Over the past few weeks, global ocean temperatures have risen sharply, well above record levels. Scientists are trying to figure out what that means and whether it predicts a surge in atmospheric warming.
Some researchers attribute the surge in sea surface temperature to the emergence of a natural El Niño event and possibly strong natural warming weather conditions, as well as recovery from three years of La Niña cooling. increase. If so, this month’s record-breaking sea temperature could be the first of many thermal records to be shattered, they said.
According to the University of Maine’s Climate Reanalyzer, used and trusted by climate scientists, global average sea surface temperature has risen by nearly two tenths of a degree Celsius since early March this week. It may sound small, but considering that the global ocean average, which covers 71% of the Earth’s area, has risen so much in such a short period of time, “it’s huge,” said a climate scientist at the University of Colorado. One Chris Karnauskas said: “This is an incredible departure from what was originally warm.”
Climate scientists discuss warming on social media and among themselves. Some, like Michael Mann of the University of Pennsylvania, are quick to dismiss concerns, saying that El Niño is only expanding on top of the steady increase in human-caused warming.
In particular, it is warming off the coast of Peru and Ecuador, where most El Niños started before the 1980s. El Niño is a naturally occurring warming event in parts of the equatorial Pacific that alters weather around the world and causes global temperatures to soar. Until last month, the world was on the other side, with an unusually strong and prolonged cooling called La Niña, causing extreme weather for three years.
Other climate scientists, including oceanographer Gregory C. Johnson of the National Oceanic and Atmospheric Administration, say El Niño doesn’t seem to be the only one. He said there are some marine heatwaves or spots of ocean warming that don’t fit the El Niño pattern, such as the North Pacific near Alaska and off Spain.
“This is an unusual pattern,” said Gabe Vecki, a climate scientist at Princeton University. It’s a signal, and I think it takes some effort to understand it.”
The University of Colorado at Karnauskas took global sea surface temperature outliers from the past few weeks and subtracted the average temperature outliers from the beginning of the year to identify where the most rapid warming has occurred. He found that a long stretch across the equator from South America to Africa, including both the Pacific and Indian Oceans, is responsible for much of the global warming.
Karnauskas said the area warmed by 0.4 degrees Celsius in just 10 to 14 days, which is very unusual.
Part of the region is clearly an El Niño outbreak, and scientists may see an El Niño in the coming months and see it intensify, Karnauskas said. However, the area of the Indian Ocean is different and could be an accidental independent increase or somehow related to a large El Niño.
“We are already starting with such a high background condition, a very high baseline sea temperature across the globe, including the tropical Pacific and Indian Oceans. It seems to be off the charts now,” Karnauskas said.
About seven years have passed since the last El Nino. Scripps Institution of Oceanography oceanographer Sarah Perkey says the world has warmed over the past seven years, with deep oceans in particular absorbing most of the thermal energy from greenhouse gases. Ocean heat, which measures the energy stored in the deep ocean, is setting new records every year, regardless of what’s happening at the surface.
Global heat has increased by 0.04 degrees Celsius (0.07 degrees Fahrenheit) since the last El Niño. This may not sound like much, but “it’s actually a tremendous amount of energy,” Perkey said. That’s about 30 to 40 zettajoules of heat, the energy equivalent of the hundreds of millions of atomic bombs that destroyed Hiroshima, she said.
In addition to deep-sea warming, the world experienced unusual surface cooling in the three years following La Niña, acting like a lid for a warming pot, scientists say. Its lid is off.
“The temporary hold on global warming due to La Niña has been lifted,” NOAA oceanographer Mike McFadden said in an email. “One of the results he has is that March 2023 was his second-highest March on record for global mean surface temperature.”
If El Niño is expected to emerge later this year, “what we’re seeing now is just a prelude to more records in the pipeline,” McFadden wrote.
Karnauskas said warming is likely to “accelerate” after the heat has been hidden for several years.
© 2023 The Canadian Press
