Even if we meet our most ambitious climate goal — keeping global temperatures within a strict 1.5 degrees Celsius (or 2.7 degree Fahrenheit) of their preindustrial levels — there will still be consequences, scientists say. And they’ll last for years after we stop emitting carbon dioxide into the atmosphere.
New research suggests that extreme El Niño events — which can cause intense rainfall, flooding and other severe weather events in certain parts of the world — will occur more and more often as long as humans continue producing greenhouse gas emissions. And even if we’re able to stabilize the global climate at the 1.5-degree threshold, the study concludes, these events will continue to increase in frequency for up to another 100 years afterward. The findings were published Monday in the journal Nature Climate Change.
“It was really a surprise that what we find is after we reach 1.5 degrees Celsius and stabilize world temperatures, the frequency of extreme El Niño continued to increase for another century,” said Wenju Cai, a chief research scientist at Australia’s Commonwealth Scientific and Industrial Research Organization and one of the study’s lead authors. “We were expecting that the risk would stabilize.”
The study builds on a 2014 paper, also published in Nature Climate Change by Cai and a group of colleagues, which first suggested that extreme El Niño events will increase with global warming. That paper focused on a business-as-usual climate trajectory, in which greenhouse gas emissions remain at high levels into the future, Cai noted. It found that under this scenario, the frequency of extreme El Niño events would double from their preindustrial levels within this century.
The 2014 paper produced mixed responses among scientists at the time. Some experts, including Kevin Trenberth of the National Center for Atmospheric Research, suggested the models they used may not accurately simulate the behavior of El Niño.
Nevertheless, after the Paris climate agreement was finalized, and the 1.5-degree temperature goal was established, the researchers were interested in revisiting their previous work. This time, they specifically investigated the way El Niño would be affected if the world actually managed to stay within this climate threshold, a target that many scientists believe is already close to slipping through our fingers. Recent research has suggested that we’re on track to overshoot this climate goal within the next few decades.