Climate Response at the Paleocene–Eocene Thermal Maximum to Greenhouse Gas Forcing—A Model Study with CCSM3

2010 ◽  
Vol 23 (10) ◽  
pp. 2562-2584 ◽  
Author(s):  
A. Winguth ◽  
C. Shellito ◽  
C. Shields ◽  
C. Winguth
Keyword(s):  
Climate Change ◽  
Surface Temperature ◽  
Greenhouse Gas ◽  
Methane Hydrate ◽  
Atmospheric Co2 ◽  
Future Climate Change ◽  
High Latitudes ◽  
Co2 Concentrations ◽  
Thermal Maximum ◽  
Atmospheric Co2 Concentrations

Abstract The Paleocene–Eocene Thermal Maximum (PETM; 55 Ma) is of particular interest since it is regarded as a suitable analog to future climate change. In this study, the PETM climate is investigated using the Community Climate System Model (CCSM3) with atmospheric CO2 concentrations of 4×, 8×, and 16× the preindustrial value. Simulated climate change from 4× to 8× atmospheric CO2 concentration, possibly corresponding to an environmental precursor of the PETM event, leads to a warming of the North Atlantic Ocean Intermediate-Water masses, thus lowering the critical depth for methane hydrate destabilization by ∼500 m. A further increase from 8× to 16×CO2, analogous to a possible massive methane hydrate release, results in global oceanic warming and stratification. The increase in the radiative surface warming, especially at high latitudes, is partially offset by a decrease in the ocean heat transport due to a reduced overturning circulation. Surface temperature values simulated in the 16×CO2 PETM run represent the closest match to surface temperature reconstructions from proxies for this period. Simulated PETM precipitation, characterized by a slight northward shift of the intertropical convergence zone, increases at higher CO2 concentrations, especially for the northern midlatitudes as well as the high latitudes in both hemispheres. Data-inferred precipitation values and gradients for North America and Spain, for instance, are in good agreement with the 16×CO2 simulation. Increasing atmospheric CO2 concentrations might also have favored the release of terrestrial methane through warmer and wetter conditions over land, thus reinforcing the greenhouse gas concentration increase.

scholarly journals Agricultural Greenhouse Gas Emissions in a Data-Scarce Region Using a Scenario-Based Modeling Approach: A Case Study in Southeastern USA

Agronomy ◽  
2021 ◽  
Vol 11 (7) ◽  
pp. 1323
Author(s):  
Mahnaz Afroz ◽  
Runwei Li ◽  
Gang Chen ◽  
Aavudai Anandhi
Keyword(s):  
Climate Change ◽  
Greenhouse Gas Emissions ◽  
Greenhouse Gas ◽  
Atmospheric Co2 ◽  
Similar Data ◽  
Validation Data ◽  
Gas Emissions ◽  
Southeastern Usa ◽  
Co2 Concentrations ◽  
Atmospheric Co2 Concentrations

Climate change may impact agricultural greenhouse gas emissions (GHGs) and yields under higher temperatures, higher atmospheric CO2 concentrations, and variable precipitations. This calls for adaptation strategies to optimize agricultural productions with minimal GHGs. This study aimed to identify these optimum agricultural managements in response to current and projected climatic scenarios for the Choctawhatchee Basin in Southeastern USA, an experimentally unexplored data-scarce region lacking validation data. This scenario-based modeling study analyzed a total of 1344 scenarios consisting of four major crops, eight managements (varying tillage, manuring, and residue), and forty climatic combinations under current as wells as two representative concentration pathways with process-based Denitrification and Decomposition (DNDC) model. The results indicated that the region’s GHGs and yields were most affected by higher temperatures (≥+3 °C) and extreme precipitation changes (≥±40%), while high atmospheric CO2 concentrations exerted positive fertilization effects. The manure-related and higher residue incorporation scenarios were found to be better options in varying climates with minimal present global warming potentials (GWP) of 0.23 k to −29.1 k MT equivalent CO2. As such, the study presented climate change impacts and potential mitigation options in the study region while presenting a framework to design GHG mitigation in similar data-scarce regions.

