A 2XCO2 climate change scenario over Europe generated using a limited area model nested in a general circulation model 2. Climate change scenario

Abstract The steady-state extratropical atmospheric response to thermal forcing is investigated in a simple atmospheric general circulation model. The thermal forcings qualitatively mimic three key aspects of anthropogenic climate change: warming in the tropical troposphere, cooling in the polar stratosphere, and warming at the polar surface. The principal novel findings are the following: 1) Warming in the tropical troposphere drives two robust responses in the model extratropical circulation: poleward shifts in the extratropical tropospheric storm tracks and a weakened stratospheric Brewer–Dobson circulation. The former result suggests heating in the tropical troposphere plays a fundamental role in the poleward contraction of the storm tracks found in Intergovernmental Panel on Climate Change (IPCC)-class climate change simulations; the latter result is in the opposite sense of the trends in the Brewer–Dobson circulation found in most previous climate change experiments. 2) Cooling in the polar stratosphere also drives a poleward shift in the extratropical storm tracks. The tropospheric response is largely consistent with that found in previous studies, but it is shown to be very sensitive to the level and depth of the forcing. In the stratosphere, the Brewer–Dobson circulation weakens at midlatitudes, but it strengthens at high latitudes because of anomalously poleward heat fluxes on the flank of the polar vortex. 3) Warming at the polar surface drives an equatorward shift of the storm tracks. The storm-track response to polar warming is in the opposite sense of the response to tropical tropospheric heating; hence large warming over the Arctic may act to attenuate the response of the Northern Hemisphere storm track to tropical heating. 4) The signs of the tropospheric and stratospheric responses to all thermal forcings considered here are robust to seasonal changes in the basic state, but the amplitude and details of the responses exhibit noticeable differences between equinoctial and wintertime conditions. Additionally, the responses exhibit marked nonlinearity in the sense that the response to multiple thermal forcings applied simultaneously is quantitatively different from the sum of the responses to the same forcings applied independently. Thus the response of the model to a given thermal forcing is demonstrably dependent on the other thermal forcings applied to the model.

Download Full-text

An examination of climate sensitivity for idealised climate change experiments in an intermediate general circulation model

Climate Dynamics ◽

10.1007/s003820000083 ◽

2000 ◽

Vol 16 (10-11) ◽

pp. 833-849 ◽

Cited By ~ 95

Author(s):

P. M. de F. Forster ◽

M. Blackburn ◽

R. Glover ◽

K. P. Shine

Keyword(s):

Climate Change ◽

General Circulation Model ◽

Climate Sensitivity ◽

General Circulation ◽

Circulation Model

Download Full-text

Regional aspects of global climate change simulations : Validation and assessment of climate response over Indian monsoon region to transient increase of greenhouse gases and sulfate aerosols

MAUSAM ◽

10.54302/mausam.v52i1.1691 ◽

2021 ◽

Vol 52 (1) ◽

pp. 229-244

Author(s):

K. RUPA KUMAR ◽

R. G. ASHRIT

Keyword(s):

Climate Change ◽

Greenhouse Gases ◽

General Circulation ◽

Regional Scale ◽

Circulation Model ◽

Ocean General Circulation Model ◽

Change Scenario ◽

Climate Projections ◽

Sulfate Aerosols ◽

Monsoon Climate

The regional climatic impacts associated with global climatic change and their assessment are very important since agriculture, water resources, ecology etc., are all vulnerable to climatic changes on regional scale. Coupled Atmosphere-Ocean general circulation model (AOGCM) simulations provide a range of scenarios, which can be used, for the assessment of impacts and development of adaptive or mitigative strategies. Validation of the models against the observations and establishing the sensitivity to climate change forcing are essential before the model projections are used for assessment of possible impacts. Moreover model simulated climate projections are often of coarse resolution while the models used for impact assessment, (e.g. crop simulation models, or river runoff models etc.) operate on a higher spatial resolution. This spatial mismatch can be overcome by adopting an appropriate strategy of downscaling the GCM output. This study examines two AOGCM (ECHAM4/OPYC3 and HadCM2) climate change simulations for their performance in the simulation of monsoon climate over India and the sensitivity of the simulated monsoon climate to transient changes in the atmospheric concentrations of greenhouse gases and sulfate aerosols. The results show that the two models simulate the gross features of climate over India reasonably well. However the inter-model differences in simulation of mean characteristics, sensitivity to forcing and in the simulation of climate change suggest need for caution. Further an empirical downscaling approach in used to assess the possibility of using GCM projections for preparation of regional climate change scenario for India.

Download Full-text