In a time of climate anxiety, 2019 was the second-warmest year since scientists began taking temperatures in 1880, government scientists announced Wednesday.
The near-record temperatures cemented the last decade’s title as the warmest in modern human history, according to data from NASA and the National Oceanic and Atmospheric Administration. Each of the last five years was among the five warmest years on record, NASA said.
The steady increase in land and ocean temperatures around the world has been fueled by greenhouse gas emissions since the onset of the Industrial Revolution.
“The last decade is the warmest decade,” Gavin Schmidt, director of NASA’s Goddard Institute for Space Studies in New York, said at the American Meteorological Society’s annual meeting in Boston.
“Every decade since the 1960s has been warmer than the decade previously — and not by a small amount,” he added.
This warming trend probably won’t be slowing down anytime soon, said Derek Arndt, chief of climate monitoring for NOAA’s National Centers for Environmental Information in Asheville, N.C.
“Notwithstanding some sort of major, major geophysical event, it would be almost certain that the [coming] decade will be warmer than the previous,” he said at the meteorological society meeting. And, he said, it’s “almost certain that we will break at least one annual record.”
In 2019, the average global surface temperature was 1.71 degrees above the 20th century average of 57 degrees Fahrenheit, according to NOAA’s measurements. That was just 0.07 of a degree shy of the 1.78-degree record set in 2016.
NASA pegged 2019’s global temperature at 1.77 degrees Fahrenheit above the average from 1951 to 1980, within spitting distance of 2016’s record-setting anomaly of 1.83 degrees.
Each agency performs its own analysis using temperature readings from thousands of land-based weather stations around the world as well as from buoys floating throughout the oceans. Minor differences in their methods produce slight variations in the numbers, but the results are in lockstep when it comes to the pace and direction of global warming.
The last five years were all exceptionally warm, with only small differences that were driven by natural variations in weather patterns, scientists said.
“We’ve seen very clearly over the long term [with] many decades of temperature observations from around the world that the global temperature is going up,” said Noah Diffenbaugh, a climate scientist at Stanford University who was not involved in the analyses.
Periodic climate patterns may play a small role in driving temperatures upward or downward, Schmidt said. For example, 2016 clinched the title with a small nudge from El Niño warming.
If the effects from El Niño and La Niña were removed, the ranking of the warmest years might shift slightly — 2017 would have taken top spot, with 2016 demoted to second place and 2019 taking third. But the overall warming trend still continues unabated, Schmidt said.
Diffenbaugh concurred. “The signal of that warming is very strong compared to the year-to-year and decade-to-decade fluctuations that occur as a result of the variability in the ocean and atmosphere,” he said.
Earth’s climate has experienced natural variation over long time scales, but the speed and ferocity of global warming since the 19th century have been anything but natural, researchers said.
Benjamin Santer, an atmospheric scientist at Lawrence Livermore National Laboratory, said researchers have gone to great lengths to tease out how various natural phenomena leave their mark on the planet’s climate dynamics.
“And the message from that climate fingerprinting, from the pattern analysis, is nature couldn’t do this,” Santer said. “No combination of natural cycles, changes in the sun’s energy output, recovery from volcanic eruptions, could generate the observed changes.”
Global warming’s onslaught on the higher latitudes continued unabated this year, with continued ice mass losses in Greenland and Antarctica. The Arctic has warmed a little over three times faster than the rest of the world since 1970, officials said. Annual sea ice extent dipped to its second-lowest levels in both the Arctic (about 3.94 million square miles) and the Antarctic (4.16 million square miles).
Alaska saw its warmest year on record, with an average annual temperature of 32.2 degrees Fahrenheit. That was 6.2 degrees above the 1925-2000 average, scientists said.
Earth’s increasing surface temperature has probably played a role in the growth of certain extreme weather events — both in number and intensity. For example, scientists say warming has led to drier conditions in some areas, potentially worsening droughts or raising the risk of wildfire. Higher temperatures have caused sea levels to rise, making dangerous storm surges more likely and prompting hurricanes to dump more rain.
According to NOAA’s National Centers for Environmental Information, in 2019 there were 14 weather and climate disaster events in the United States with losses that each topped the $1-billion mark. That made it the fifth consecutive year with 10 or more billion-dollar weather or climate disasters. (Between 1980 and 2019, the average number of such events was 6.5 per year; in the last five years, that figure has shot up to 13.8.)
These natural disasters included flooding, severe storms, tropical cyclones and wildfires. The Californian and Alaskan wildfires that burned during the summer and fall last year caused an estimated $4.5 billion in losses. Major flood events generated $20 billion in damages, and severe storms left a nearly $14-billion bill in their wake. Altogether, the 14 events resulted in $45 billion in losses and 44 deaths, NOAA found.
Meanwhile, President Trump made good on a campaign promise by initiating the United States’ formal withdrawal from the Paris climate agreement. The international accord aims to reduce greenhouse gas emissions and limit global warming to “well below” 2 degrees Celsius (or 3.6 degrees Fahrenheit) above preindustrial levels, and to aim for a limit of 1.5 degrees Celsius.
The NASA and NOAA measurements indicate that limit is quickly approaching, Schmidt said.
“It’s the first decade that is clearly 1 degree Celsius above the late 19th century that we’ve had,” he said.
Warming since the 1970s has been relatively linear, Schmidt observed. If that trend continues, Earth could potentially cross the 1.5-degree mark for the first time around 2035 — though it could zigzag back and forth over that threshold before firmly climbing onward.
“But of course, that depends on what we do with emissions, and we aren’t able to tell you by looking at the past how society will actually react to this information,” he said.
The year 2019 ended with major wildfires flaring in eastern Australia while firefighters continued to battle blazes in California. The dueling fire seasons offered one example of how climate change might put a strain on humans’ ability to deal with natural disasters.
Since California and Australia are in different hemispheres, their fire seasons have been staggered, allowing them to share firefighting personnel and other resources. But if increasingly warm and dry conditions lead to an overlap in global fire seasons, those resources could become increasingly strained, Diffenbaugh said.
“When the climate events fall outside of the historical envelope of what our systems are designed around, then that’s really where we see the most acute pressures,” he said.