Global average temperatures last year were tied for the hottest on record, capping what was also the planet's hottest decade ever recorded, according to new data analysis released Friday.
The last six years are now the hottest six on record, with 2020 on par with 2016 as the hottest year ever recorded.
The new analysis comes from the European Union's Copernicus Climate Change Service, one of several datasets which track global temperatures and climate change impacts.
Last year's temperatures were 0.6 degrees Celsius (1.08 degrees Fahrenheit) warmer than the 1981 to 2010 average, and 1.25 degrees Celsius (2.25 degrees Fahrenheit) above the pre-industrial average.
Global warming has brought the planet ever closer to the 1.5 degree Celsius warming threshold, which scientists have warned will increase the risk for more extreme wildfires, droughts, floods and food shortages potentially impacting hundreds of millions of people.
However, it was abundantly clear in 2020 that the world is already seeing worsening disasters from climate change.
It began in January, when heat and drought stoked unprecedented wildfires across Australia. When the flames were finally extinguished, the fires had charred an area larger than the state of Florida. An analysis last year found that climate change made the fires at least 30% more likely.
Then came the Atlantic hurricane season, which saw a record-breaking 30 named storms, 12 of which made landfall in the US. Many of those storms carried the fingerprints of climate change, which scientists say is making hurricanes more destructive.
Extremely hot and dry conditions also fueled the worst wildfire season ever recorded in the Western US, which engulfed an estimated 10.3 million acres in flames.
And in the Arctic, some of the most extreme temperatures anywhere on Earth were observed in 2020, as the region continues to warm more than twice as fast as the rest of the planet.
Huge parts of the Arctic saw temperatures more than 3 degrees Celsius (5.4 degrees Fahrenheit) above average, and some locations saw average temperatures more than 6 degrees Celsius (10.8 degrees Fahrenheit) above normal for the year.
To illustrate how enormous a 6 degree Celsius difference can be -- during the last ice age, which occurred around 20,000 years ago and featured much of North America covered in ice, the planet's average temperature was about 6 degrees Celsius cooler than it is today.
"2020 stands out for its exceptional warmth in the Arctic and a record number of tropical storms in the North Atlantic," said Carlo Buontempo, the director of the Copernicus Climate Change Service, in a news release. "It is no surprise that the last decade was the warmest on record, and is yet another reminder of the urgency of ambitious emissions reductions to prevent adverse climate impacts in the future."
La Niña fails to cool the planet down
Making the heat in 2020 all the more startling is the fact that the year featured La Niña, a naturally occurring climate cycle characterized by cooler than normal temperatures in the Pacific Ocean. The large expanse of cooler ocean water and the resulting impacts on the global climate act like a natural air conditioner for the planet, and La Niña years tend to make the planet cooler than years without a La Niña or the opposite phase of the cycle, called El Niño.
El Niño, which features warmer than average ocean temperatures in the Pacific, adds large amounts of excess heat released into the atmosphere and tends to make those years warmer.
It is no surprise that 2016, which had previously been the hottest year on record, featured a strong El Niño for the first half of the year. It is remarkable, however, that even with the cooling effects of La Niña present, that 2020 would feature the same amount of global heat.
This provides yet another yardstick to measure the impact that human-caused global warming is having on the planet's climate.
Greenhouse gas levels rise despite COVID-19 lockdowns
2020 set another record according to Copernicus Climate Change Service, with carbon dioxide concentrations reaching a maximum of 413 parts per million (ppm) during May.
It may seem counterintuitive that a year dominated by Covid-related shutdowns and a halt to global production and transportation would have the highest CO2 levels of any on record. But the fact is that until fossil fuel production reaches net-zero, or carbon dioxide is removed from the atmosphere on a major, globally-coordinated scale, each year will likely see higher carbon dioxide levels than the last.
The increase in atmospheric CO2 concentration in 2020 was slightly less than what was seen in each of the past two years (2.3 ppm vs 2.5 and 2.4 in 2019 and 2018, respectively).
This could partly be the result of Covid-related shutdowns, which some estimates show reduced human CO2 emissions in 2020 by around 7%, according to the Global Carbon Project. However, more research is needed to determine exactly how big of a role the pandemic played in cutting emissions last year.