NASA Confirms That 2023 was the Hottest Summer on Record

Yesterday, NASA’s Goddard Institute of Space Studies (GISS) announced that the summer of 2003 was the hottest on record. This year saw a massive heat wave that swept across much of the world and was felt in South America, Japan, Europe, and the U.S. This exacerbated deadly wildfires in Canada and Hawaii (predominantly on the island of Maui) and are likely to have contributed to severe rainfall in Italy, Greece, and Central Europe. This is the latest in a string of record-setting summers that are the direct result of anthropogenic climate change.

According to GISTEMP, the months of June, July, and August combined were 0.23 °C (0.41 °F) warmer than any other summer on record and 1.2 °C (2.1 °F) warmer than the seasonal average between 1951 and 1980. Said NASA Administrator Bill Nelson in a NASA press release:

“Summer 2023’s record-setting temperatures aren’t just a set of numbers – they result in dire real-world consequences. From sweltering temperatures in Arizona and across the country, to wildfires across Canada, and extreme flooding in Europe and Asia, extreme weather is threatening lives and livelihoods around the world. The impacts of climate change are a threat to our planet and future generations, threats that NASA and the Biden-Harris Administration are tackling head on.”

This chart shows the meteorological summer (June, July, and August) temperature anomalies each year since 1880. Credit: NASA’s Earth Observatory/Lauren Dauphin

NASA’s temperature record, known as GISTEMP, is assembled based on surface air temperature data acquired by tens of thousands of meteorological stations worldwide. This combines sea surface temperature data from ship- and buoy-based instruments. The raw data is then analyzed using methods that account for local temperature differences and urban heating effects that could otherwise throw off the calculations. Rather than calculating absolute surface air temperature (SAT), the analysis calculates temperature anomalies – i.e., how far the temperature has departed from the 1951-1980 base average.

This coincided with exceptionally high sea surface temperatures (SST), according to data released in August by the National Oceanic and Atmospheric Administration (NOAA). This trend became apparent in March and April when scientists began to notice that average temperatures had surpassed the highest levels recorded by the NOAA. By July, global sea surface temperatures reached 0.99°C (1.78°F) above the average, the fourth consecutive month they were at record levels. According to Josh Willis, a climate scientist and oceanographer at NASA’s Jet Propulsion Laboratory, this trend was fueled in part by the return of El Niño and was largely responsible for the summer’s record warmth:

“There are a lot of things that affect the world’s sea surface temperatures, but two main factors have pushed them to record heights. We have an El Niño developing in the Pacific, and that’s on top of long-term global warming that has been pushing ocean temperatures steadily upward almost everywhere for a century.”

Further: NASA

Matt Williams

Matt Williams is a space journalist and science communicator for Universe Today and Interesting Engineering. He's also a science fiction author, podcaster (Stories from Space), and Taekwon-Do instructor who lives on Vancouver Island with his wife and family.

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