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Bengaluru: The terrifying new scientific report released this week by the United Nations Intergovernmental Panel on Climate Change (IPCC) has revealed that heat waves in the oceans are drastically changing marine ecosystems and increasing the possibility of extreme weather conditions by a hundred fold.

Research on marine heat waves is growing over time as heat waves have now become a common phenomenon across the world.

This is also the first time the IPCC has devoted so much attention to this subject. Over a hundred scientists from more than 30 countries contributed to the study — titled ‘Special Report on the Ocean and Cryosphere in a Changing Climate’ — that was released during a meeting of an intergovernmental panel in Monaco Wednesday, a day after the UN Climate Action Summit in New York.

Impact on fishing

The response of the oceans to increasing global temperatures is often slower because of a process called climate inertia. The report is even more alarming considering this is likely the slowest response from the oceans to the warming of climate.

The report stated that globally, heatwaves in the oceans have doubled since just over 30 years ago — from 1982. Within 2081, the frequency of the heat waves is expected to increase 20 to 50 times depending on how much emissions are curbed.

Also crucial is the severity of El Nino — in 2015, India had suffered the repercussions of an extremely warm El Nino, which triggered droughts across the country.

El Nino also comes in conjunction with marine heatwaves, which affect delicate ecosystems like coral reefs that sustain a quarter of all aquatic species.

Independently, heatwaves wreak havoc among fish ecosystems, thereby, directly affecting the fishing industry. This has been occurring over the past few decades across the globe, and ultra-efficient mechanisation of fisheries has combated loss to industry while also over exploiting resources beyond sustainability.

In India, there is ample evidence that fisheries have been affected steadily over the past several years. In response, states like Tamil Nadu, Kerala, Karnataka and Maharashtra have stepped up efforts in utilising increased mechanisation. As a result, they have exceeded their maximum sustainable yield (MSY) — the highest amount of annual catch that can be sustained — several times.

Despite this level of over-capitalisation, there is evidence that fish yields started declining by the 1970s and 80s in India, and is now expected to decline even more as the ocean acidifies and warms.

There is also the problem of fish kills — a common occurrence in the summer due to dumping of chemical wastes in rivers, which further aids and abets acidification when draining into the ocean, propagating the process exponentially.

As glaciers melt, the excess dumping of fresh water into the salty ocean changes the oceans’ dynamics. Nutrients in the ocean settle towards the bottom, and the constant churning of oceans move them across the breadth of it. This tossing and turning feeds phytoplankton that floats on the water and is food for zooplankton, which in turn is food for small fish. These are then devoured by larger fish, thus moving up the food chain.

Freshwater floats over saltwater, and this prevents nutrients from reaching phytoplankton as the top layers of the ocean get constantly replenished superficially with freshwater, preventing mixing with the bottom layers.

Such a phenomenon is what causes increased extreme weather conditions, across the world and India, but is also responsible for not sustaining phytoplankton. This in turn affects all of the marine ecosystem in a cascading manner.

Ocean heat waves also cause glaciers to melt under the surface of the water, and the rising freshwater does enable mixing of nutrients. However, the effect reduces as the distance from glaciers increases and is more prominent closer to the poles. In India, glaciers belong to the Himalayan region and increase freshwater melt close to the surface, primarily. 

Additionally, currents change as well, displacing existing fish ecosystems further and further away from the coast, and away from temperate or tropical regions.

Coastal states all around the country and the world will see a drastic loss in the fishing industry, and also increased cases of poisoning due to marine acidification and micro plastic pollution. 


Also read: Salmon farmers are trying to breed more climate change-resistant fish


Rising sea levels

Last year, the IPCC recommended that the world leaders must take rapid action to ensure that the global increase in temperatures remains within 1.5 degrees: also the objective of the Paris agreement.

In the present emission scenario, the world could see a rise of one metre of sea level by the end of the century. This would effectively sink coastal cities like Chennai and Mumbai. Studies have already shown that the sea is creeping into the coastal land in Chennai.

As sea level rises, storm surge events increase. Floods will also intensify and increase in frequency with each passing year. 

The IPCC report stated that historic 100-year floods will occur annually across coastal cities by 2050 even in the most positive scenario, which is dubbed ‘the Representative Concentration Pathway 2.6’. R2.6 is the lowest emission scenario in our climate models today. However, the high emission scenario, RCP8.5, is the path the world is on today. 

Studies have also shown that there has been a severe impact on the Indian weather cycle. Monsoon in the country is expected to decline by 45 per cent, according to independent studies, and both in India and elsewhere in the tropical belt, summers would get hotter and longer while monsoons will become shorter but more intense.

Low-lying areas, disproportionately occupied by members of underprivileged communities would be most affected, and potentially be fully lost to water.

Melting of ice, on the other hand, is doubly dangerous because of a feedback loop: ice is white and reflects sunlight, with the poles effectively acting as an umbrella, shielding the earth from the sun’s heat. This is called the ‘albedo’ effect. Once ice melts, not only does this effect disappear, but the dark-coloured land or water that replaces this ice absorbs even more heat.

The largest volume of freshwater melt comes from Greenland, but in the Indian subcontinent, the Hindu Kush mountain range poses a big threat. Also called the ‘third pole of the world’, the Himalaya-Karakoram glaciers make up the large ice mass in lower latitudes. 

There are millions of people who survive on the fertility brought upon by these glaciers each year, and most of them are currently at increasing risk of extreme flooding, mudslides and a sharp decline in drinking water. In fact, there are already reports of drinking water problems in this region.

Loss of Himalayan glaciers could also cause large-scale impact on the economy and food security as the northern region sustains so much agriculture, infrastructure and tourism.

Recommendations

The report provided recommendations on how to deal with extreme conditions, although the earth has gone past the tipping point of reversal.

Sustainable farming and fishing is recommended, along with a change in diet and adoption of indigenous knowledge of conservancy, the report stated. It also stressed on disaster infrastructure and the need to have early warning systems for extreme weather events.


Also read: Don’t bet on the UN to fix climate change – it’s failed for 30 years


 

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