In a surprising finding, NASA released data Tuesday showing that July 2017 is tied for the warmest such month on record, statistically deadlocked with July 2016. This means that July was one of the warmest months the planet has seen in 137 years of record-keeping, comparable to July and August 2016, which tied for the record for the warmest month overall.
What makes this year's July record noteworthy is that it occurred in the absence of a natural climate cycle, like El Niño, which would help heighten global average surface temperatures. A strong El Niño, combined with human-caused global warming, helped push 2016 to claim the record for the warmest year since reliable thermometer records began in 1880.
In addition, the finding comes during a summer in which large parts of the Arctic have seen below average temperatures, bucking the recent sharp warming trend there. (Critics of NASA's temperature data sometimes argue that Arctic warming skews the agency's figures so they are biased as too high.)
The global average temperature during July 2017 was 0.83 degrees Celsius, or 1.49 degrees Fahrenheit, above the monthly average, NASA found. (NASA uses a 1951 to 1980 baseline for its temperature reports.)
"Only July 2016 showed a similarly high temperature [0.82 degrees Celsius above average], all previous months of July were more than a tenth of a degree cooler," NASA stated in a press release.
NASA’s temperature figures for July 2017 are preliminary, and may change as more data is examined and methods are refined, according to Gavin Schmidt, the director of NASA’s Goddard Institute for Space Studies in New York.
July 2017 compared to the same period during the other hottest years.
Image: nasa giss
July is typically the planet's hottest month of the year, and increasingly features extreme heat waves, wildfires, and deluges, all of which have been linked in some way to global warming. This year was no exception, with wildfires consuming well over a million acres in British Columbia, and breaking out amid searing heat waves in Spain, Italy, and other parts of southern Europe.
A severe and prolonged European heat wave was bad enough to be nicknamed "Lucifer." Spain, France, Serbia, Romania, and Croatia were especially hard hit.
Climate scientists have yet to study many of the specific extreme events underway around the world, but the July heat prompted an investigation from an international team specializing in a form of climate detective work known as extreme event attribution.
The researchers from England, France, Switzerland, and the U.S., found that climate change made the intensity and frequency of the extreme heat at least twice as likely to occur in Belgium, at least four times as likely in France, Switzerland, the Netherlands, and central England, and at least 10 times as likely as Portugal and Spain.
The unusual heat was not limited to Europe, either.
On July 21, Shanghai, China, which is the most populated city in the world with 24 million residents, set a record for its hottest day since record-keeping began there in 1872. The high temperature on that day was 105.6 degrees Fahrenheit, or 40.9 degrees Celsius, and it fits with a pattern of hotter weather in that city.
In addition, during July, Death Valley set the record for not only its hottest month, but the hottest month on record for any location worldwide. The average temperature for the month of July was 107.4 degrees Fahrenheit.
The NASA news release indicates that July 2017 is the first month during which the agency's scientists implemented a new dataset of ocean temperatures. The new data is meant to improve the accuracy of ocean temperature observations, particularly after the 1940s, but it helped boost July's average temperature slightly.
NOAA will release its own global temperature data for the month, which might differ slightly with NASA in terms of the ranking. Overall, 2017 has been tracking as the second-warmest year on record.
The planet has not had a cooler than average month since December of 1984. A forthcoming climate report from 13 different federal agencies is expected to say that human emissions of greenhouse gases likely caused 1.1 to 1.3 degrees Fahrenheit of global warming between the years of 1950 to 2010. This closely matches the observed warming during the period.