Andrea Thompson in Scientific American:
2016 was the hottest year in 137 years of record keeping and the third year in a row to take the number one slot, a mark of how much the world has warmed over the last century because of human activities, U.S. government scientists announced Wednesday.
2016 is a “data point at the end of many data points that indicates” long-term warming, Deke Arndt, chief of the monitoring branch of the National Centers for Environmental Information, said.
While the record was expected, the joint announcement by NASA and the National Oceanic and Atmospheric Administration came in the midst of Senate confirmation hearings for President-elect Trump’s cabinet nominees, several of whom have expressed doubts about established climate science, as has Trump himself.
Many climate scientists, policy experts and environmentalists are concerned about the potential for the incoming administration to limit funding for climate science and roll back both national and international progress toward limiting the greenhouse gases that are warming the planet.
According to NOAA data, the global average temperature for 2016 was 1.69°F (0.94°C) above the 20th century average and 0.07°F (0.04°C) above the previous record set last year.
In NASA’s records, 2016 was 1.8°F (0.99°C) above the 1951-1980 average.
Each agency has slightly different methods of processing the data and different baseline periods they use for comparison, as do other groups around the world that monitor global temperatures, leading to slightly different year-to-year numbers.
But despite these differences, all of these records “are capturing the same long-term signal. It’s a pretty unmistakable signal,” Arndt said. Or as he likes to put it: “They’re singing the same song, even if they’re hitting different notes along the way.”