Study: climate change warming Asian waters, altering monsoon

Study: climate change warming Asian waters, altering monsoon

Each year as temperatures rise across India, farmers look to the sky and pray for rain.

The all-important monsoon forecast becomes a national priority, with more than 70 percent of India's 1.25 billion citizens engaged in agriculture and relying on weather predictions to decide when they will sow their seeds and harvest their crops.

But getting the forecast right remains a challenge, thanks to the complex—and still poorly understood—ways in which South Asia's monsoon rains are influenced by everything from atmospheric and ocean temperatures to air quality and global climate trends. Even the amount of ice in Antarctica is suspected to have an impact.

And it's only getting harder to figure out, scientists say, as the monsoon becomes increasingly erratic.

A new study released Friday in the journal Science Advances helps clear up a bit of the mystery, by showing that man-made climate change is responsible for most of the change seen in ocean surface temperatures near the equator across Asia, which in turn affect regional rainfall patterns including the Indian monsoon.

By showing that link, the study indicates future ocean warming in the region, which could in turn increase the amount of rainfall during monsoons, strengthen cyclones and increase precipitation over East Asia.

"This has important implications for understanding changes in rainfall patterns for a large, and vulnerable population across Asia," said oceanographer Evan Weller, who led the research team while he was at Pohang University of Science and Technology in South Korea, before recently shifting to Monash University in Australia.

The study looks specifically at a mid-oceanic body called the Indo-Pacific Warm Pool, which holds some of the world's warmest seawaters and spans the western Pacific to the eastern Indian Ocean.

Scientists have long known that India's monsoons are partly influenced by that warm pool. And they've known that the pool has been expanding—and warming—for decades. That expansion and warming have already caused some sea rise around islands in Asia.

It wasn't entirely clear why the pool was changing, until now.

The video highlights that the expansion of the Indo-Pacific warm pool (IPWP) over the past 60 years is dominantly attributable to man-made greenhouse gas increase. The top panel compares the observed IPWP change over time in red which continues to grow with the long-term average position from 1971-2000 represented by the dashed line. The second panel shows the same as the top panel but using multiple climate model simulations integrated with human influences (greenhouse gases, aerosols, and other anthropogenic forcing agents) combined with natural (solar and volcanic activities) forcings. A large growth of the IPWP can be seen. The third panel shows that using multiple climate model simulations integrated with no human influences does not cause a long-term expansion of the IPWP. The bottom panel summarises these findings by showing the size of the IPWP over time from the observations (black line), and climate model simulations with and without human influences in green and blue lines, respectively, as a percentage of the size of a long-term average from 1971-2000. The overall increase over the past 60 years is much larger than what occurs due to climate fluctuations such as during El Niño-Southern Oscillation events. Credit: Produced by Evan Weller using MATLAB

Weller and his team compared data observations with several climate models, and deduced that rising greenhouse gases along with aerosols and other atmospheric pollutants were the dominant cause of the pool's warming and expansion over the past 60 years, though regional climate variations also had some effect.

"This wasn't entirely surprising. We've long suspected climate change to be behind the changes, but no one had yet proven it," Weller said. What they didn't expect was to find that the western portion of the pool, near India, was expanding more than the eastern part in the Pacific. "We don't really know why. We'll try to figure that out next."

But one thing is clear: If climate change trends continue, and by most indications they will, forecasters will have to consider the warm pool in their monsoon predictions. And by demonstrating how greenhouse gases are the dominant driver of changes in the warm pool, the team has added another dimension that can help improve climate models.

Asia, in general, could face significant consequences from this trend: more storm activity over East Asia, and stronger South Asian monsoons between June and September.

That sounds like good news for water-scarce India, but probably isn't. Most of that rain would likely fall before the monsoon front reaches land. Already, studies by the Indian Institute of Tropical Meteorology show a declining trend in precipitation over land.

Still, climate modeling is complex, and models still have their biases and limitations. Focusing so specifically on the warm pool may obscure the larger picture, some suggested, especially in the Pacific where there are many other factors at play.