scholarly journals Historical and future contributions of inland waters to the Congo basin carbon balance

2020 ◽  
Author(s):  
Adam Hastie ◽  
Ronny Lauerwald ◽  
Philippe Ciais ◽  
Fabrice Papa ◽  
Pierre Regnier
Keyword(s):  
Climate Change ◽  
Organic Carbon ◽  
Significant Proportion ◽  
Congo Basin ◽  
Atmospheric Co2 ◽  
Future Climate Change ◽  
Inland Waters ◽  
Co2 Concentrations ◽  
C Cycle ◽  
Atmospheric Co2 Concentrations

Abstract. As the second largest area of contiguous tropical rainforest and second largest river basin in the world, the Congo basin has a significant role to play in the global carbon (C) cycle. Inventories suggest that terrestrial net primary productivity (NPP) and C storage in tree biomass has increased in recent decades in intact forests of tropical Africa, due in large part to a combination of increasing atmospheric CO2 concentrations and climate change, while rotational agriculture and logging have caused C losses. For the present day, it has been shown that a significant proportion of global terrestrial NPP is transferred laterally to the land-ocean aquatic continuum (LOAC) as dissolved CO2, dissolved organic carbon (DOC) and particulate organic carbon (POC). Whilst the importance of LOAC fluxes in the Congo basin has been demonstrated for the present day, it is not known to what extent these fluxes have been perturbed historically, how they are likely to change under future climate change and land use scenarios, and in turn what impact these changes might have on the overall C cycle of the basin. Here we apply the ORCHILEAK model to the Congo basin and show that 4% of terrestrial NPP (NPP = 5,800 ± 166 Tg C yr−1) is currently exported from soils to inland waters. Further, we found that aquatic C fluxes have undergone considerable perturbation since 1861 to the present day, with aquatic CO2 evasion and C export to the coast increasing by 26 % (186 ± 41 Tg C yr−1 to 235 ± 54 Tg C yr−1) and 25 % (12 ± 3 Tg C yr−1 to 15 ± 4 Tg C yr−1) respectively, largely because of rising atmospheric CO2 concentrations. Moreover, under climate scenario RCP 6.0 we predict that this perturbation will continue; over the full simulation period (1861–2099), we estimate that aquatic CO2 evasion and C export to the coast will increase by 79 % and 67 % respectively. Finally, we show that the proportion of terrestrial NPP lost to the LOAC also increases from approximately 3 % to 5 % from 1861–2099 as a result of increasing atmospheric CO2 concentrations and climate change.

scholarly journals Historical and future contributions of inland waters to the Congo Basin carbon balance

2021 ◽  
Vol 12 (1) ◽  
pp. 37-62
Author(s):  
Adam Hastie ◽  
Ronny Lauerwald ◽  
Philippe Ciais ◽  
Fabrice Papa ◽  
Pierre Regnier
Keyword(s):  
Climate Change ◽  
Organic Carbon ◽  
Congo Basin ◽  
Atmospheric Co2 ◽  
Future Climate Change ◽  
Inland Waters ◽  
Future Projections ◽  
Co2 Concentrations ◽  
C Cycle ◽  
Atmospheric Co2 Concentrations

