Sensitivity is the degree to which a system is affected, either adversely or beneficially, by climate-related stimuli. Climate-related stimuli encompass all the elements of climate change, including mean climate characteristics, climate variability, and the frequency and magnitude of extremes. The effect may be direct (e.g., a change in crop yield in response to a change in the mean, range, or variability of temperature) or indirect (e.g., damages caused by an increase in the frequency of coastal flooding due to sea-level rise). The term climate sensitivity refers to the steady-state increase in the global annual mean surface air temperature associated with a given global-mean radiative forcing. It is common practise to use CO2 doubling as a benchmark for comparing GCM climate sensitivities. Thus in practise the climate sensitivity may be defined as the change in global-mean temperature that would ultimately be reached following a doubling of CO2 concentration in the atmosphere (e.g. from 275 ppmv to 550 ppmv). The IPCC has always reported the likely range for this quantity to be between 1.5º and 4.5ºC, with a 'mid-range' estimate of 2.5ºC. Each GCM has different climate sensitivity, depending on the representation of various feedback processes in the model, including water vapour. It is generally assumed that the climate sensitivity of a model is approximately constant over the range of forcings expected for the next century. The climate sensitivity of a model is also largely independent (±10%) of the specific combination of different forcing factors (solar, aerosols, CO2, CH4, etc.) that produce a given global-mean forcing. The range of climate sensitivities in the DDC models is from about 2.5ºC to 4.0ºC (IPCC DDC).
Published in Chapter:
Climate Change Impact on the Water Resources of the Limpopo Basin: Simulations of a Coupled GCM and Hybrid Atmospheric-Terrestrial Water Balance (HATWAB) Model
Berhanu F. Alemaw (University of Botswana, Botswana) and Thebeyame Ronald Chaoka (University of Botswana, Botswana)
Copyright: © 2018
|Pages: 24
DOI: 10.4018/978-1-5225-3440-2.ch012
Abstract
This chapter aims to evaluate the impacts of climate change on both hydrologic regimes and water resources of the Limpopo River Basin in southern Africa. Water resources availability in the basin, in terms of, seasonal and annual runoff (R), soil moisture (S) and actual evapotranspiration (Ea) is simulated and evaluated using the hydrological model, HATWAB. These water balances were computed from precipitation (P), potential evapotranspiration (Ep) and other variables that govern the soil-water-vegetation-atmospheric processes at 9.2km latitude/ longitude gird cells covering the basin. The 1961-90 simulated mean annual runoff reveals mixed patterns of high and low runoff across the region. Although relatively small changes in runoff simulations are prevalent among the three climate change scenarios, generally the OSU simulated relatively high runoff compared to the UKTR and HADCM2 GCMs.