On the multi-century Southern Hemisphere response to changes in atmospheric CO2-concentration in a Global Climate Model

2005 ◽  
Vol 89 (1-4) ◽  
pp. 17-36 ◽  
Author(s):  
M. L. Bates ◽  
M. H. England ◽  
W. P. Sijp
Keyword(s):  
Southern Hemisphere ◽  
Climate Model ◽  
Global Climate ◽  
Global Climate Model ◽  
Co2 Concentration ◽  
Atmospheric Co2 ◽  
Atmospheric Co2 Concentration

scholarly journals Investigating the evolution of major Northern Hemisphere ice sheets during the last glacial-interglacial cycle

2009 ◽  
Vol 5 (3) ◽  
pp. 329-345 ◽  
Author(s):  
S. Bonelli ◽  
S. Charbit ◽  
M. Kageyama ◽  
M.-N. Woillez ◽  
G. Ramstein ◽  
...  
Keyword(s):  
Northern Hemisphere ◽  
Climate Model ◽  
Ice Sheets ◽  
Ice Sheet ◽  
Co2 Concentration ◽  
Atmospheric Co2 ◽  
Glacial Cycle ◽  
Last Glacial ◽  
Atmospheric Co2 Concentration ◽  
The Last Glacial

Abstract. A 2.5-dimensional climate model of intermediate complexity, CLIMBER-2, fully coupled with the GREMLINS 3-D thermo-mechanical ice sheet model is used to simulate the evolution of major Northern Hemisphere ice sheets during the last glacial-interglacial cycle and to investigate the ice sheets responses to both insolation and atmospheric CO2 concentration. This model reproduces the main phases of advance and retreat of Northern Hemisphere ice sheets during the last glacial cycle, although the amplitude of these variations is less pronounced than those based on sea level reconstructions. At the last glacial maximum, the simulated ice volume is 52.5×1015 m3 and the spatial distribution of both the American and Eurasian ice complexes is in reasonable agreement with observations, with the exception of the marine parts of these former ice sheets. A set of sensitivity studies has also been performed to assess the sensitivity of the Northern Hemisphere ice sheets to both insolation and atmospheric CO2. Our results suggest that the decrease of summer insolation is the main factor responsible for the early build up of the North American ice sheet around 120 kyr BP, in agreement with benthic foraminifera δ18O signals. In contrast, low insolation and low atmospheric CO2 concentration are both necessary to trigger a long-lasting glaciation over Eurasia.

scholarly journals Black Carbon Increases Frequency of Extreme ENSO Events

2019 ◽  
Vol 32 (23) ◽  
pp. 8323-8333 ◽  
Author(s):  
Sijia Lou ◽  
Yang Yang ◽  
Hailong Wang ◽  
Jian Lu ◽  
Steven J. Smith ◽  
...  
Keyword(s):  
Black Carbon ◽  
Climate Models ◽  
Climate Model ◽  
Southern Oscillation ◽  
Global Climate ◽  
Global Climate Model ◽  
Co2 Concentration ◽  
Enso Events ◽  
Aerosol Forcing ◽  
Earth’S Climate

ABSTRACT El Niño–Southern Oscillation (ENSO) is the leading mode of Earth’s climate variability at interannual time scales with profound ecological and societal impacts, and it is projected to intensify in many climate models as the climate warms under the forcing of increasing CO2 concentration. Since the preindustrial era, black carbon (BC) emissions have substantially increased in the Northern Hemisphere. But how BC aerosol forcing may influence the occurrence of the extreme ENSO events has rarely been investigated. In this study, using simulations of a global climate model, we show that increases in BC emissions from both the midlatitudes and Arctic weaken latitudinal temperature gradients and northward heat transport, decrease tropical energy divergence, and increase sea surface temperature over the tropical oceans, with a surprising consequential increase in the frequency of extreme ENSO events. A corollary of this study is that reducing BC emissions might serve to mitigate the possible increasing frequency of extreme ENSO events under greenhouse warming, if the modeling result can be translated into the climate in reality.