Abstract. As the second largest area of contiguous tropical rainforest and second largest river basin in the world, the Congo Basin has a significant role to play in the global carbon (C) cycle. For the present day, it has been shown that a significant proportion of global terrestrial net primary productivity (NPP) is transferred laterally to the land–ocean aquatic continuum (LOAC) as dissolved CO2, dissolved organic carbon (DOC), and particulate organic carbon (POC). Whilst the importance of LOAC fluxes in the Congo Basin has been demonstrated for the present day, it is not known to what extent these fluxes have been perturbed historically, how they are likely to change under future climate change and land use scenarios, and in turn what impact these changes might have on the overall C cycle of the basin. Here we apply the ORCHILEAK model to the Congo Basin and estimate that 4 % of terrestrial NPP (NPP = 5800±166 Tg C yr−1) is currently exported from soils and vegetation to inland waters. Further, our results suggest that aquatic C fluxes may have undergone considerable perturbation since 1861 to the present day, with aquatic CO2 evasion and C export to the coast increasing by 26 % (186±41 to 235±54 Tg C yr−1) and 25 % (12±3 to 15±4 Tg C yr−1), respectively, largely because of rising atmospheric CO2 concentrations. Moreover, under climate scenario RCP6.0 we predict that this perturbation could continue; over the full simulation period (1861–2099), we estimate that aquatic CO2 evasion and C export to the coast could increase by 79 % and 67 %, respectively. Finally, we show that the proportion of terrestrial NPP lost to the LOAC could increase from approximately 3 % to 5 % from 1861–2099 as a result of increasing atmospheric CO2 concentrations and climate change. However, our future projections of the Congo Basin C fluxes in particular need to be interpreted with some caution due to model limitations. We discuss these limitations, including the wider challenges associated with applying the current generation of land surface models which ignore nutrient dynamics to make future projections of the tropical C cycle, along with potential next steps.

scholarly journals Heterogeneous CO<sub>2</sub> and CH<sub>4</sub> content of glacial meltwater from the Greenland Ice Sheet and implications for subglacial carbon processes

2021 ◽  
Vol 15 (3) ◽  
pp. 1627-1644
Author(s):  
Andrea J. Pain ◽  
Jonathan B. Martin ◽  
Ellen E. Martin ◽  
Åsa K. Rennermalm ◽  
Shaily Rahman
Keyword(s):  
Greenhouse Gas ◽  
Ice Sheet ◽  
Greenland Ice Sheet ◽  
Mineral Weathering ◽  
Atmospheric Co2 ◽  
The Arctic ◽  
Co2 Concentrations ◽  
Geochemical Models ◽  
Atmospheric Co2 Concentrations ◽  
The Impact

Abstract. Accelerated melting of the Greenland Ice Sheet has increased freshwater delivery to the Arctic Ocean and amplified the need to understand the impact of Greenland Ice Sheet meltwater on Arctic greenhouse gas budgets. We evaluate subglacial discharge from the Greenland Ice Sheet for carbon dioxide (CO2) and methane (CH4) concentrations and δ13C values and use geochemical models to evaluate subglacial CH4 and CO2 sources and sinks. We compare discharge from southwest (a sub-catchment of the Isunnguata Glacier, sub-Isunnguata, and the Russell Glacier) and southern Greenland (Kiattut Sermiat). Meltwater CH4 concentrations vary by orders of magnitude between sites and are saturated with respect to atmospheric concentrations at Kiattut Sermiat. In contrast, meltwaters from southwest sites are supersaturated, even though oxidation reduces CH4 concentrations by up to 50 % during periods of low discharge. CO2 concentrations range from supersaturated at sub-Isunnguata to undersaturated at Kiattut Sermiat. CO2 is consumed by mineral weathering throughout the melt season at all sites; however, differences in the magnitude of subglacial CO2 sources result in meltwaters that are either sources or sinks of atmospheric CO2. At the sub-Isunnguata site, the predominant source of CO2 is organic matter (OM) remineralization. However, multiple or heterogeneous subglacial CO2 sources maintain atmospheric CO2 concentrations at Russell but not at Kiattut Sermiat, where CO2 is undersaturated. These results highlight a previously unrecognized degree of heterogeneity in greenhouse gas dynamics under the Greenland Ice Sheet. Future work should constrain the extent and controls of heterogeneity to improve our understanding of the impact of Greenland Ice Sheet melt on Arctic greenhouse gas budgets, as well as the role of continental ice sheets in greenhouse gas variations over glacial–interglacial timescales.

