Overall, 2018 was the fourth-warmest year on record. Only the three preceding years have been hotter. And these global records will likely be broken soon. Climate change trends suggest Earth’s fever will continue to climb, scientists reported on February 6. They spoke at a joint news conference by the National Oceanic and Atmospheric Administration and NASA.
The agencies collected data on global temperatures throughout 2018. These show that 2018 was 0.79 degree Celsius (1.4 degrees Fahrenheit) warmer than the 20th century average of 13.9 °C (57.0 °F).
A warming trend started around the mid-1970s. It “very much resembles riding up an escalator over time,” said Deke Arndt. He heads NOAA’s global monitoring branch in Asheville, N.C.
In much of the Southern Hemisphere, 2018 scored record average highs for the second year in a row. Some Northern Hemisphere regions also recorded their hottest average temperatures. These included parts of Europe, the Middle East and the Western Pacific. And Arctic temps have continued rising faster than the global average.
Climate change also is leading to more erratic rains across much of the world. A warmer atmosphere holds more water vapor. That can both prolong droughts and also lead to bigger downpours once the water is released. “There’s obviously a connection there,” Arndt said.
The United States experienced its wettest year since 1983. Record rains flooded nine eastern states. These include Pennsylvania, Virginia and Maryland. Nationwide, average annual rainfall totaled 87.96 centimeters (34.63 inches). That’s 11.9 cm (4.69 in) above the 20th century average.
"The key message is that the planet is warming," said Gavin Schmidt. He directs NASA’s Goddard Institute for Space Studies in New York City. That trend shows up, he says, no matter how the data are sliced.
“The long-term trends are extremely robust,” Schmidt added. “Our understanding of why those trends are occurring is also very robust. It’s because of increases in greenhouse gases.”
annual Adjective for something that happens every year. (in botany) A plant that lives only one year, so it usually has a showy flower and produces many seeds.
Arctic A region that falls within the Arctic Circle. The edge of that circle is defined as the northernmost point at which the sun is visible on the northern winter solstice and the southernmost point at which the midnight sun can be seen on the northern summer solstice. The high Arctic is that most northerly third of this region. It’s a region dominated by snow cover much of the year.
atmosphere The envelope of gases surrounding Earth or another planet.
average (in science) A term for the arithmetic mean, which is the sum of a group of numbers that is then divided by the size of the group.
climate The weather conditions that typically exist in one area, in general, or over a long period.
climate change Long-term, significant change in the climate of Earth. It can happen naturally or in response to human activities, including the burning of fossil fuels and clearing of forests.
drought An extended period of abnormally low rainfall; a shortage of water resulting from this.
erratic A pattern that appears irregular and unpredictable.
greenhouse A light-filled structure, often with windows serving as walls and ceiling materials, in which plants are grown. It provides a controlled environment in which set amounts of water, humidity and nutrients can be applied — and pests can be prevented entry.
NASA Short for the National Aeronautics and Space Administration. Created in 1958, this U.S. agency has become a leader in space research and in stimulating public interest in space exploration. It was through NASA that the United States sent people into orbit and ultimately to the moon. It also has sent research craft to study planets and other celestial objects in our solar system.
National Oceanic and Atmospheric Administration (or NOAA) A science agency of the U.S. Department of Commerce. Initially established in 1807 under another name (The Survey of the Coast), this agency focuses on understanding and preserving ocean resources, including fisheries, protecting marine mammals (from seals to whales), studying the seafloor and probing the upper atmosphere.
Pacific The largest of the world’s five oceans. It separates Asia and Australia to the west from North and South America to the east.
water vapor Water in its gaseous state, capable of being suspended in the air.
Report: NASA, NOAA. Annual global analysis for 2018. February 2019.
Press release: NASA. 2018 fourth warmest year in continued warming trend, according to NASA, NOAA. Published online February 6, 2019.