"My only concern is that treating the western Pacific warm pool in isolation provides very limited insight," said climatologist Michael Mann, director of the Earth System Science Center at Pennsylvania State University. He was not involved in the study. "One has to view it as part of the larger tropical Pacific coupled ocean-atmosphere system and the dynamics of the El Nino/Southern Oscillation, and how they may change in a changing climate."

Anxious to improve its forecasting, India is investing at least $43 million through 2017 to buy more powerful computers and better technology that can help specialists make more accurate calculations and models of seasonal weather forecasts. Meanwhile, researchers from across the world are launching one study after another to better understand the many dynamics involved.

"It is not so easy to predict the monsoon," said meteorologist B.P. Yadav, a spokesman for the Indian Meteorological Department. "There is variability from region to region, time to time, and then the rains move in different stages across the land."

Indian meteorologists had announced this year's monsoon would be normal, only to watch the rains make landfall a week late in the southern state of Tamil Nadu and then stall repeatedly on their month-long progression north. At one point, officials urged farmers to wait to sow until they actually saw the raindrops falling from the sky.

But on Friday, when the monsoon was scheduled to hit New Delhi, the sky turned ochre and millions in the long-sweltering Indian capital delighted in the on-time relief of rain.

Explore further

Living fossils in the Indo-Pacific Warm Pool: A refuge for thermophilic dinoflagellates during glaciations

More information: "Human-caused Indo-Pacific warm pool expansion," Science Advances,
Journal information: Science Advances

© 2016 The Associated Press. All rights reserved.

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Jul 02, 2016
Something else to factor in, especially for the Precipitation over land portion, and that is the amount of radio, radar and microwave radiation that we put into the atmosphere and will heat water droplets that correspond properly to the size of the wavelength. Before cable was widespread I used to see clear circles of No Clouds around larger cities, even when there was heavy cloud cover over surrounding areas, the area of the city, in a circular or overlapping circular patterns, such as radio stations would provide.

We look a lot at the gasses that we pump into the atmosphere, we also need to look at the megawatts and megajoules of energy pumped into it as well, and which frequencies are those that do the most damage, precipitation wise. It is certainly something to factor in since we are going to ubiquitous radio comms all the time with our smartphones.

Jul 02, 2016
Fossil fuels by a ludicrous amount outweighs any other pollution on earth, though yes every potential cause of pollution needs to be addressed.

Jul 02, 2016
It is not just the size of the individual waves, but also their overlaps and Full Saturation of Many ranges on the Electromagnetic spectrum, from household heat and electrical use to the radio transmission Terawatts, when all added together as one stack, not looking at any specific wavelength, but the whole saturation, THAT is the problem, too many moire patterned nodal imposed wavelets that DO correspond to water and ice droplet sizes as well as micrometer dust for it to condense on. No condensation if the temp is even a little too high. Maybe you should do a lil 'back of the envelope' work and really SEE how much we pump into the atmosphere. We are going to be like the proverbial frog in the pot, our electromagnetic radiation levels, which we are told are safe, keep rising in number of distribution points but also in amount of power used. This is a world wide phenomenon, and not inconsiderable.

Jul 02, 2016
Meh, our electromagnetic energy output peaks in the infrared. That's guaranteed by thermodynamics.

Jul 02, 2016
You fanbois can go home now. "Climate Change" cannot be stopped. Nothing to talk about anymore.

Jul 02, 2016
Shootist said:
You fanbois can go home now. "Climate Change" cannot be stopped. Nothing to talk about anymore.

So, Shooter, which side of the question are you on today? Normally you spout about global warming being a scam and quote a nonogenarian to ensure us that the Polar bears are going to be fine... Now you are saying it is too late to stop it.

So, is it a scam or is it real and it can't be stopped (according to you).

Jul 03, 2016
'ol shooty got some inner conflict he's struggling to deal with, but that's always been the case :D

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