Sources and Sinks of Atmospheric CO2

1992 ◽  
Vol 40 (5) ◽  
pp. 407 ◽  
Author(s):  
JA Taylor ◽  
J Lloyd
Keyword(s):  
Climate Change ◽  
Biomass Burning ◽  
Transport Model ◽  
Atmospheric Co2 ◽  
Tropical Rainforests ◽  
Co2 Uptake ◽  
Tracer Transport ◽  
Intergovernmental Panel ◽  
Co2 Concentrations ◽  
Atmospheric Co2 Concentrations

The biosphere plays an important role in determining the sources, sinks, levels and rates of change of atmospheric CO2 concentrations. Significant uncertainties remain in estimates of the fluxes of CO2 from biomass burning and deforestation, and uptake and storage of CO2 by the biosphere arising from increased atmospheric CO2 concentrations. Calculation of probable rates of carbon sequestration for the major ecosystem complexes and global 3-D tracer transport model runs indicate the possibility that a significant net CO2 uptake (> 1 Pg C yr-1), a CO2 'fertilisation effect', may be occurring in tropical rainforests, effectively accounting for much of the 'missing sink'. This sink may currently balance much of the CO2 added to the atmosphere from deforestation and biomass burning. Interestingly, CO2 released from biomass burning may itself be playing an important role in enhanced carbon storage by tropical rainforests. This has important implications for predicting future CO2 concentrations. If tropical rainforest destruction continues then much of the CO2 stored as a result of the CO2 'fertilisation effect' will be rereleased to the atmosphere and much of the 'missing sink' will disappear. These effects have not been considered in the IPCC (Intergovernmental Panel on Climate Change) projections of future atmospheric CO2 concentrations. Predictions which take account of the combined effects of deforestation, the return of carbon previously stored through the CO2 'fertilisation effect' and the loss of a large proportion of the 'missing sink' as a result of deforestation, would result in much higher predicted concentrations and rates of increase of atmospheric CO2 and, as a consequence, accelerated rates of climate change.

scholarly journals Global mean surface temperature and climate sensitivity of the early Eocene Climatic Optimum (EECO), Paleocene–Eocene Thermal Maximum (PETM), and latest Paleocene

2020 ◽  
Vol 16 (5) ◽  
pp. 1953-1968 ◽  
Author(s):  
Gordon N. Inglis ◽  
Fran Bragg ◽  
Natalie J. Burls ◽  
Margot J. Cramwinckel ◽  
David Evans ◽  
...  
Keyword(s):  
Climate Change ◽  
Surface Temperature ◽  
Climate Sensitivity ◽  
Future Climate Change ◽  
Early Eocene ◽  
Early Eocene Climatic Optimum ◽  
Thermal Maximum ◽  
Global Mean Surface Temperature ◽  
Climatic Optimum ◽  
Global Mean

Abstract. Accurate estimates of past global mean surface temperature (GMST) help to contextualise future climate change and are required to estimate the sensitivity of the climate system to CO2 forcing through Earth's history. Previous GMST estimates for the latest Paleocene and early Eocene (∼57 to 48 million years ago) span a wide range (∼9 to 23 ∘C higher than pre-industrial) and prevent an accurate assessment of climate sensitivity during this extreme greenhouse climate interval. Using the most recent data compilations, we employ a multi-method experimental framework to calculate GMST during the three DeepMIP target intervals: (1) the latest Paleocene (∼57 Ma), (2) the Paleocene–Eocene Thermal Maximum (PETM; 56 Ma), and (3) the early Eocene Climatic Optimum (EECO; 53.3 to 49.1 Ma). Using six different methodologies, we find that the average GMST estimate (66 % confidence) during the latest Paleocene, PETM, and EECO was 26.3 ∘C (22.3 to 28.3 ∘C), 31.6 ∘C (27.2 to 34.5 ∘C), and 27.0 ∘C (23.2 to 29.7 ∘C), respectively. GMST estimates from the EECO are ∼10 to 16 ∘C warmer than pre-industrial, higher than the estimate given by the Intergovernmental Panel on Climate Change (IPCC) 5th Assessment Report (9 to 14 ∘C higher than pre-industrial). Leveraging the large “signal” associated with these extreme warm climates, we combine estimates of GMST and CO2 from the latest Paleocene, PETM, and EECO to calculate gross estimates of the average climate sensitivity between the early Paleogene and today. We demonstrate that “bulk” equilibrium climate sensitivity (ECS; 66 % confidence) during the latest Paleocene, PETM, and EECO is 4.5 ∘C (2.4 to 6.8 ∘C), 3.6 ∘C (2.3 to 4.7 ∘C), and 3.1 ∘C (1.8 to 4.4 ∘C) per doubling of CO2. These values are generally similar to those assessed by the IPCC (1.5 to 4.5 ∘C per doubling CO2) but appear incompatible with low ECS values (<1.5 per doubling CO2).

