Although oceans and seas cover more than two-thirds of the Earth’s surface, they are taken for granted most of the time. We forget that they are rich in resources and provide us with food, energy and minerals, besides they are critical for stability of the planetary climate and local weather. Often lost in our misplaced imagery we have been thinking that the oceans were trivial component of the earth’s climate system, and that the consequences of change were minimal, due to our lack of adequate knowledge on the importance of marine ecosystem, for which we may have been forgiven until recently.
But not any longer, after the UN Intergovernmental Panel on Climate Change (IPCC), which evaluates the peer-reviewed scientific literature, in its major report revealed the important role the world’s oceans play in countering the worst effect of global warming that is triggering sweltering heat in summers, melting of glaciers, outbreak of wild fires and heat waves, etc, mainly caused by the carbon dioxide (Co2) released into the atmosphere due to indiscriminate burning of fossil fuels like coal and oil. Since industrialisation in the 19th century, the amount of this greenhouse gas in the earth’s atmosphere is said to have risen by as much as 40 per cent.
Researchers point out that if not for the oceans, temperatures would have been even higher than they are now, because they absorb a substantial amount of the carbon dioxide released into the air. When the concentration of carbon dioxide in the atmosphere rises, oceans absorb more to restore the balance. The colder the sea-water is, the more effectively the process works. It is thus important to remember that the ocean ecosystem regulates the global temperatures and atmospheric conditions, feed billions of people, and largely determines the weather. The ocean also has lot of ‘inertia’ – which means that getting the ocean to change takes a lot of energy, but once it begins to change, allowing it down becomes more or less impossible.
Recent study reports clearly explain the role oceans play in battling climate change. In the Labrador Sea and Greenland Sea as well as in regions under the Antarctic coast, large quantities of surface water sink into the deep sea where carbon dioxide is stored for a long time. The lion’s share of the stored greenhouse gas since the start of the Industrial Revolution will take centuries to return to the surface of the ocean again. Part of it will remain fixed in the sediment of the ocean floor. The Ocean does more than absorb a considerable amount of the greenhouse gas. It also soaks up nearly all the additional warmth resulting from the manmade greenhouse effect. That is how the oceans significantly slow down climate change.
Research studies have revealed that oceans have absorbed an astounding 95 per cent of the excess heat over the past 40 years. Increased atmospheric temperatures are attributable to just three per cent of this additional thermal energy and would be much greater if not for the oceans. The extra warmth is essentially hidden in the ocean, where it slowly spreads through the depths. Because of this, the surface temperature only increases at a snail’s pace.
All of this comes at a price. Absorbing excess carbon dioxide leads to a progressive acidification of the ocean water, while absorbing excess heat contributes to rising sea levels and troubling changes in the marine ecosystem. The warming of the oceans also contains dangerous feedback events. When the rate of evaporation on the ocean surface increases, it produces more water vapour – a potent greenhouse gas – which in turn causes temperatures to rise, and this results in the rate of evaporation to increase. These feedback events can accelerate global warming in ways that are difficult to predict, one more reason not to further burden the ocean ecosystem.
One of the most stunning conclusions from the IPCC’s report is the statement that ‘the current rate and magnitude of ocean acidification are at least 10 times faster than any event within the last 65 million years.” Given that periods of rapid acidification over tens of thousands of years – slow by our current human-driven standard – resulted in mass extinction and ecological collapse. According to IPCC’s report, due to unusual warming of oceans coupled with increasing ocean pollution and the consequent loss of biodiversity, the future of this unique ecosystem faces a grave threat today.
The increasing greenhouse gas concentrations in the atmosphere combined with a levelling off or decline in sulphate aerosols – which tend to offset the warming effects of greenhouse gas – will result in disruptive and unpredictable changes in global weather patterns during the next decades. Floods, droughts, outbreaks of wild fires and extreme heat waves, storms, etc, will likely become more frequent as atmospheric temperatures and warming of oceans increases. The IPCC has warned that the situation is disastrous as many of the benefits of our oceans (coral reefs, fisheries, coastal living, et al) would be transferred beyond recognition, if we fail to act on climate change decisively.
According to experts, failure to act on the climate change will see warmer and more stagnant oceans, with declining oxygen levels and productivity in some regions, and the removal or modification of ecosystem in many others. Fisheries and national economies are already in the crosshairs in many regions. Rising seas and intensifying storms, plus a loss of critical coastal features, will make life on the shores of rapidly changing oceans dangerously different to today. For this reason, meeting the goal of limiting global warming to two degrees Celsius agreed upon at the Paris Climate Conference is highly essential.
(The writer is a freelance journalist)
