July 2017: Earth's 1st or 2nd Warmest July on Record

All-time national heat records set or tied in 2017 : 10
All-time national cold records set in 2017 : 2

Dr. Jeff Masters · August 17, 2017, 10:19 PM

July 2017 was the planet's second warmest July since record keeping began in 1880, said NOAA's National Centers for Environmental Information (NCEI) on Thursday. NASA rated July 2017 as the warmest July on record, which means it was also tied for first place as Earth’s warmest month in recorded history (see Joe Romm’s report on this at climateprogress.org.) The only warmer July, according to NOAA, came during the strong El Niño of 2016. Minor differences can occur between the NASA and NOAA rankings because of their different techniques for analyzing data-sparse regions such as the Arctic.

Global ocean temperatures last month were the third warmest on record for any July, according to NOAA, and global land temperatures were the warmest on record. Global satellite-measured temperatures for the lowest 8 km of the atmosphere were the 4th warmest for any July in the 39-year record, according to the University of Alabama Huntsville (UAH) and Remote Sensing Systems (RSS).

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Second-warmest year on record thus far

Each of the first seven months of 2017 have ranked among the top three warmest such months on record, giving 2017 the second highest January–July temperature in the 138-year record: 0.90°C (1.62°F) above the 20th century average of 13.5°C (56.3°F). This is behind the record year of 2016 by 0.14°C (0.25°F). This near-record warmth is especially remarkable given the lack of an El Niño event this year. Global temperatures tend to be warmer during El Niño years, when the ocean releases more heat to the atmosphere. Given the lack of an El Niño event in 2017, it is unlikely that we will surpass 2016 as the warmest year on record.

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Arctic sea ice extent during July 2017 was the fifth lowest in the 38-year satellite record, according to the National Snow and Ice Data Center (NSIDC).

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Sea ice surrounding Antarctica has been at unprecedented lows in recent months, setting an all-time monthly minimum extent record each month during the five-month period November 2016 – March 2017, and again in July of 2017. Monthly Antarctic sea ice extent in April, May and June of 2017 were the second lowest on record for their respective months.

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