 4 climatic cycles. In a similar way the methane concentration followed closely temperature on glacial interglacial time scales, with millennial-scale structures during glacial times which appear out of phased with Antarctic temperature but, at least for the last glaciation, in phase with the Greenland rapid climatic oscillations, as revealed by the GISP and GRIP ice cores.


Author's Names: J.M. Barnola, U. Siegenthaler, et al
Filesize: 15.87 Kb
Added on: 27-Jul-2005 Downloads: 200
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  THE EXPRESSION OF BIOSPHERE RESPONSE TO LIGHT LEVEL CHANGES ON 18O OF ATMOSPHERIC CO2  Popular
Description:

Observations suggest the global reflectivity of Earth changed during recent decades. Although there is some ambiguity surrounding these findings, it is clear that, should there be changes in clouds or scattering aerosols, a change in the total solar radiation received at the surface and the fraction of diffuse light could result. Intriguingly, the d18O of CO2 time series measured at Mauna Loa shows variability during the 1990s that does not match secular trends in CO2 concentration or d13C. While a decrease in total solar radiation alone would reduce biospheric productivity, an increase in diffuse light can increase productivity, as has been argued for the period following the eruption of Pinatubo. Moreover, since the changes in radiation affect the surface latent energy exchange, the isotopic composition of terrestrial water with which CO2 interacts (specifically leaf and soil water) will be modified and can thus drive a change in isotopic fluxes.


Author's Names: N. Buenning, D. Noone, C. Still, W. Riley, et al
Filesize: 227.29 Kb
Added on: 27-Jul-2005 Downloads: 144
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  BIOGEOCHEMICAL CHANGES IN SUBTROPICAL AND SUBPOLAR MODE WATERS: A MINER’S CANARY FOR CLIMATE ... 
Description:

Long-term observations of carbon, nutrients and oxygen in upper thermocline waters, such as subtropical and subpolar mode waters, have revealed substantial interannual to decadal variations. While part of this variability can be ascribed to internal ocean and ecosystem dynamics as well as large-scale climate phenomena (like ENSO, NAO or the PDO), we presently do not know to which extent this variability is influenced by anthropogenic climate change. As a first step to answer this detection question, the impact of natural variability on biogeochemical properties in thermocline waters must be understood and quantified. This permits us then to accurately describe the natural "noise" against which an anthropogenic change needs to be detected. Subtropical and subpolar mode waters may be ideally suited to look at this task since they tend to respond sensitively to climate variations, integrate short-time scale variations over time, and hence exhibit maximum signal to noise ratio. We investigate the role of mode water formation and spreading on interannual to decadal accumulation and release of nutrients and carbon by analyzing results from model runs with the Upper Ocean Model [Danabasoglu and McWilliams 2000] coupled to the ecosystem model of Moore et al. [2002]. We compare results from a run forced with NCEP reanalysis data for the period from 1948 to present with a climatological control run. To better isolate the mechanisms forcing these biogeochemical changes, we compare our results also to a set of experiments in which we manipulate the wind stress forcing and sea surface temperature fields of the model locally.


Author's Names: H. Brix and N. Gruber
Filesize: 92.29 Kb
Added on: 27-Jul-2005 Downloads: 44
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  NEW COUPLED CLIMATE-CARBON SIMULATIONS WITH THE IPSL MODEL: FROM VALIDATION WITH ATMOSPHERIC ...  Popular
Description:

We have developed a Climate-Carbon coupled model based on the IPSL OAGCM and on two biogeochemical models, ORCHIDEE for the continent and PISCES for the ocean, to investigate the coupling between climate change and the global carbon cycle. We have performed four climate-carbon simulations over the 1860-2100 period in which atmospheric CO2 is interactively calculated. They are :

§ A control coupled simulation with no anthropogenic emissions.

§ A coupled simulation with anthropogenic emissions.

§ A coupled simulation with anthropogenic emissions including non-CO2 greenhouse and sulfate aerosols.

§ An uncoupled carbon simulation with the same anthropogenic emissions as second simulation but for which atmospheric CO2 change has no impact on climate.