Responses of woody Cerrado species to rising atmospheric CO2 concentration and water stress: gains and losses

2016 ◽  
Vol 43 (12) ◽  
pp. 1183 ◽  
Author(s):  
João Paulo Souza ◽  
Nayara M. J. Melo ◽  
Eduardo G. Pereira ◽  
Alessandro D. Halfeld ◽  
Ingrid N. Gomes ◽  
...  
Keyword(s):  
Water Stress ◽  
Elevated Co2 ◽  
Global Climate ◽  
Net Photosynthesis ◽  
Co2 Concentration ◽  
Atmospheric Co2 ◽  
Ecosystem Functions ◽  
Total Biomass ◽  
High Co2 ◽  
Atmospheric Co2 Concentration

The rise in atmospheric CO2 concentration ([CO2]) has been accompanied by changes in other environmental factors of global climate change, such as drought. Tracking the early growth of plants under changing conditions can determine their ecophysiological adjustments and the consequences for ecosystem functions. This study investigated long-term ecophysiological responses in three woody Cerrado species: Hymenaea stigonocarpa Mart. ex Hayne, Solanum lycocarpum A. St.-Hil. and Tabebuia aurea (Silva Manso) Benth. and Hook. f. ex S. Moore, grown under ambient and elevated [CO2]. Plants were grown for 515 days at ambient (430 mg dm–3) or elevated [CO2] (700 mg dm–3). Some plants were also subjected to water stress to investigate the synergy between atmospheric [CO2] and soil water availability, and its effect on plant growth. All three species showed an increase in maximum net photosynthesis (PN) and chlorophyll index under high [CO2]. Transpiration decreased in some species under high [CO2] despite daily watering and a corresponding increase in water use efficiency was observed. Plants grown under elevated [CO2] and watered daily had greater leaf area and total biomass production than plants under water stress and ambient [CO2]. The high chlorophyll and PN in cerrado plants grown under elevated [CO2] are an investment in light use and capture and higher Rubisco carboxylation rate, respectively. The elevated [CO2] had a positive influence on biomass accumulation in the cerrado species we studied, as predicted for plants under high [CO2]. So, even with water stress, Cerrado species under elevated [CO2] had better growth.

scholarly journals The CO<sub>2</sub> inhibition of terrestrial isoprene emission significantly affects future ozone projections

2008 ◽  
Vol 8 (6) ◽  
pp. 19891-19916 ◽  
Author(s):  
P. J. Young ◽  
A. Arneth ◽  
G. Schurgers ◽  
G. Zeng ◽  
J. A. Pyle
Keyword(s):  
Climate Model ◽  
Carbon Assimilation ◽  
Co2 Concentration ◽  
Atmospheric Co2 ◽  
Isoprene Emission ◽  
Atmospheric Co2 Concentration ◽  
Source Regions ◽  
Late 21St Century ◽  
Response To Temperature ◽  
The Impact

Abstract. Simulations of future tropospheric composition often include substantial increases in biogenic isoprene emissions arising from the Arrhenius-like leaf emission response and warmer surface temperatures, and from enhanced vegetation productivity in response to temperature and atmospheric CO2 concentration. However, a number of recent laboratory and field data have suggested a direct inhibition of leaf isoprene production by increasing atmospheric CO2 concentration, notwithstanding isoprene being produced from precursor molecules that include some of the primary products of carbon assimilation. The cellular mechanism that underlies the decoupling of leaf photosynthesis and isoprene production still awaits a full explanation but accounting for this observation in a dynamic vegetation model that contains a semi-mechanistic treatment of isoprene emissions has been shown to change future global isoprene emission estimates notably. Here we use these estimates in conjunction with a chemistry-climate model to compare the effects of isoprene simulations without and with a direct CO2-inhibition on late 21st century O3 and OH levels. The impact on surface O3 was significant. Including the CO2-inhibition of isoprene resulted in opposing responses in polluted (O3 decreases of up to 10 ppbv) vs. less polluted (O3 increases of up to 10 ppbv) source regions, due to isoprene nitrate and peroxy acetyl nitrate (PAN) chemistry. OH concentration increased with relatively lower future isoprene emissions, decreasing methane lifetime by ~7 months. Our simulations underline the large uncertainties in future chemistry and climate studies due to biogenic emission patterns and emphasize the problems of using globally averaged climate metrics to quantify the atmospheric impact of reactive, heterogeneously distributed substances.

