Publication Details

The Impact of Climate Change on the Hydro-climate of Malaysia Based on IPCC Fifth Assessment Report

Weather and climate are among the foremost factors that determine how a society develops in a geographical region. Daily fluctuations of temperature are called weather, while climate is typically the average state of the atmosphere observed over a finite time period for a number of years. The social, economic and physical infrastructure of a geographical region such as Malaysia has evolved from the adaptation of that region’s society to the prevailing climate and to the hydrological conditions brought about by that climate over decades or, as in the case of Malaysia, over centuries. The frequency of occurrence and magnitudes of such phenomena as typhoons, floods and droughts have a profound influence on the habitability of a region and on the social and economic activities of that region’s population which tries to moderate the stresses brought about by those climatic/hydrologic extreme events. Recently, the Intergovernmental Panel on Climate Change (IPCC) adopted Representative Concentration Pathways (RCPs) for its greenhouse gas emission scenarios for its Fifth Assessment Report (AR5) in 2014 which superseded the Special Report on Emissions Scenarios (SRES) projections published in 2000. Furthermore, AR5 utilized the simulation results of most recent versions of the climate models, which improved their representation of earth climate compared to those utilized in the Fourth Assessment Report (AR4). Flato et al. (2013) evaluated the global climate models that were used in the preparation of AR5 in comparison to those models used in AR4 and concluded that: i. The ability of climate models to simulate surface temperature has improved in many important aspects relative to the generation of models assessed in the AR4; ii. There is very high confidence that models reproduce the general features of the globalscale annual mean surface temperature increase over the historical period, including the more rapid warming in the second half of the 20th century, and the cooling immediately following large volcanic eruptions; iii. The simulation of large-scale patterns of precipitation has improved somewhat since the AR4, although models continue to perform less well for precipitation than for surface temperature;2 iv. Models are able to capture the general characteristics of storm tracks and extratropical cyclones, and there is some evidence of improvement since the AR4; v. Many models are able to reproduce the observed changes in upper ocean heat content from 1961 to 2005 with the multi-model mean time series falling within the range of the available observational estimates for most of the period; vi. The simulation of the tropical Pacific Ocean mean state has improved since the AR4, with a 30% reduction in the spurious westward extension of the cold tongue near the equator, a pervasive bias of coupled models; vii. Many important modes of climate variability and intra-seasonal to seasonal phenomena are reproduced by models, with some improvements evident since the AR4; viii. Climate and Earth System models are based on physical principles, and they reproduce many important aspects of the observed climate.