Effect of climate change on seasonal monsoon

20 Março 2018, 10:00 • Shiv Kumar Singh

Global warming and climate change is one of the most extensively researched and discussed topical issues affecting the environment. Although there are enough historical evidence to support the theory that climate change is a natural phenomenon, many research scientists are widely in agreement that the increase in temperature in the 20th century is anthropologically related. The associated effects are the variability of rainfall and cyclonic patterns that are being observed globally. In Southeast Asia the link between global warming and the seasonal atmospheric flow during the monsoon seasons shows varying degree of fuzziness. This study investigates the impact of climate change on the seasonality of monsoon Asia and its effect on the variability of monsoon rainfall in Southeast Asia. The comparison of decadal variation of precipitation and temperature anomalies before the 1970s found general increases which were mostly varying. But beyond the 1970s, global precipitation anomalous showed increases that almost corresponded with increases in global temperature anomalies for the same period. There are frequent changes and a shift westward of the Indian summer monsoon. Although precipitation is observed to be 70% below normal levels, in some areas the topography affects the intensity of rainfall. These shifting phenomenon of other monsoon season in the region are impacting on the variability of rainfall and the onset of monsoons in Southeast Asia and is predicted to delay for 15 days the onset of the monsoon in the future. The variability of monsoon rainfall in the SEA region is observed to be decadal and the frequency and intensity of intermittent flooding of some areas during the monsoon season have serious consequences on the human, financial, infrastructure and food security of the region. The global circulation in terms of precipitation is an important element for the functionality of the Earth's system. It helps to regulate the temperature of the Earth by transporting heat from the tropics to the higher latitudes. However, this system is vulnerable to long-term temperature fluctuations, more commonly termed as climate change. Climate change is currently debated as an anthropologically enhanced phenomenon. Many scientists of today have been trying to quantify climate change and its relation with other environmental systems. Arguably one of the most heavily dependent upon weather system is the monsoon season of Southeast Asia. While there are many literatures available on the interactivity of the monsoon seasons, the impact of climate change in terms of rising temperatures on monsoon rainfall intensities in Southeast Asia has received little attention. This study has given some insights on the connections between global warming and monsoon rainfall. It is evident that the distribution of monsoon rainfall is greatly influenced by a number of weather systems, such as the Arctic Oscillation, Siberian High and Western Pacific Subtropical High, as well as the complex Asian topography, i.e. the Tibetan Plateau. The EAWM is regulated by the Arctic ice which influences the SH weather system. The EASM is affected by the westward shift of the WPSH and consequently impacting on the distribution and variability of monsoon precipitation. Excessive monsoon flooding which has become frequent in recent years in parts of Southeast Asia remain an issue to be overcome. Understanding the shift and predicting changing trends of monsoon may be central to managing the floods that impact on millions of people, damage to lives and property, destruction of ecology and farmlands and the long term effect on food security.