An intensification of atmospheric CO2 concentrations due to the surface temperature extremes in India

2021 ◽  
Vol 133 (6) ◽  
pp. 1647-1659
Author(s):  
Smrati Gupta ◽  
Yogesh K. Tiwari ◽  
J. V. Revadekar ◽  
Pramit Kumar Deb Burman ◽  
Supriyo Chakraborty ◽  
...  
Keyword(s):  
Surface Temperature ◽  
Atmospheric Co2 ◽  
Temperature Extremes ◽  
Co2 Concentrations ◽  
Atmospheric Co2 Concentrations

scholarly journals El Niño-like climate change in a model with increased atmospheric CO2 concentrations

Nature ◽  
1996 ◽  
Vol 382 (6586) ◽  
pp. 56-60 ◽  
Author(s):  
Gerald A. Meehl ◽  
Warren M. Washington
Keyword(s):  
Climate Change ◽  
El Niño ◽  
El Nino ◽  
Atmospheric Co2 ◽  
Co2 Concentrations ◽  
Atmospheric Co2 Concentrations

scholarly journals No way out? The double-bind in seeking global prosperity along with mitigated climate change

2011 ◽  
Vol 2 (1) ◽  
pp. 315-354 ◽  
Author(s):  
T. J. Garrett
Keyword(s):  
Climate Change ◽  
Energy Consumption ◽  
Atmospheric Co2 ◽  
Double Bind ◽  
Greenhouse Warming ◽  
Emission Rates ◽  
Co2 Concentrations ◽  
Co2 Levels ◽  
Atmospheric Co2 Concentrations ◽  
Ipcc Sres

Abstract. In a prior study (Garrett, 2011), I introduced a simple thermodynamics-based economic growth model. By treating civilization as a whole, it was found that the global economy's current rate of energy consumption can be tied through a constant to its current accumulation of wealth. The value of the constant is λ = 9.7 ± 0.3 milliwatts per 1990 US dollar. Here, this model is coupled to a linear formulation for the evolution of atmospheric CO2 concentrations. Despite the model's extreme simplicity, multi-decadal hindcasts of trajectories in gross world product (GWP) and CO2 agree closely with recent observations. Extending the model to the future, the model implies that the well-known IPCC SRES scenarios substantially underestimate how much CO2 levels will rise for a given level of future economic prosperity. Instead, what is shown is that, like a long-term natural disaster, future greenhouse warming should be expected to retard the real growth of wealth through inflationary pressures. Because wealth is tied to rates of energy consumption through the constant λ, it follows that dangerous climate change should be a negative feedback on CO2 emission rates, and therefore the ultimate extent of greenhouse warming. Nonetheless, if atmospheric CO2 concentrations are to remain below a "dangerous" level of 450 ppmv (Hansen et al., 2007), there will have to be some combination of an unrealistically rapid rate of energy decarbonization and a near immediate collapse of civilization wealth. Effectively, civilization is in a double-bind. If civilization does not collapse quickly this century, then CO2 levels will likely end up exceeding 1000 ppmv; but, if CO2 levels rise by this much, then the danger is that civilization will gradually tend towards collapse.

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