The past five years have been the warmest years since records began in the late 1800s, according to NASA and NOAA. On Wednesday it incorporated the final weeks of a year ago into its climate models and concluded that average global surface temperature in 2018 was 1 degree Celsius (1.8 Fahrenheit) above pre-industrial baseline levels. 2018 saw the 14th-highest mean temperature on record in the contiguous 48 states, and it was the third-wettest year for the area despite persistent drought in the southwest and the northern plains. It founds that 2018 global temperatures were 0.79 degrees Celsius above the 20th-century average.
That warming is driven by the amount of greenhouse gases humans have introduced into the atmosphere, particularly in the least 100 years, Schmidt said.
For years, climate change has been grossly ignored by President Trump, as well as Congress writ large. The quickly rising temperatures over the past two decades cap a much longer warming trend documented by researchers and correspond with the scientific consensus that climate change is caused by human activity.
NASA's temperature analyses incorporate surface temperature measurements from 6,300 weather stations, ship- and buoy-based observations of sea surface temperatures, and temperature measurements from Antarctic research stations. Much of Europe had its warmest years on record. Shown here are 2017 global temperature data from satellites.
It was also an expensive year for natural disasters. "2018 is yet again an extremely warm year on top of a long-term global warming trend".
"If there was no warming of average temperatures, there would be about an even chance of a daily record high maximum or daily record low minimum occurring", said Meehl, who was not involved in the report. That would be warmer than the last four years.
The NASA and NOAA reports are consistent with analyses by other governments, including the Japan Meteorological Agency and the European Union's Copernicus Climate Change Service, both of which also concluded that 2018 was the fourth-warmest year on record. It warned that intense heatwaves "are becoming more frequent as a result of climate change".
Dr. Schmidt spoke of these markers not as cliffs that the world would plunge over, however, but part of a continuing slide toward increasing levels of harm.