Sea surface temperatures set a new warm record in April and remain at near-record levels, worrying climate scientists who fear even warmer temperatures later in 2023 during an expected El Nino event in the Pacific Ocean.

The global average sea surface temperature – measured between 60 degrees south latitude and 60 degrees north latitude – reached a record high of 21.1 degrees C in early April, surpassing the record of 21 degrees C set in 2016, which was an El Nino year. It was also the highest since satellite measurements began.

The concern is that warmer oceans could trigger more extreme storms, accelerate the melting of glaciers and cause more severe heat waves that trigger mass coral bleaching.

The “rapid warming” of the sea is a reminder of the effects of climate change, climate scientists say.

– Large parts of the world’s oceans are warm. Unusual heat. The heat this year is likely to break all records, says Professor of Oceanography Moninya Roughan at the University of New South Wales (UNSW) in Sydney.

In an article in The Conversation on April 26, she explained that during La Nina, cooler water from the ocean depths rises to the surface and acts a bit like an air conditioner. El Nino is like turning off the air conditioner.

– When you run your air conditioner, you keep the heat out. It is the same for our oceans. La Nina led to three years of cooler conditions, while global warming continued at a rapid pace. Now we will probably see the heat return, she says.

It is the speed of the warming in recent weeks that has scientists both fascinated and worried.

This has scientists scratching their heads, said Professor Mike Meredith at the British Antarctic Survey to The Guardian at the end of April.

The fact that it is heating up as much as it has is a big surprise and very worrying. It can be a short-term extreme peak, or it can be the start of something much more serious.

“Daily global sea surface temperatures since April are really off the charts,” Dr Agus Santoso of the UNSW Climate Change Research Center told The Straits Times.

“This could be driven by global warming or very intense warming in certain places, or both, such as the warming off Peru that may eventually spread westward as part of a developing El Nino,” he said, pointing to intense warming of the ocean off parts of South America.

The global average sea surface temperature has dropped slightly to 20.9 degrees C on Tuesday, the latest data available, which is well above any other year in the past decade at this time of year. The data comes from the National Oceanic and Atmospheric Administration in the USA.

Although 0.1 degrees C or 0.2 degrees C may not sound like much, it takes a lot more energy to heat water than air, and as the oceans cover around 70 percent of the planet’s surface, there is a huge amount of heat that has been absorbed, the researchers explain.

Without the oceans, the planet would be much warmer, because the oceans have absorbed more than 90 percent of the excess heat caused by global warming, they continue.

A study published in January 2023 showed that 2022 was the warmest year on record in the world’s oceans.

Scientists’ biggest concern now is the impact of the next El Nino, which the UN said on Wednesday was increasingly likely to develop in the coming months, possibly leading to new heat records.

The World Meteorological Organization estimates that there is a 60 percent chance that El Nino will develop by the end of July, and an 80 percent chance that it will do so by the end of September. But how strong it will be is still unknown.

El Ninos affect weather systems worldwide and usually lead to warmer and drier conditions in Southeast Asia and Australia.

Professor Benjamin Horton, director of the Earth Observatory of Singapore at Nanyang Technological University, said the equatorial Indo-Pacific region is helping to drive the recent rise in sea surface temperatures.

Data from this region “clearly shows” that it is very likely that we will soon experience an El Nino, perhaps a very strong one, he told ST.

– If El Nino develops this year, it increases the chances of record hot global temperatures, he added.

During the 2016 El Nino, heatwaves made that year the hottest on record in Singapore, with an annual average temperature of 28.4 degrees.

Dry conditions also affected water supplies in some parts of the region and exacerbated forest fires in Indonesia that triggered widespread haze, and higher sea temperatures killed 15 percent to 20 percent of coral in Singapore, climate scientists say.

Dr. Santoso agrees that an El Nino in 2023 could lead to record temperatures.

After an El Nino, which is currently developing in the tropical Pacific, the global temperatures tend to rise, he said.

So if this El Nino appears later this year, the global sea surface temperatures towards the end of the year and especially in 2024 could be record high, especially if El Nino is strong, he concluded.