Source: BBC
As scientists announce new record ocean temperatures in April this year, a new study has highlighted the extent of the problem: The planet has accumulated almost as much heat in the past 15 years as it did over the previous 45 years, and the vast majority of that extra energy has gone into the oceans.
Data from the National Oceanic and Atmospheric Administration (NOAA) showed the average temperature at the ocean’s surface hit 21.1°C at the start of April—beating the previous high set in 2016 of 21°C. Even more worryingly, while global sea surface temperature has increased by a fraction of a degree, regional warming has, in some cases, been extreme: In March, sea surface temperatures off North America’s east coast were as much as 13.8°C higher than the 1981–2011 average.
Why such rapid changes are happening isn’t fully understood, but scientists agree that the El Niño–Southern Oscillation (ENSO)—the cycle of warm and cold sea surface temperature of the tropical Pacific Ocean—is playing a profound role. Three years of La Niña—the cool phase—across the tropical Pacific have suppressed temperatures, dampening the warming effect of rising greenhouse gas emissions. But researchers believe the “triple dip” La Niña is coming to an end, and a strong El Niño weather event will set in over the coming months.
While air temperatures have risen by more than 1.5°C compared to preindustrial times, the ocean surface temperature has increased by a smaller amount, around 0.9°C since preindustrial levels. However, the consequences are dire: species loss due to frequent and more prolonged marine heatwaves, more-dangerous hurricanes and cyclones, and more-severe coastal flooding due to sea level rise. As greenhouse gas emissions continue to rise, it seems these are grim realities we’ll have to get used to.
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