Compared to the first IPSL Climate-Carbon coupled model [Dufresne, et al., 2002], the simple carbon models have been replaced by IPSL advanced ocean and land biogeochemical models, respectively PISCES and ORCHIDEE. CO2 is transported in the atmosphere and compared with observations. Comparison with satellite data is also done. We then analyze the coupled and uncoupled simulations, highlight the importance of the climate change both on the oceanic and biosphere sink and estimate the climate-carbon feedback. The results are also compared to the outputs of other models participating in the C4MIP inter-comparison project. Finally, off-line simulations are carried out to perform sensitivity tests (fire, dynamics of land and ocean ecosystems, soil respiration) in order to identify the key processes which govern the simulated response.


Author's Names: P. Cadule, P. Friedlingstein and L. Bopp
Filesize: 35.21 Kb
Added on: 27-Jul-2005 Downloads: 183
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  PERSISTENCE OF NITROGEN LIMITATION OVER TERRESTRIAL CARBON UPTAKE  Popular
Description:

Because vegetation growth in the Northern Hemisphere is typically nitrogen-limited, increased nitrogen deposition could have attenuating effect on rising atmospheric CO2 by stimulating the accumulation of biomass. Given the high carbon to nitrogen ratios and long lifetimes of carbon in wood, a most significant effect of nitrogen fertilization is expected in forests. Forest inventories indicate that the carbon content of northern forests have increased concurrently with increased nitrogen deposition since the 1950s [Spiecker et al., 1996]. In addition, variations in atmospheric CO2 indicate a globally significant carbon sink in northern mid-latitude forest regions [Schimel et al., 2001]. It is unclear however, whether elevated nitrogen deposition or other factors are the primary cause of carbon sequestration in northern forests. We argue that the elevated nitrogen deposition is unlikely to enhance vegetation carbon sink significantly because of its differentiating effect on the carbon sequestration capacity of uneven aged forests and climatic limitations on carbon sequestration in the Northern Hemisphere. We estimate the potential of forests with lifted nitrogen limitation to decelerate CO2 concentrations rise in the atmosphere and therefore to mitigate climate warming. We also outline areas of the Northern Hemisphere which are most sensitive to increased nitrogen deposition.


Author's Names: G. Churkina, M. Vetter, and K. Trusilova
Filesize: 135.93 Kb
Added on: 28-Jul-2005 Downloads: 173
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  EUROPEAN-WIDE REDUCTION IN PRIMARY PRODUCTIVITY CAUSED BY THE HEAT AND DROUGHT IN 2003  Popular
Description:

Future climate warming is expected to enhance plant growth in temperate ecosystems and to increase carbon sequestration. But although severe regional heatwaves may become more frequent in a changing climate, and their impact on terrestrial carbon cycling is unclear. Europe experienced a particularly extreme climate anomaly during 2003, with July temperatures up to 6°C above long-term means, and annual precipitation deficits up to 300 mmy-1, that is 50% below the average. We used the 2003 heatwave as a ‘laboratory assistant’ to estimate the impact on terrestrial carbon cycling.


Author's Names: Ph. Ciais, M. Reichstein, N. Viovy, A. Granier, et al
Filesize: 23.98 Kb
Added on: 28-Jul-2005 Downloads: 180
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  SIMULATION OF THE RESPONSE OF NORTHEAST SIBERIA PERMAFROST CARBON STOCK TO THE GLOBAL WARMING 
Description:

The Siberian permafrost carbon stock has been studied using a newly developed soil model, which takes into account soil freezing/thawing and organic matter decomposition in the form of soil respiration and methanogenesis. The results show that the soil response to a rapid external warming can be a self-sustaining process involving permafrost melting, deep-soil respiration with associated heat generation, and methanogenesis. Most of the soil carbon is thus consumed until there is not enough of it to feed intense respiration and/or methanogenesis. This behavior is manifested only at sufficiently warm climate established after the warming. Carbon consumption in the extremely carbon-rich Yedoma Ice Complex region appears to be moderate due to cold climatic conditions.


Author's Names: D.V. Khvorostyanov, G. Krinner, P. Ciais, et al
Filesize: 64.11 Kb
Added on: 28-Jul-2005 Downloads: 38
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  MAN-INDUCED CHANGES IN C STORAGE DURING THE 20TH CENTURY: ENVIRONMENTAL AND GEOCHEMICAL RECORD 
Description:

Despite their relative small extension, wetlands are important as sources or sinks of C. But, due to their intermediate position between land and permanent water, they have been modified in the name of “health” or “productivity.” Such changes have altered substantially their ability to store/produce C greenhouse gasses but the main point is to establish until which point this changes are “structural” (implying the intrinsic environmental mechanisms), and therefore unrecoverable, or “casual” (implying not the environment processes but its “external”–not directly implied in the C storage/emission- components), and consequently recoverable. Temperate wetlands are strongly dependant on water availability due to their position but, on the other hand, use to be occupied by resistant species able to survive hard conditions. The example shown below presents a case of intense human activity on a Mediterranean wetland that has caused very intense changes in the flooded area but not so evident and perdurable in the main ecological relations implied in the C cycle.