scholarly journals EC-Earth3-AerChem, a global climate model with interactive aerosols and atmospheric chemistry participating in CMIP6

2020 ◽  
Author(s):  
Twan van Noije ◽  
Tommi Bergman ◽  
Philippe Le Sager ◽  
Declan O'Donnell ◽  
Risto Makkonen ◽  
...  
Keyword(s):  
20Th Century ◽  
Southern Hemisphere ◽  
Air Temperature ◽  
Atmospheric Chemistry ◽  
Climate Model ◽  
Global Climate ◽  
Global Climate Model ◽  
Surface Air Temperature ◽  
Model Intercomparison ◽  
Intercomparison Project

Abstract. This paper documents the global climate model EC-Earth3-AerChem, one of the members of the EC-Earth3 family of models participating in the Coupled Model Intercomparison Project phase 6 (CMIP6). EC-Earth3-AerChem has interactive aerosols and atmospheric chemistry and contributes to the Aerosols and Chemistry Model Intercomparison Project (AerChemMIP). In this paper, we give an overview of the model and describe in detail how it differs from the other EC-Earth3 configurations, and what the new features are compared to the previously documented version of the model (EC-Earth 2.4). We explain how the model was tuned and spun up under pre-industrial conditions and characterize the model's general performance on the basis of a selection of coupled simulations conducted for CMIP6. The mean energy imbalance at the top of the atmosphere in the pre-industrial control simulation is −0.10 ± 0.25 W m−2 and shows no significant drift. The corresponding mean global surface air temperature is 14.05 ± 0.16 °C, with a small drift of −0.075 ± 0.009 °C per century. The model's effective equilibrium climate sensitivity is estimated at 3.9 °C and its transient climate response at 2.1 °C. The CMIP6 historical simulation displays spurious interdecadal variability in Northern Hemisphere temperatures, resulting in a large spread among ensemble members and a tendency to underestimate observed annual surface temperature anomalies from the early 20th century onwards. The observed warming of the Southern Hemisphere is well reproduced by the model. Compared to the ERA5 reanalysis of the European Centre for Medium-Range Weather Forecasts, the ensemble mean surface air temperature climatology for 1995–2014 has an average bias of −0.86 ± 0.35 °C in the Northern Hemisphere and 1.29 ± 0.05 °C in the Southern Hemisphere. The Southern Hemisphere warm bias is largely caused by errors in shortwave cloud radiative effects over the Southern Ocean, a deficiency of many climate models. Changes in the emissions of near-term climate forcers (NTCFs) have significant climate effects from the 20th century onwards. For the SSP3-7.0 shared socio-economic pathway, the model gives a global warming at the end of the 21st century (2091–2100) of 4.9 °C above the pre-industrial mean. A 0.5 °C stronger warming is obtained for the AerChemMIP scenario with reduced emissions of NTCFs. With concurrent reductions of future methane concentrations, the warming is projected to be reduced by 0.5 °C.

scholarly journals The influence of vegetation dynamics on anthropogenic climate change

2012 ◽  
Vol 3 (2) ◽  
pp. 233-243 ◽  
Author(s):  
U. Port ◽  
V. Brovkin ◽  
M. Claussen
Keyword(s):  
Climate Change ◽  
Vegetation Cover ◽  
Vegetation Dynamics ◽  
Global Climate ◽  
Co2 Concentration ◽  
Atmospheric Co2 ◽  
Tree Cover ◽  
Earth System ◽  
Atmospheric Co2 Concentration ◽  
Global Mean

