Climate Change News

Another Scorcher: 2019 Was the Second-Hottest Year on Record

Heat waves, massive melts, and droughts, oh my. The past decade was our hottest yet.

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Global average temperatures in 2019 soared above preindustrial temperatures, making it the second-hottest year on record as greenhouse gas emissions continue to warm the planet. The year was 1.15°C above the 1880–1900 average, second to only 2016.

NASA and the National Oceanographic and Atmospheric Administration (NOAA) released their annual summary yesterday based on temperatures taken from ocean sensors and more than 20,000 land-based weather stations. Independent analyses by the agencies both concluded that 2019 was nearly the hottest worldwide.

“We crossed over into more than 2° Fahrenheit (1.1°C) warming territory in 2015 and we are unlikely to go back,” said Gavin Schmidt of NASA. “This shows that what’s happening is persistent, not a fluke due to some weather phenomenon: We know that the long-term trends are being driven by the increasing levels of greenhouse gases in the atmosphere.”

The World Economic Forum’s annual risk report placed environmental issues in its top five for the first time. The list describes threats to “global prosperity” over the next 10 years, identifying risks such as recessions, cyberattacks, and political tensions. This year’s top five threats with the highest likelihood of occurring were all environmental in nature, including risks of extreme weather and biodiversity loss, which are both exacerbated by rising temperatures.

Although the year was the second hottest globally, it topped the charts in some locations, including the state of Alaska. Their annual temperatures were 3.5°C above the 1925–2000 average, making it the hottest on record. The Bering Sea on Alaska’s icy northwest coast was unusually bare for the majority of 2019, reported the New York Times.

Among other anomalies: Australia had its warmest year since records began in 1910, and hot, dry air led to the country’s worst-ever bushfire season. Cities in Europe broke records for all-time high temperature records, and one heat wave traveled over Greenland to create the largest ice melt recorded in one day.

The past 5 years have been the hottest since records began in 1880, and Schmidt said that the past decade was the first that stayed above the 1°C global average. The Paris Agreement aims to stop global climate warming at 1.5°C worldwide.

Schmidt guessed that global temperatures will pass 1.5°C by 2035, though global events could change that. “The warming until now, since the 1970s, has been quite close to linear,” he said. “But of course, that depends on what we do with emissions.”

Melting in the Arctic has been particularly stark in the past decade: Retreating snow caps in the Arctic are exposing soil that doesn’t contain radiocarbon, which means that soil hasn’t seen the Sun for at least 57,000 years, said Schmidt. The Arctic is warming 3 times as fast as the rest of the globe because of local feedback loops, like the water and land absorbing more heat as reflective ice melts away.

Scientists from two other international organizations, the World Meteorological Organization (WMO) and the United Kingdom’s Met Office, also released their global summary of 2019. WMO agreed with NASA and NOAA’s ranking, whereas the Met Office placed 2019 third. (The differences are largely due to how the calculations deal with limited data in the Arctic.)

What will the next decade bring? NOAA meteorologist Deke Arndt said that it is “almost certain” that the next decade will be warmer than the last and that there will be another record-breaking year in store. 2019 may not hold its title for long.

—Jenessa Duncombe (@jrdscience), News Writing and Production Fellow

Citation: Duncombe, J. (2020), Another scorcher: 2019 was the second-hottest year on record, Eos, 101, https://doi.org/10.1029/2020EO138771. Published on 16 January 2020.
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