According to the National Aeronautics and Space Administration (NASA), 2017 was the second warmest year in surface temperatures averaged across the entire Earth since global estimates began in 1880. So what should we expect for 2018?
The only warmer year than 2017 on record was 2016, when temperatures were bolstered by an El Niño, which typically causes warming effects around the globe due to the warmer water in the tropical Pacific Ocean. Thus, 2017 was the warmest year without an El Niño event (see Fig. 1).
Fig. 1: Years in which an El Niño effect occurred have been warmer, on average, than those without. Credit: NASA
Earth’s average temperatures in 2017 were 1.62 degrees Fahrenheit warmer than the 1951–to–1980 mean, according to NASA scientists. The year continued a decades-long warming trend around the globe, in which 17 of the 18 warmest years have now occurred since 2001. The only one of the 18 warmest years that occurred in the 20th century was during the El Niño event of 1998.
Scientists from the National Oceanic and Atmospheric Administration (NOAA) produced a separate, independent analysis that concluded that 2017 was the third warmest year of record across Earth. Minor differences between the NOAA and NASA estimates are due to different methods used for analyzing the temperature data. Both reports found that the five warmest years on record have all taken place since 2010.
The NOAA report also found that 2017 was the third warmest year on record for the 48 contiguous United States, with an average annual temperature that was 2.6 degrees Fahrenheit above the 20th-century average. This was slightly cooler than 2012 and 2016, but it marks the 21st consecutive warmer-than-average year for the country.
Every one of the contiguous 48 states had above-normal temperatures in 2017 (see Fig. 2). For five states—Arizona, Georgia, New Mexico, North Carolina, and South Carolina—2017 was the warmest year on record. In 32 additional states, including Alaska, 2017 ranked among the 10 warmest years since 1895. This is the third consecutive year in which every state across the lower 48 states has had an above-average annual temperature.
Fig. 2: Mean temperatures of 2017 across the contiguous United States. Credit: NOAA
Although 2018 got off to a cold start in many places, we expect that 2018 overall will continue the warm trend, with above-normal temperatures expected, on average, during the coming year across both the United States and Canada.
Read more about the El Niño and La Niña effects.
See last month’s Weather Update blog!