A lower limit to atmospheric CO2 concentrations over the past 800,000 years

2017 ◽  
Vol 10 (4) ◽  
pp. 295-298 ◽  
Author(s):  
E. D. Galbraith ◽  
S. Eggleston
Keyword(s):  
Lower Limit ◽  
Atmospheric Co2 ◽  
The Past ◽  
Co2 Concentrations ◽  
Atmospheric Co2 Concentrations

Homeostatic response of Aptian gymnosperms to changes in atmospheric CO2 concentrations

Geology ◽  
2021 ◽  
Author(s):  
Germán Mora ◽  
Ana M. Carmo ◽  
William Elliott
Keyword(s):  
Stomatal Closure ◽  
Carbon Assimilation ◽  
Atmospheric Co2 ◽  
The Past ◽  
A Value ◽  
Co2 Concentrations ◽  
Bulk Organic Matter ◽  
The Subject ◽  
Atmospheric Co2 Concentrations ◽  
Homeostatic Response

The sensitivity of plant carbon isotope fractionation (13Δleaf) to changes in atmospheric CO2 concentrations (Ca) is the subject of heavy debate, with some studies finding no sensitivity, while others show a strong dependency. We tested the hypothesis of photosynthetic homeostasis by using δ13C of n-alkanes, cuticles, and bulk organic matter of gymnosperm-rich rocks (Arundel Clay) from two sites deposited during the Aptian, a time that experienced significant Ca variations. Our results show no effect of Ca on 13Δleaf, and a relatively constant Ci/Ca (0.64 ± 0.04, 1σ; i—intercellular space), a value that is similar to that of modern gymnosperms. These results suggest that Aptian gymnosperms used homeostatic adjustments with rising Ca, probably involving increased carbon assimilation and/or stomatal closure, a response also found in modern gymnosperms. The similarity between Aptian and modern gymnosperms suggests that the processes responsible for regulating CO2 and water vapor exchange during photosynthesis have remained unaltered in gymnosperms for the past 128 m.y.

scholarly journals The ocean carbon sink – impacts, vulnerabilities, and challenges

2014 ◽  
Vol 5 (2) ◽  
pp. 1607-1672
Author(s):  
C. Heinze ◽  
S. Meyer ◽  
N. Goris ◽  
L. Anderson ◽  
R. Steinfeldt ◽  
...  
Keyword(s):  
Carbon Sink ◽  
Mitigation Strategies ◽  
Atmospheric Co2 ◽  
Co2 Uptake ◽  
Spatial And Temporal Scales ◽  
The Past ◽  
Research Fields ◽  
Co2 Concentrations ◽  
Ocean Carbon ◽  
Atmospheric Co2 Concentrations

Abstract. Carbon dioxide (CO2) is, next to water vapour, considered to be the most important natural greenhouse gas on Earth. Rapidly rising atmospheric CO2 concentrations caused by human actions such as fossil-fuel burning, land-use change or cement production over the past 250 years have given cause for concern that changes in Earth's climate system may progress at a much faster pace and larger extent than during the past 20 000 years. Investigating global carbon cycle pathways and finding suitable mitigation strategies has, therefore, become of major concern in many research fields. The oceans have a key role in regulating atmospheric CO2 concentrations and currently take up about 25% of annual anthropogenic carbon emissions to the atmosphere. Questions that yet need to be answered are what the carbon uptake kinetics of the oceans will be in the future and how the increase in oceanic carbon load will affect its ecosystems and their services. This requires comprehensive investigations, including high-quality ocean carbon measurements on different spatial and temporal scales, the management of data in sophisticated data bases, the application of state-of-the-art Earth system models to provide future projections for given emission scenarios as well as a global synthesis and outreach to policy makers. In this paper, the current understanding of the ocean as an important carbon sink is reviewed with respect to these topics. Emphasis is placed on the complex interplay of different physical, chemical, and biological processes that yield both positive and negative air–sea flux values for natural and anthropogenic CO2 as well as on increased CO2 (uptake) as the regulating force of the radiative warming of the atmosphere and the gradual acidification of the oceans. Major future ocean carbon challenges in the fields of ocean observations, modelling, and process research as well as the relevance of other biogeochemical cycles and greenhouse gases are discussed.

scholarly journals The ocean carbon sink – impacts, vulnerabilities and challenges

2015 ◽  
Vol 6 (1) ◽  
pp. 327-358 ◽  
Author(s):  
C. Heinze ◽  
S. Meyer ◽  
N. Goris ◽  
L. Anderson ◽  
R. Steinfeldt ◽  
...  
Keyword(s):  
Carbon Sink ◽  
Mitigation Strategies ◽  
Atmospheric Co2 ◽  
Co2 Uptake ◽  
Spatial And Temporal Scales ◽  
The Past ◽  
Research Fields ◽  
Co2 Concentrations ◽  
Ocean Carbon ◽  
Atmospheric Co2 Concentrations

Abstract. Carbon dioxide (CO2) is, next to water vapour, considered to be the most important natural greenhouse gas on Earth. Rapidly rising atmospheric CO2 concentrations caused by human actions such as fossil fuel burning, land-use change or cement production over the past 250 years have given cause for concern that changes in Earth's climate system may progress at a much faster pace and larger extent than during the past 20 000 years. Investigating global carbon cycle pathways and finding suitable adaptation and mitigation strategies has, therefore, become of major concern in many research fields. The oceans have a key role in regulating atmospheric CO2 concentrations and currently take up about 25% of annual anthropogenic carbon emissions to the atmosphere. Questions that yet need to be answered are what the carbon uptake kinetics of the oceans will be in the future and how the increase in oceanic carbon inventory will affect its ecosystems and their services. This requires comprehensive investigations, including high-quality ocean carbon measurements on different spatial and temporal scales, the management of data in sophisticated databases, the application of Earth system models to provide future projections for given emission scenarios as well as a global synthesis and outreach to policy makers. In this paper, the current understanding of the ocean as an important carbon sink is reviewed with respect to these topics. Emphasis is placed on the complex interplay of different physical, chemical and biological processes that yield both positive and negative air–sea flux values for natural and anthropogenic CO2 as well as on increased CO2 (uptake) as the regulating force of the radiative warming of the atmosphere and the gradual acidification of the oceans. Major future ocean carbon challenges in the fields of ocean observations, modelling and process research as well as the relevance of other biogeochemical cycles and greenhouse gases are discussed.

Mineral composition of durum wheat grain and pasta under increasing atmospheric CO2 concentrations

2018 ◽  
Vol 242 ◽  
pp. 53-61 ◽  
Author(s):  
Romina Beleggia ◽  
Mariagiovanna Fragasso ◽  
Franco Miglietta ◽  
Luigi Cattivelli ◽  
Valeria Menga ◽  
...  
Keyword(s):  
Durum Wheat ◽  
Mineral Composition ◽  
Atmospheric Co2 ◽  
Wheat Grain ◽  
Co2 Concentrations ◽  
Atmospheric Co2 Concentrations
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