The year 2020 tied with 2016 for the planet’s warmest on record, capping off the warmest decade ever observed, according to new data released Friday by the Copernicus Climate Change Service, a program of the European Commission.

Each of past six years has been hotter than all of the years before 2015 in a temperature record that dates back to the late-19th century, Copernicus reported. Globally, 2020 was 1.08 degrees (0.6 Celsius) warmer than the 1981-2010 average and about 2.25 degrees (1.25 Celsius) above the 1850-1900 preindustrial period.

The climate agency released its year-end numbers Friday ahead of NASA, the National Oceanic and Atmospheric Administration and Berkeley Earth, which will weigh in on Jan. 14. They are expected to rank the year as either the first or second-warmest on record, due to slightly different ways of measuring global temperatures.

In the Copernicus data, 2020 would have held the No. 1 ranking by itself if it weren’t for a slightly cool December, relative to the rest of the year. To climate scientists, this is alarming, because 2016′s record was aided by a largely natural climate cyclone known as El Niño, which features above-average sea surface temperatures across the tropical Pacific Ocean near the equator.

An unusually intense El Niño event occurred in 2016, adding more heat to the atmosphere and changing global weather patterns. But instead of El Niño being present this year, the phenomenon’s colder sibling, La Niña, took hold in the tropical Pacific.

Characterized by cooler-than-average ocean temperatures, La Niña years tend not to set global, all-time high temperature records.

If one pictures global warming as a car rolling down a hill, El Niño acts as a gas pedal, speeding the descent, whereas La Niña serves as a modest application of the brakes.

What’s happening now, scientists say, is that even La Niña years are setting global temperature records, due to the overpowering influence of human-caused warming from decades of greenhouse gas emissions. It’s as if the climate system reached for the brake and found it doesn’t work, so the car kept accelerating down the hill.

“I’m not surprised that 2020 was yet another record-setting year — these record years are just going to continue,” said Sue Natali, a climate researcher who directs the Arctic program at the Woodwell Climate Research Center in Massachusetts. “I’m not sure how extreme things have to get for the message to get across that we’re heading into a climate emergency unless we take some ambitious and immediate action to control global climate change.”

With more greenhouse gases in the air each year — atmospheric concentrations hit a record high of 413 parts per million in 2020, according to Copernicus, each La Niña year will probably be warmer than the last, and each El Niño event is likely to set a record as well.

“2020 stands out for its exceptional warmth in the Arctic and a record number of tropical storms in the North Atlantic,” said Copernicus Director Carlo Buontempo, in a statement. “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.”

Global records came amid relentless disasters

Some of 2020′s most extreme climate conditions were focused in northern Siberia and parts of the Arctic with annual average temperatures that were between 5.4 to 10.8 degrees (3 to 6 Celsius) above normal. In certain months, these anomalies topped 14.4 degrees (8 Celsius). Even after a somewhat cooler December compared to prior months, Siberia stands out on Copernicus’s map as a large red splotch of unusual mildness.

The warmer-than-usual conditions there had major consequences. Wildfires in the Siberian Arctic began early, in May, and continued through October. These blazes set a record for the amount of carbon dioxide released from wildfires north of the Arctic Circle, according to the Copernicus Atmosphere Monitoring Service.

During one extreme heat wave, the mercury climbed to 100.4 degrees Fahrenheit (38 Celsius) on June 20 in the remote Siberian town of Verkhoyansk, about 3,000 miles east of Moscow. This is the highest temperature in the Arctic since record-keeping began in 1885.

These conditions also may have destabilized vast areas of previously frozen ground known as permafrost, emitting carbon dioxide, methane and other global warming gases. In Siberia, massive holes in the ground, looking like sunken craters on other planets, have opened in recent years as the permafrost has thawed.

“We often talk about global temperature increase in terms of average temperature change, but we know it’s not only the average that’s important,” said Natali, a permafrost expert, in an email.

“These record-setting years and record-setting months can have a disproportionate impact due to the occurrence of extreme events and disturbances, such as abrupt permafrost thaw and wildfires, that have long-lasting impacts on the landscape and on carbon emissions.”

A study released by the World Weather Attribution project concluded that the record Arctic heat from January through June was nearly impossible in the absence of global warming, with the odds of such an outcome made 600 times more likely by human-caused climate change.

Last year was marked by a merciless parade of devastating extreme weather disasters, some of them long predicted by climate scientists but occurring earlier and with greater ferocity than expected. The year started with deadly wildfires in Australia that scorched some of the country’s most biologically rich ecosystems, killing or harming nearly 3 billion animals.

It featured the busiest Atlantic hurricane season on record, with the most named storms to make landfall in a single season in U.S. history.

According to Munich Re, losses from natural disasters in 2020 came to $210 billion, which the reinsurance giant tied in part to global warming. A deadly, unusually widespread and record-shattering wildfire season in the West led to $16 billion in losses, Munich Re found in a report issued Thursday. It was California’s worst fire season on record, with five of the top six largest wildfires in state history occurring this year.

At one point, fires burned from Washington state to Southern California and east to Colorado, smothering the region in noxious smoke. Studies have linked the increase in large and intense Western blazes to climate change, which is leading to an uptick in the occurrence of extreme fire weather.