Abstract. In this study, vegetation–climate and vegetation–carbon cycle interactions during anthropogenic climate change are assessed by using the Earth System Model of the Max Planck Institute for Meteorology (MPI ESM) that includes vegetation dynamics and an interactive carbon cycle. We assume anthropogenic CO2 emissions according to the RCP 8.5 scenario in the time period from 1850 to 2120. For the time after 2120, we assume zero emissions to evaluate the response of the stabilising Earth System by 2300. Our results suggest that vegetation dynamics have a considerable influence on the changing global and regional climate. In the simulations, global mean tree cover extends by 2300 due to increased atmospheric CO2 concentration and global warming. Thus, land carbon uptake is higher and atmospheric CO2 concentration is lower by about 40 ppm when considering dynamic vegetation compared to the static pre-industrial vegetation cover. The reduced atmospheric CO2 concentration is equivalent to a lower global mean temperature. Moreover, biogeophysical effects of vegetation cover shifts influence the climate on a regional scale. Expanded tree cover in the northern high latitudes results in a reduced albedo and additional warming. In the Amazon region, declined tree cover causes a regional warming due to reduced evapotranspiration. As a net effect, vegetation dynamics have a slight attenuating effect on global climate change as the global climate cools by 0.22 K due to natural vegetation cover shifts in 2300.

The Impacts of Climate Change on Autumn North Atlantic Midlatitude Cyclones

2007 ◽  
Vol 20 (7) ◽  
pp. 1174-1187 ◽  
Author(s):  
Jing Jiang ◽  
William Perrie
Keyword(s):  
Climate Change ◽  
Climate Model ◽  
Global Climate ◽  
Global Climate Model ◽  
Co2 Concentration ◽  
Intergovernmental Panel ◽  
Northwest Atlantic ◽  
High Co2 ◽  
The North ◽  
Atlantic Hurricanes

Abstract This study explores how midlatitude extratropical cyclone intensities, frequencies, and tracks can be modified under warming-induced conditions due to enhanced greenhouse gas (GHG) concentrations. Simulations were performed with the Canadian mesoscale compressible community (MC2) model driven by control and high CO2 climate estimates from the Canadian Climate Centre model, the Second Generation Coupled Global Climate Model (CGCM2). CGCM2 simulations have effective CO2 concentration forcing, following the Intergovernmental Panel on Climate Change (IPCC) IS92a scenario conditions, which define a near doubling of CO2 concentrations by 2050 compared to the 1980s. The control and high CO2 conditions were obtained from years 1975–94 and 2040–59 of CGCM2 simulations. For the northwest Atlantic, the CO2-induced warming for this period (2040–59) varies from ∼1°–2°C in the subtropics, near the main development region for Atlantic hurricanes, to ∼1°C in the north. In simulations of northwest Atlantic storms, the net impact of this enhanced CO2 scenario is to cause storms to increase in radius, with marginal tendencies to become more severe and to propagate faster (although not statistically significant), and for the mean storm tracks to shift slightly poleward.

scholarly journals Solar-forced shifts of the Southern Hemisphere Westerlies during the late Holocene

2010 ◽  
Vol 6 (2) ◽  
pp. 369-384 ◽  
Author(s):  
V. Varma ◽  
M. Prange ◽  
F. Lamy ◽  
U. Merkel ◽  
M. Schulz
Keyword(s):  
Solar Activity ◽  
Southern Hemisphere ◽  
Ocean Circulation ◽  
Late Holocene ◽  
Large Scale ◽  
Climate Model ◽  
Global Climate ◽  
Global Climate Model ◽  
Latitudinal Position ◽  
Potential Factor

