New government data on temperatures around the world offers cold comfort to those who hope that global warming is on the wane. The data, released on Wednesday by NASA and the National Oceanic and Atmospheric Administration (NOAA), shows that 2018 was the fourth-hottest year since 1880, the earliest year for which reliable global temperature data is available.
The three hottest years on record were 2015, 2016 and 2017.
"In fact, the warmest five years in the record are just the last five years," Gavin Schmidt, director of NASA's Goddard Institute for Space Studies in New York City, and one of the experts who described the new data in a Wednesday morning press briefing, told NBC News MACH in an email before the event. "The long-term trends toward warmer temperatures are clear and continuing."
The average global surface temperature has risen about 2 degrees Fahrenheit (1 degree Celsius) since the 1880s, NASA data showed. NOAA, which uses different baselines and analyzes the data differently, found that global temperatures in 2018 were 1.42 degrees F (0.79 degrees C) above the 20th century average.
The new report makes it clear that "global warming shows no sign of slowing down or stopping," Kristina Dahl, a senior climate scientist at the Union of Concerned Scientists, said in an email.
Because weather patterns vary around the world, not every region experienced the same warming trend. Trends were strongest in the polar regions, which have seen continued loss of sea ice in the Arctic and shrinkage of the Greenland and Antarctic ice sheets.
In the contiguous U.S., 2018 was the 14th hottest year on record. Fourteen states had annual temperatures that were among the 10 highest on record. Arizona's temperatures in 2018 were the second highest on record, New Mexico's the third and California's fourth.
Rainfall also trended upward in 2018. NOAA data showed that the average precipitation in the contiguous U.S. was 34.63 inches, making it the wettest year in the past 35 years and the third-wettest since record-keeping began in 1895. While some parts of the country saw drier-than-normal years, nine eastern states — Delaware, Maryland, Massachusetts, New Jersey, North Carolina, Pennsylvania, Tennessee, Virginia and West Virginia — experienced their wettest years on record.
The temperature data was gathered by thousands of weather stations around the world and then analyzed to correct for any skewing of data that might be caused by the proximity of heat-producing urban areas or other conditions.
There's broad agreement among scientists that global warming is caused principally by human activity. In particular, the burning of fossil fuels boosts atmospheric levels of carbon dioxide and other so-called greenhouse gases, which raises temperatures by trapping heat from the sun that otherwise would flow into space. Coal-burning power plants are the biggest polluters in the U.S., followed by exhaust-spewing cars, trucks and other gasoline-powered vehicles.
"It will continue to warm, not necessarily year by year, but in the long term, until we get emissions under control," Schmidt said.
President Donald Trump's well-known skepticism of climate science notwithstanding, the U.S. populace is starting to catch up with scientists. A new poll shows that 74 percent of Americans now believe global warming is real, with 62 percent saying human activity is the cause.
If the cause of global warming is now well established, so are its effects.
"We can see it in sea level rise and increased coastal flooding, increased heat waves, intense precipitation events, melting ice in the Arctic, mountain glaciers across the world, and ice sheets in Greenland and Antarctica," Schmidt said. "The potential threat of more warming is ever-clearer changes that will reach to wildfires, droughts, storm surge and tropical storm intensity."
Experts say high temperatures are also beginning to exact a number of societal costs, including reduced labor productivity and disruptions of the food supply, along with health problems ranging from a longer, more intense allergy season to an increased incidence of insect-borne diseases.
"Society might collapse in the next few decades due to climate change, but we are learning more and more about what it will look like," Amir Jina, an environmental economist at the University of Chicago, said in an email. As days get hotter, he said, people "use more energy to cool ... work less, and are less effective at work, and food production, especially in the eastern half of the country, can see yield declines of around 50 percent" by the end of the century.
"The majority of people on this planet have never experienced a month when the global average temperature was below the historical average," Dahl said in the email. "And most teenagers have lived almost their entire lives during years of record-breaking temperatures. The continuation of these trends puts the well-being of our planet and all its inhabitants at risk."
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