CLIMATE CHANGE WILL MEAN BIG SHIFT FOR INDIA’S MONSOONS
UAE research suggests that Arabian Peninsula can also expect weather upheaval, writes Daniel Bardsley
Over the centuries, life in Arabia became shaped by the hot and dry climate, while in other parts of the world communities have adapted to, and become dependent on, climates that are very different.
In northern India, where about 600 million people live in areas where monsoon rains are essential to agriculture. Without them, life would alter dramatically.
The importance of the annual rain has been brought into sharp focus by a study by New York University Abu Dhabi researchers.
Their modelling has indicated that climate change will cause low-pressure systems that create the Indian monsoons to shift northwards. The resulting reduction in rainfall for some areas could have a major effect on agriculture.
What is more, the same human-generated upheavals could influence the climate in parts of Arabia.
A key resource to the researchers, whose study was published recently in the Proceedings of the National Academy of Sciences of the United States of America, has been India’s database of weather records which goesback to at least 1900. This has proved useful for identifying patterns of change and testing models of how the climate may change.
Using the data with a complex system of mathematical modelling, the researchers forecast that, by the end of this century, overall monsoon synoptic activity – weather systems that last a few to several days and span a few hundred to a few thousand kilometres – will have decreased by 45 per cent.
There is also a slight northward shift in the winds that create the monsoons.
“We found there’s a very drastic decrease in the lowpressure systems,” said Dr Ajaya Ravindran, a senior scientist the university’s Centre for Prototype Climate Modelling and one of the study’s authors.
“There’s a decline in the seasonal mean precipitation and a shift towards the foothills of the Himalayas.”
There was a 10 per cent forecast increase in the number of low-pressure systems that develop over land, but much larger reduction in the number developing over water, which results in an overall decline.
Dr Ravindran says that the results of the study should be treated with caution because they are the product of only one model.
Typically, when it comes to forecasting how climate change will affect weather patterns, the results of several models are compared and an average, called the ensemble mean, generated.
“You take at least 10 models from agencies. Every model should simulate the same scenario,” Dr Ravindran said.
Yet earlier models have forecast a similar effect and these latest results tie in with observational data indicating that a reduction in average seasonal rainfall has taken place.
“We have already found from observations that the rainfall in Kerala and southern places is decreasing. This will further reinstate that drying,” Dr Ravindran said.
What sets the university’s research apart from previous attempts is its level of detail.
It uses a High Resolution Atmospheric Model, developed by researchers at the Geophysical Fluid Dynamics Laboratory in Princeton, New Jersey, with horizontal grid spaces of 50km.
That offers more precision than many other models, which are often global and based on much lower resolution.
“Quite a lot of computing power is needed for that,” Dr Ravindran said. As is typically the case with climate change, the effects are not consistent and will vary from one place to another. There are areas even in southern India that will have more rainfall, even if the average rainfall in the region overall is likely to decline.
“There are areas with more rainfall and some with less rainfall. That will disturb the human settlements, but exact prediction, it’s very difficult,” Dr Ravindran said.
The significant effects that a loss of monsoons can have are vividly illustrated by a look at the history of Arabia.
A 2015 study indicated that every 23,000 years or so there were wet phases in the Arabian peninsula with monsoons penetrating into the interior, creating a lush
habitat. When the monsoons disappeared, so did the habitat. Only a small edge of Arabia experiences the remnants of this monsoon, such as the area around Salalah in Oman, which has a lush summer climate during the khareef monsoon season.
Dr Ravindran says the changes his model forecasts will not cause lush areas of India to become desert. But they could have a significant impact on the agriculture that becomes possible in the affected areas.
“We want to extend it and look into details of what happens to precipitation on a local scale, and how much it reduces and where it reduces,” he said.
The other authors of the study, which is titled Decline and Poleward Shift in Indian Summer Monsoon Synoptic Activity in a Warming
Climate, are Dr Sandeep Sukumaran, a research scientist at the university’s Centre for Prototype Climate Modelling, Dr V Praveen, a senior support scientist at the centre, and Dr T P Sabin, who has worked at the university and is now at the Centre for Climate Change Research of the Indian Institute of Tropical Meteorology in Pune, Maharashtra state.
The department of earth and planetary science at the University of California, Berkeley, also contributed to the research.
Having analysed in depth the way that climate change could affect the pattern of low-pressure systems in India, the researchers at the Abu Dhabi university are turning their attention to the climatic upheavals that the Arabian Peninsula can reasonably expect.
Given that some parts of India will be facing major changes, many people in Arabia will no doubt be keen to learn about what their part of the world will encounter.
The NYUAD study suggests that monsoon activity in India will have fallen by 45% by the end of this century