Author's Names: F. Dominguez-Castro, J.I. Santisteban, R. Mediavilla, et al
Filesize: 48.81 Kb
Added on: 28-Jul-2005 Downloads: 35
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  CARBON-CLIMATE SYSTEM FEEDBACKS TO NATURAL AND ANTHROPOGENIC CLIMATE CHANGE 
Description:

A new three-dimensional global coupled carbon-climate model is presented in the framework of the Community Climate System Model (CSM-1.4). A 1000-year control simulation has stable global annual mean surface temperature and atmospheric CO2 with no flux adjustment in either physics or biogeochemistry. At low frequencies (timescale > 20 years), the ocean tends to damp (20-25%) slow, natural variations in atmospheric CO2 generated by the terrestrial biosphere. Transient experiments (1820-2100) show that carbon sink strengths are inversely related to the rate of fossil fuel emissions, so that carbon storage capacities of the land and oceans decrease and climate warming accelerates with faster CO2 emissions. There is a positive feedback between the carbon and climate systems, so that climate warming acts to increase the airborne fraction of anthropogenic CO2 and amplify the climate change itself. Globally, the amplification is small at the end of the 21st century in our model because of its low transient climate response and the near-cancellation between large regional changes in the hydrologic and ecosystem responses.


Author's Names: S.C. Doney. K. Lindsay, I. Fung, and J. John
Filesize: 71.56 Kb
Added on: 28-Jul-2005 Downloads: 47
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     Talk History
Friday, September 30
· Discussion Panel
· Nitrogen Regulation of Carbon Sequestration in Terrestrial Ecosystems in Respons
· The Role of Water Relations in Driving Grassland Ecosystem Responses to Rising A
· Unraveling the Decline in High-latitude Surface Ocean Carbonate
Thursday, September 29
· Hazards of Temperature on Food Availability in Changing Environments (HOT-FACE)
· The Amazon and the Modern Carbon Cycle
· New Coupled Climate-carbon Simulations from the IPSL Model
· The Changing Carbon Cycle
· What are the Most Important Factors for Climate-carbon Cycle Coupling?
· CO2 Uptake of the Marine Biosphere
· European-wide Reduction in Primary Productivity Caused by the Heat and Drought i
· Persistence of Nitrogen Limitation over Terrestrial Carbon Uptake
· Atmospheric CO2, Carbon Isotopes, the Sun, and Climate Change over the Last Mill
· Proposing a Mechanistic Understanding of Atmospheric CO2 During the late Pleist
· Greenhouse Gas (CO2, CH4) and Climate Evolution since 650 kyrs Deduced from Anta
Wednesday, September 28
· (In and) Out of Africa: Estimating the Carbon Exchange of a Continent
· Recent Shifts in Soil Dynamics on Growing Season Length, Productivity, and...
· Interannual Variability in the Carbon Exchange Using an Ecosystem-fire Model
· Photosynthesis and Respiration in Forests in Response to Environmental Changes
· Seasonal and Interannual Variability in Net Ecosystem CO2 Exchange in Japan
· Estimating Landscape-level Carbon Fluxes from Tower CO2 Mixing Ratio Measurement
· Monitoring Effects in Climate and Fire Regime on Net Ecosystem Production
· Radiative Forcing from a Boreal Forest Fire
· The Influence of Soil and Water Management on Carbon Erosion and Burial
· Spatial and Temporal Patterns of CO2, CH4, and N2O Fluxes in Ecosystems
· Modeling the History of Terrestrial Carbon Sources and Sinks
· The Age of Carbon Respired from Terrestrial Ecosystems
· Discussion Panel
· The Underpinnings of Land Use History
Tuesday, September 27
· Regional CO2 Fluxes for North America Estimated from NOAA/CMDL Observatories

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The 7th International CO2 Conference

The Omni Interlocken Resort
September 25th - 30th
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