Scientists from two government agencies confirmed on Wednesday that average global temperatures in 2015 were the highest in 136 years of record keeping, and the world is likely to see more of the same in 2016.
The reason, emphasized NASA climate scientist Gavin Schmidt, is that excess carbon dioxide, created by deforestation and burning fossil fuels for energy, is trapping heat in the atmosphere.
“The trend over time is why we’re having a record warm year,” Schmidt, the director of NASA’s Goddard Institute for Space Studies, told reporters on Wednesday. “There is no indication that that trend has slowed, paused, or ‘hiatused’ in the past few decades.”
Most of the resulting warming has happened over the past 35 years, and 15 of the 16 hottest years on record have occurred since 2001, according to NASA.
Combined, the globe’s average ocean and land surface temperatures in 2015 were 1.62 degrees Fahrenheit above the 20th-century average and a quarter of a degree Fahrenheit warmer than in 2014, said Thomas R. Karl, the director of the National Oceanic and Atmospheric Administration’s National Centers for Environmental Information.
It was the largest year-on-year increase in record-breaking global temperatures, he said.
Both Schmidt and Karl emphasized that rising greenhouse gas emissions are responsible for record temperatures, independent of weather cycles such as the current warming trend in the central Pacific.
“The interesting thing is that 2015 did not start with an El Niño event in the tropical Pacific,” said Schmidt, but still showed unusually high temperatures early on. “Even without El Niño, this would have been the warmest year on record.”
Once the El Niño cycle began to affect temperatures after midyear, “October, November, and December were record warm anomalies for any month in the record,” he added.
Schmidt underscored that while climate change can’t be linked to every extreme weather event, it has been firmly linked to severe heat waves, loss of Arctic sea ice, rising sea levels, and the melting of glaciers around the world. “We’ll expect that to continue into 2016,” he said, “as global warming continues.”
Now that a particularly strong El Niño-based warming– trend is under way, Schmidt and Karl said, scientists believe it could combine with 2015’s high sea surface temperatures to make 2016 another record-breaking hot year.
If that happens, it will be the first time in the 136-year record that three record-breaking hot years have occurred in a row.
Last year marked the first time in history that average land and sea surface temperatures surged 1.8 degrees Fahrenheit, or one full degree Celsius, beyond those of the 19th century, according to the NASA and NOAA analyses.
World leaders agreed in December in Paris to keep temperature rise to 2 degrees Celsius.
“What we’re going to see are more and clearer impacts as the climate warms,” said Schmidt. “We’re on a trajectory that, because the carbon cycle is very out of balance right now, can’t be turned around easily.”
While some climate research suggests that an 80 percent cut in carbon emissions between now and 2050 could stabilize the climate, there’s no evidence to date that the world as a whole can find the will to make that happen, Schmidt noted. It is up to “society and policy makers,” he added, “to decide what to do with that information.”