Climate change is heating up the global ocean. Alongside sea level rise, this means that rare extreme weather events, which would normally occur once every century, will now occur once every year. (Photo: Getty Images)

Climate Change: That sinking feeling

> A new UN report on the effects of climate change on the ocean and the cryosphere makes some dire predictions > Lounge takes a look at how India will be affected by the warming seas and melting Himalayan glaciers

opics Climate ChangeIPCCUnited Nations India

"All over the world, mean temperatures rose by a few degrees each year. The majority of tropical areas rapidly became uninhabitable, entire populations migrating north or south from temperatures of a hundred and thirty and a hundred and fortydegrees. Once-temperate areas became tropical, Europe and North America sweltered under continuous heat waves, temperatures rarely falling below a hundred degrees. Under the direction of the United Nations, the colonisation began of the Antarctic plateau, and of the northern borders of the Canadian and Russian continents."

Science fiction? Yes it is, a passage from J.G. Ballard’s eerie novel from 1962, The Drowned World. Of course, this was before we had any inkling of climate change, so Ballard’s fictional vision was realized by him imagining the sudden appearance of violent solar storms which lasted several years and burnt away the earth’s ionosphere. Writing as he was just a decade on from the birth of a geological epoch that many scientists call the Anthropocene, when human actions and activities started changing the world like never before, Ballard wouldn’t have known about runaway carbon emissions playing havoc with the climate.

Graphic: Ahmed Raza Khan/Mint
Graphic: Ahmed Raza Khan/Mint

And yet, on 25 September, when the UN’s Intergovernmental Panel on Climate Change (IPCC) published an almost 1,200-page dossier, the IPCC Special Report On The Ocean And Cryosphere In A Changing Climate (SROCC), the revelations did read like science fiction, because it spoke of future life on our planet, a planet that seemed unrecognizable from the one we live in. It spoke of a world of multi-metre sea-level rise, vanished Himalayan glaciers, a Greenland denuded of permafrost and the collapse of the Antarctic ice sheet. It was a world of dead zones in the oceans, of category 5 cyclones hitting multiple times a year, and coastal cities and populations devastated by extreme weather events. These are alarming revelations, couched in the careful, analytical voice of science (see box, IPCC SROCC in numbers)

A survey and summary of current available scientific knowledge about the effects of anthropogenic (man-made) greenhouse gas emissions, the SROCC is the third and final special report to appear as part of IPCC’s Assessment Review 6 (AR6). The first of these was the ground-breaking one from last October, which detailed the planetary effects of a failure to limit global warming to a rise of 1.5 degrees Celsius above mean temperatures from the time of the Industrial Revolution. A second report, on the effects of climate change on land, followed this August, and now this report on the oceans and the cryosphere. Already, scientists from around the world are working on the AR6 Synthesis Report, which will be presented in 2022.

What the report says

The world’s oceans have, since the baseline year of 1970, absorbed 90% of the excess heat generated by greenhouse gas emissions. Between 1993-2017, the rate of ocean warming has doubled, as compared to 1969-93. Marine heat waves have doubled since 1982, and they have also become more long-lasting, more intense and more extensive. And because the ocean has absorbed 20-30% of anthropogenic CO2, it has undergone increased acidification, with a loss of oxygen from the surface down to a depth of 1,000m in many areas (see box, Effects Of Climate Change On Oceans).

People wading through a flooded street in Kurla, Mumbai, in September.
(Photo: Hindustan Times)People wading through a flooded street in Kurla, Mumbai, in September.

These changes have already triggered a host of consequences. A warmer ocean means a rise in extreme weather events, like devastating storm surges in coastal areas and the increased likelihood of category 4 and 5 tropical cyclones making landfall. Marine heat waves are the biggest threat to coral reefs, while increased ocean acidification has the potential to devastate fish stocks worldwide.

“So far, we have been bothered about extremes over land, so now this report has brought to light the extremes happening over the ocean, which have an impact on life over land," says Roxy Mathew Koll, a climate scientist at the Indian Institute of Tropical Meteorology (IITM) in Pune. “None of the earlier IPCC reports had dealt with this kind of extremes, like extreme El Niño cases or marine heat waves, or extremely severe tropical cyclones."

A lead author on the SROCC, he stresses on the fact that we need to note the many factors working simultaneously. “We have multiple events happening at the same time," he says. “So you have the sea level rise, which is at around 30-40cm per century. On top of that, you have extreme rainfall events and tropical cyclones making landfall along the coasts and fisheries are getting a hit because of marine heat waves. All these things are happening simultaneously."

The Big Melt

Speaking of different events occurring simultaneously, permanent ice at the Poles and high mountain glaciers have also been melting at a record rate. Between 2006-15, the Greenland ice sheet lost ice at the rate of 278 gigatonnes (Gt)/year; the Antarctic ice sheet at 155 Gt/year; and worldwide glaciers (outside Greenland and Antarctica) at 220 Gt/year. The Polar melting is raising global sea levels at a current rate of .77mm a year, forming an additional layer of extreme weather hazards.

Under current emission pathways (see box, Different Warming Scenarios), which chart out both the near term (till 2050) as well as future consequences (2100 and beyond), every aspect of planetary balance is set to go awry. These effects are being felt in India as well, and as time goes on, these can become acutely worrying. “This is a very timely report that emphasizes the mountains and the oceans. And specifically those two are very important in the context of South Asia. On one side we are covered with the Himalaya, and we have the ocean on three sides," says Aditi Mukherji, principal researcher at the International Water Management Institute (IWMI), and a review editor on the SROCC chapter that deals with high mountains.

A poignant bit of news made the headlines on 22 September.Two hundred and fifty people, including children and climate scientists, held a funeral and farewell march for a glacier in the Swiss Alps. The Pizol glacier was deemed to have lost so much mass that it could no longer be called a glacier.

The biggest threat to high mountain ranges around the world, home to 670 million people, comes in the form of this loss of glaciers. As temperatures rise globally, at high altitudes, the corresponding heating is even greater. The SROCC examines the evidence and comes to the sobering conclusion that mountain glaciers worldwide will exhaust most of their water by 2050. In some areas, such as the Andes and the European Alps, the glaciers have already gone past this point of peak melt, and are now just withering away. In the Himalaya, this point will be reached around 2050 (see box, Glacier Loss In High Mountain Asia).

One of the biggest effects will be felt downstream, with some 580 million people living in the Ganges basin alone. “The SROCC shows severe impacts of climate change on Himalayan glaciers and, consequently, on Himalayan rivers. This has direct consequences on water security of the entire Indo-Gangetic Basin (IGB). Livelihoods in the mountains and plains are critically mediated by snow melt (e.g. for apple growers in Himachal) and river flow (e.g. farmers in Uttar Pradesh) and the SROCC findings have implications for the heavily populated IGB," says social scientist Chandni Singh of the Indian Institute for Human Settlements (IIHS), a lead author with the IPCC AR6 Working Group II, on email.

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