Climate change: 2020 was world's equal-hottest year ever, despite La Niña

In 2020 it often felt like the world was on fire, and in at least one way it kind of was.

The year we'd all like to forget has just been named one of the hottest on record - at least top three, according to the World Meteorological Organization (WMO).

Its data shows 2020 ranks alongside 2016 and 2019, with the differences between them indistinguishably small. 

Every year since 2015 ranks among the hottest six ever, as the impacts of climate change continue to be felt.

2020 would have taken the title easily, WMO scientists said, if it weren't for the temporary cooling of the central Pacific Ocean - a regular process known as La Niña.

"The exceptional heat of 2020 is despite a La Niña event, which has a temporary cooling effect," said WMO Secretary-General Petteri Taalas. 

"It is remarkable that temperatures in 2020 were virtually on a par with 2016, when we saw one of the strongest El Niño warming events on record. This is a clear indication that the global signal from human-induced climate change is now as powerful as the force of nature."

In other words, while it wasn't any hotter than in 2016, that year had a distinct advantage and 2020 a disadvantage. 

La Niña is expected to strengthen in 2021, reducing its chances of topping 2020.  But the trend remains clear.

"The temperature ranking of individual years represent only a snapshot of a much longer-term trend," said Prof Taalas. "Since the 1980s each decade has been warmer than the previous one. Heat-trapping gases in the atmosphere remain at record levels and the long lifetime of carbon dioxide, the most important gas, commits the planet to future warming."

WMO uses data from several different sources around the world. NASA also concluded 2020 was equal-hottest with 2016, while the  National Oceanic and Atmospheric Administration placed it second behind 2016. 

The WMO said the differences between the three were in the margin of error. 

Earlier this week New Zealand's National Institute of Water and Atmospheric Research said it was our seventh-warmest year on record, with 2016 holding the dubious crown.

Also earlier this week Kiwi scientists said the world was approaching a tipping point - an average global temperature of 18C - which would see plants start to release more carbon dioxide than they take in. 

"In the past, all of our forests and grass have taken up carbon dioxide, offsetting some of the emissions that we have made into the atmosphere. That's been of great benefit for us - it's bought us some time," said study leader and professor of biogeochemistry at the University of Waikato, Louis Schipper.

"But what we have observed from this data is that the amount of carbon dioxide that's going to be taken up by these ecosystems is going to decline. We're going to have less time than perhaps we thought to reduce emissions into the atmosphere."