Abstract. The Southern Hemisphere Westerly Winds (SWW) constitute an important zonal circulation that influences large-scale precipitation patterns and ocean circulation. Variations in their intensity and latitudinal position have been suggested to exert a strong influence on the CO2 budget in the Southern Ocean, thus making them a potential factor affecting the global climate. In the present study, the possible influence of solar forcing on SWW variability during the late Holocene is addressed. It is shown that a high-resolution iron record from the Chilean continental slope (41° S), which basically reflects changes in the position of the SWW, is significantly correlated with reconstructed solar activity. In addition, solar sensitivity experiments with a comprehensive global climate model (CCSM3) are carried out to study the response of SWW to solar variability. Taken together, the proxy and model results strongly suggest that centennial-scale periods of lower (higher) solar activity caused equatorward (southward) shifts of the SWW during the past 3000 years.

scholarly journals Tropical Pacific Climate and Its Response to Global Warming in the Kiel Climate Model

2009 ◽  
Vol 22 (1) ◽  
pp. 71-92 ◽  
Author(s):  
W. Park ◽  
N. Keenlyside ◽  
M. Latif ◽  
A. Ströh ◽  
R. Redler ◽  
...  
Keyword(s):  
Global Warming ◽  
Climate Model ◽  
Southern Oscillation ◽  
Global Climate ◽  
Global Climate Model ◽  
Co2 Concentration ◽  
Tropical Pacific ◽  
Equatorial Pacific ◽  
Cold Bias ◽  
The Tropical Pacific

Abstract A new, non-flux-corrected, global climate model is introduced, the Kiel Climate Model (KCM), which will be used to study internal climate variability from interannual to millennial time scales and climate predictability of the first and second kind. The version described here is a coarse-resolution version that will be employed in extended-range integrations of several millennia. KCM’s performance in the tropical Pacific with respect to mean state, annual cycle, and El Niño–Southern Oscillation (ENSO) is described. Additionally, the tropical Pacific response to global warming is studied. Overall, climate drift in a multicentury control integration is small. However, KCM exhibits an equatorial cold bias at the surface of the order 1°C, while strong warm biases of several degrees are simulated in the eastern tropical Pacific on both sides off the equator, with maxima near the coasts. The annual and semiannual cycles are realistically simulated in the eastern and western equatorial Pacific, respectively. ENSO performance compares favorably to observations with respect to both amplitude and period. An ensemble of eight greenhouse warming simulations was performed, in which the CO2 concentration was increased by 1% yr−1 until doubling was reached, and stabilized thereafter. Warming of equatorial Pacific sea surface temperature (SST) is, to first order, zonally symmetric and leads to a sharpening of the thermocline. ENSO variability increases because of global warming: during the 30-yr period after CO2 doubling, the ensemble mean standard deviation of Niño-3 SST anomalies is increased by 26% relative to the control, and power in the ENSO band is almost doubled. The increased variability is due to both a strengthened (22%) thermocline feedback and an enhanced (52%) atmospheric sensitivity to SST; both are associated with changes in the basic state. Although variability increases in the mean, there is a large spread among ensemble members and hence a finite probability that in the “model world” no change in ENSO would be observed.

scholarly journals Atmospheric Modes of Variability in a Changing Climate

2006 ◽  
Vol 19 (22) ◽  
pp. 5934-5943 ◽  
Author(s):  
Jenny Brandefelt
Keyword(s):  
Southern Hemisphere ◽  
Northern Hemisphere ◽  
Spatial Patterns ◽  
Rossby Waves ◽  
Climate Model ◽  
Global Climate ◽  
Global Climate Model ◽  
Atmospheric Variability ◽  
Modes Of Variability ◽  
Coupled Global Climate Model

Abstract The response of the atmospheric circulation to an enhanced radiative greenhouse gas forcing in a transient integration with a coupled global climate model is investigated. The spatial patterns of the leading modes of Northern Hemisphere atmospheric variability are shown to change in response to the enhanced forcing. An earlier study showed that the spatial patterns of the leading modes in the Southern Hemisphere changed in response to the enhanced forcing. These changes were associated with changes in the propagation conditions for barotropic Rossby waves. This is, however, not the case for the Northern Hemisphere, where the propagation conditions are unchanged. Other possible mechanisms for the changes in the spatial patterns of the leading modes are discussed.

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