According to scientists at NASA’s Goddard Institute for Space Studies (GISS) in New York, July 2023 was hotter than any other month in the global temperature record since data collection began in 1880.
Overall, July 2023 was 0.43°F (0.24°C) warmer than any other July in NASA’s record, and 2.1°F (1.18 °C) warmer than the average July between 1951 and 1980. The primary focus of the GISS analysis is long-term temperature changes over many decades and centuries, and a fixed base period yields anomalies that are consistent over time. Temperature ‘normals’ are defined by several decades or more – typically 30 years.
“NASA data confirms what billions around the world literally felt: temperatures in July 2023 made it the hottest month on record,” said NASA Administrator Bill Nelson. “The science is clear. We must act now to protect our communities and planet. It’s the only one we have.”
Parts of South America, North Africa, North America and the Antarctic Peninsula were particularly hot, experiencing temperatures around 7.2°F (4°C) above average. Overall, extreme heat this summer put tens of millions of people under heat warnings and was linked to hundreds of heat-related illnesses and deaths. The record-breaking July continues a long-term trend of human-driven warming caused primarily by greenhouse gas emissions that has become evident over the past four decades. According to NASA data, the five hottest Julys since 1880 have all happened in the past five years.
NASA assembles its temperature record from surface air temperature data from tens of thousands of metrological stations, as well as sea surface temperature data acquired by ship- and buoy-based instruments. This raw data is analyzed using methods that account for the varied spacing of temperature stations around the globe and for urban heating effects that could skew the calculations.
High sea-surface temperatures contributed to July’s record warmth. NASA’s analysis shows particularly warm ocean temperatures in the eastern tropical Pacific, evidence of the El Niño that began developing in May 2023. Phenomena such as El Niño and La Niña, which warm and cool the tropical Pacific Ocean, can contribute a small amount of year-to-year variability in global temperatures. But these contributions are not typically felt when El Niño starts developing in the northern hemisphere summer. NASA expects to see the biggest impacts of El Niño in February, March and April 2024.
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