NASA declared Wednesday that 2018 was the fourth-hottest year in 139 years of records as average global temperatures rose alongside surging fossil fuel emissions.
The annual analysis released by NASA and the National Oceanic and Atmospheric Administration found average temperatures across land and sea surfaces 1.42 degrees Fahrenheit above the 20th-century average, putting 2018 fourth, behind 2016, 2015 and 2017.
Last December was the second-warmest December in the 139 years that records have been kept.
“The last five years are the five warmest years on record,” said Deke Arndt, the chief of climate monitoring at NOAA’s National Centers for Environmental Information in Asheville, North Carolina. “The last four years are clearly the four warmest years on record.”
He said the warming trend “very much resembles riding up an escalator over time” and compared the year-to-year differences to “jumping up and down while you’re on that escalator.”
El Niño, the Pacific Ocean pattern that can cause record-setting warm weather, intensified warming during some of the past five years and might “mean 2019 could be warmer than 2018,” said Gavin Schmidt, the director of NASA’s Goddard Institute for Space Studies.
Evidence of that warming can be seen around the world as a record-breaking heat wave roasts Australia and warming oceans in the Arctic loose frigid polar winds on huge swaths of North America. The agencies calculated $91 billion in damage from last year’s hurricanes and wildfires across the United States.
“2018 was an exclamation point,” Arndt said.
A loss of sea ice in the Arctic may be the most dramatic sign of the temperature rise. In December, NOAA’s annual report on the Arctic found that the region had its second-lowest overall sea-ice coverage on record. That loss is most pronounced in the summer, but Schmidt warned Wednesday that there are “decreases in the winter as well.”
“We obviously are very concerned about what’s going on in the Arctic,” he said.
Greenhouse gas emissions are the indisputable cause of warming, but the temperature increases seen in the past year are indicative of past decades of burning fossil fuels.
“We still collectively have our foot on the accelerator, and while there are some indications in some parts of the world that people are working quite hard to reduce those emissions, collectively we are not doing so,” Schmidt said. “The year-by-year changes are not that important.”
But the signs are not looking good. Global carbon dioxide emissions surged for the second year in a row, hitting a record high in 2018. The United States’ emissions spiked 3.4 percent last year from the year before, the second-largest annual increase in more than two decades, a report from the economic research firm Rhodium Group found in December.
“2018 was an exclamation point.”
The trend is “being driven by these greenhouse gases,” Arndt said.
Currently, the Earth’s average temperature is more than 1 degree Celsius, (1.8 degrees Fahrenheit), above average temperatures in the late 1800s, when industrialized nations began burning huge amounts of coal and felling large areas of forest. The world is on a path to soon blow past the 2015 Paris Climate Agreement’s 2 degrees Celsius (3.6 degrees Fahrenheit) of warming, past which its predicted effects will be catastrophic.
There are some signs of hope for large-scale decarbonization. In the United States, by far the largest historic emitter of carbon dioxide, a new cadre of left-wing Democrats are pushing for a Green New Deal, a national industrial plan to rapidly scale down emissions over the next decade.
Yet the issue remains hotly politicized in the United States. On Tuesday night, President Donald Trump, who routinely dismisses and mocks climate science, made no mention of the crisis in his State of the Union address. The Democratic response referred to climate change only in passing, but the Democratic-controlled House held two hearings on Wednesday morning to investigate global warming.
Roughly 70 percent of Americans acknowledge global warming is happening, and 57 percent understand human activities are the primary cause, according to Yale University survey data. Yet the issue is only beginning to emerge as a high priority for voters. Ranking annual temperature records and extremes “is part of what people are interested in,” Schmidt said.
“While scientifically, we’re not totally excited by the rankings we talk about every year, people like that, it seems,” he said. “The key message here is the planet is warming.”