8 months ago

Warmer seas pose bigger threat to life

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Senior citizens often express their worries over the changes in the timing and nature of seasonal events such as late arrival of the winter, its shorter span or absence of rain in the rainy season. But people want to reassure themselves with the hope that it might be an exceptional season and things will return to normal again.

But the recent developments have shattered such hopes. The changes are actually becoming permanent. The summers are getting longer and prolonged heatwaves, a new phenomenon, are now visiting us more frequently than before. Consider the rainy season comprising the Bengali months of Ashar and Shraban, which span the months of June-July and July-August on the Gregorian calendar. Ashar (June-July) comes with heavy rains, while Shraban (July-August) is known for its frequent spells of rain and sun every day, all over the month. But rain is getting rarer in the monsoon. Last year's was the driest ever Shraban in the last four decades with record low rainfall. According to the Bangladesh Meteorological Department (BMD), the country's highest rainfall at an average of 523 millimetres is recorded in the month of July. In June it is 460 millimetres on an average. But 2022's July saw 58 per cent less rainfall, which is slightly over one third of the normal rainfall. This July (of 2023), too, was not much different from last year's with slightly over 50 per cent (51 per cent, to be exact) rainfall.  Bangladesh also experienced an extremely hot July this year. So it did during April, May and June. But Bangladesh alone was not suffering from the searing heatwaves. In fact, the entire world has been exposed to this strange behaviour of nature. Scientists believe, it is the oceans' surface that has become very hot. European Union climate observatory data show that last week on July 30, ocean surface temperature reached 20.96 degrees Celsius. But July is not the month when the ocean should be, going by the records, so hot. If at all, it should be in March. 

Dr Samantha Burgess of the Copernicus Climate Change Service (C3S) from the European Union (EU) is also of the view that March, not August, should be the time when ocean surface is the warmest globally. So, what is concerning about the development is if the ocean temperature would break previous record next March.For in March 2016, the ocean temperature was 20.95 degrees Celsius. But it was the time when El Nino, a climate pattern characterised by unusual warming of the surface waters in the eastern tropical Pacific Ocean, was in full swing. In fact, it is part of a bigger oceanic phenomenon called 'El Nino Southern Oscillation (ENSO). During the El Nino phase of the ENSO, the surface temperature of the eastern tropical Pacific Ocean rises unusually. Similarly, there is an opposite phase of ENSO, called La Nina when that region of the ocean is marked by unusual cooling of the ocean's surface water. Episodes of both El Nino and La Nina have widespread impacts on global weather patterns accompanied by extreme heatwaves, wild fires, excessive rainfall, hurricanes and so on. Such states of climate pattern caused by the ocean can last nine to twelve months. Sometimes, it can even continue for years. Now the question that is worrying climate scientists is if the very high ocean temperature recorded on July 30 that broke 2016's El Nino record was exceptional or a new normal? Or was it global warming at work?  The answers to these questions are crucial to the scientists' understanding of the erratic behaviour of weather patterns across the globe.

Now, why should it bother scientists at all? In fact, oceans are a climate regulator as they soak up 90 per cent of the excess heat humans have been producing through their activities like fossil fuel burning and destruction of forests. An ocean not only absorbs heat, but also acts as the biggest carbon sink (absorbs CO2, the greenhouse gas) and produce half of the world's oxygen.  But warmer oceans are less capable of absorbing CO2. That is yet another piece of bad news for humanity because with oceans getting warmer, more CO2 will remain in the atmosphere meaning it will accelerate the process of global warming further.As it has already been happening, glaciers will melt faster raising the sea level threatening coastal populations everywhere. 

Temperatures in the seas have been rising since at least 1980s. But lately, the impact of La Nina (the cooler phase of ENSO) had been holding the rise (of temperatures) in check.  Now, maybe, El Nino has been driving up the sea temperatures further. The trajectory for ocean surface temperatures has been described by climate scientists as 'headed off the charts', according to the British daily newspaper, Guardian. What can be its other possible impacts rather than the heatwaves, droughts, hurricanes or downpours on the land? Heated up seas may force marine species like fishes and whales to move to cooler regions thereby disturbing the food chain. This may affect fish stocks. Dr Kathryn Lesneski, who according to the BBC, is monitoring a marine heatwave in the Gulf of Mexico for the National Oceanic and Atmospheric Administration (NOAA) said there was widespread coral bleaching at shallow reefs in Florida and many corals have already died, she added. Corals are mostly organisms that make colonies of hundreds of thousands of individual animals called polyps. Their colonies are like tropical forests of the oceans providing food, shelter and spawning ground to sea creatures. So, their destruction will be to the marine life like what deforestation is to humans and other animals on land. 

These are all bad news for humanity, indeed, all forms of life on Earth.


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