Climate change may not alter Southeast Asian Monsoons

Climate change is a looming threat of the 21st century, and seems to be the talk of the town.

One way that the human impact on the globe is being felt is through the weather- drought or flooding is become more common, as well as "freaky" weather events.

Take for instance, the disastrous rains that battered the driest southern city of India- Chennai, late last year. Chennai hadn't experienced such unprecedented rainfall and ensuing devastation in over a century!

One of the most influential weather events seen in many parts of India, including Chennai and Southeast Asia are the summer and winter monsoons.

A monsoon is a result of change in the direction of the strongest winds, causing seasonal 'dry' and 'wet' climate.

The summer monsoon seen in these areas of the world normally brings a humid climate and huge downpours of rain, while the winter monsoon is a drier season and is sometimes associated with droughts due to the Himalayas preventing cool air reaching southern India and Sri Lanka.

Monsoons not only deliver water to billions of people but are also a vital part of the economy of these countries. If the summer monsoon is late or weak, the economy suffers as fewer people and businesses can grow food, to either sell it or feed their families. Disruption to the strength of the monsoon in a year would lead to catastrophic effects to people all over the world, and especially to the billions of people living in India and Southeast Asia.

Scientists believe that when the levels of greenhouse gases rise to a certain stage they can affect monsoon strength.

Many previous studies have tried to predict if and when this could happen to possibly warn future leaders and people, of the dangers of rising greenhouse gases. These studies have shown that monsoons would shut down abruptly when the level of greenhouse gas concentration reaches these critical thresholds, sometimes dubbed as a "tipping point".

However, a new study by Drs. William R. Boos and Trude Storelvmoa from the Department of Geology and Geophysics at Yale University has shown that the way these tipping points have been predicted are wrong, and fail to take into account critical forces that act on monsoon strength and circulation.

The most critical of these forces is adiabatic cooling- that describes the observation that when air rises, it cools down. For example, you would be able to feel adiabatic cooling if you walked up a mountain, like the Himalayas, where the top is much colder than the bottom or base-camp. Observations show that this cooling effect has strong stabilizing effects on monsoons and on the tropical atmosphere in general.

However, adiabatic cooling was not taken into account when older studies predicted the tipping points for a monsoon. But the new model in the current study incorporating this effect, predicts that monsoons will not shut down abruptly in response to human-induced climate changes- which is good news!

The earlier concept suggested that twice the amount of greenhouse gases would decrease the amount of rain from a monsoon.

The current study proves that it is incorrect. To support their theory, the researchers used the global climate model, which is a computer simulation of the global climate system. This is the closest thing scientists have in predicting the upcoming weather systems.

In future, scientists could use the new model for forecasting how a monsoon will behave. Such studies provide valuable information to policy makers when they make critical decisions to stem climate change.

So don't throw away your umbrellas yet, because monsoons are here to stay!

Image credit: Kamaljith K V, on Flickr


Graduate Study MPhil and PhD
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