A sea of problems

While much of the discussions about global warming revolve around reducing emissions, the other half of the story — carbon sinks —is as important, if not more, for understanding the climate change challenge. A “carbon sink” is anything that absorbs more carbon than it releases into the atmosphere. Nature provides us with three — soil, forests and the oceans. Man-made or artificial carbon sinks also exist — deep underground natural formations or unused mines, which can be used to store carbon after capturing it, but currently the role these play is nowhere near as important as that played by forests and the oceans.

Current estimates suggest that forests absorb a third or more of the carbon emissions generated annually, though such calculations always depend on many assumptions. Leaders in every major country periodically announce plans to reduce deforestation/increase forest cover to help save the climate though not every country walks the talk. But the need for action on this front is slowly gathering steam across the world. At the recently held climate conference — COP 26 — in Glasgow, Scotland, more than 100 world leaders pledged at least $19 billion to protect and restore forests.

The oceans, though they cover 70 per cent of the earth’s surface, and are estimated to absorb a lot of the CO2 generated annually, have often been ignored in climate debates. That could be slowly changing now.

Before the era of industrialisation, the oceans actually released more carbon into the atmosphere than they took in. Over the past 200-odd years though, they have absorbed millions of tonnes of carbon emitted by factories, cars and other emission sources.

Again, how much CO2 and other greenhouse gases the oceans absorb every year is difficult to estimate. For a long time, climate scientists thought that the oceans absorbed roughly a quarter of the CO2 emissions generated every year by various sources. That could be a gross underestimate, say some researchers who have been studying carbon absorption patterns of the oceans. In 2020, two senior scientists from the University of Exeter pointed out that the surface of the ocean was quite a bit cooler than the water a few metres deep. As the water temperature affects its ability to absorb CO2, they estimate the oceans have been absorbing and storing a lot more of the gas than originally calculated. When the oceans warm up further, their ability to absorb CO2 will decrease too.

Other research also suggests that the temperature of water in many oceans also started rising much earlier than was estimated. Issues like the release of untreated sewage, plastic and other wastes into the ocean are also finally catching the eye of policymakers.

Why do the oceans matter so much? Simply because their “health” has major implications for marine ecology and also the land and population near the oceans. Climate researchers and policymakers are waking up to some of these only recently. Most discussions on global warming and the role of the oceans earlier focused only on the danger of rising water levels to low lying coastal areas, and not on the effects of climate change on marine ecosystems and food security of the population on many small Pacific islands.

Environmentalists have started talking about both the dangers of warming and of “ocean acidification” — a term that was rarely encountered even a decade ago.

Ocean acidification is a misnomer. The ph that is used to denote the acidity or alkalinity shows that the oceans still fall in the alkaline range. But the amount of carbon dioxide being absorbed by the oceans annually is slowly changing the ph values and they are becoming less alkaline. But ocean acidification is a catchier term and therefore better to use.

The problem with seas and oceans is that they have been understudied for years. Funding into research on all matters to do with the oceans was always an issue. So there are far too many things that we do not know, including the ecosystems in deep sea beds, how climate change is exactly affecting the behaviour of fish and aquatic mammals and even the growth of planktons and sea weeds, which are critical to the ecosystem.

But some of these things are now being studied and the findings are quite alarming. The changes in ocean temperatures and chemistry have already started affecting currents as well as marine life and behaviour. It has resulted in the destruction of corals as well as the loss of breeding ground for fish and mammals. Increased absorption of CO2 and oxygen depletion have also hastened evolution of species that now need to change to survive under new conditions. The ability of the oceans to act as a sink for gases and heat will also decrease with time.

Can anything be done before it is too late? Efforts are on at multiple levels. From better mapping of the oceans, collecting more data, exploring sea beds and studying behaviour of aquatic flora and fauna and work on technologies that can reverse or at least stop the oceans from changing further is going on. The flow of polluted water into the oceans is also being scrutinised and strategies are being developed for it.

All these need to expand. Climate change needs to be looked at in totality. For the earth to be saved, the oceans are as important as terra firma.