NASA scientists say it's no surprise that this past season was the hottest on Earth since records began in 1880. Researchers at the Goddard Institute for Space Studies (GISS) in New York announced that temperatures have hit record highs for several consecutive months.
Temperatures in June, July and August combined were 0.41°F (0.23°C) warmer than the NASA record and 2.1°F (1.2°C) warmer than the average summer temperature from 1951 to 1980. Temperatures in August are 2.2°F (1.2°C) above average.
Not surprisingly, June, July and August all broke records for the hottest months to date. July temperatures were 0.24°C above the 2019 best (0.43°F), and the top five warmest Julys on record have all occurred in the past five years.
"The record temperatures in the summer of 2023 are more than just a set of numbers - they have serious real-world consequences," said NASA Administrator Bill Nelson. "From scorching temperatures in Arizona and across the country, to wildfires across Canada, and devastating floods in Europe and Asia, extreme weather is threatening lives and livelihoods around the world."
NASA's temperature record, GISTEMP, is derived from surface air temperature data provided by tens of thousands of weather stations, as well as sea surface temperature data from ships and buoys. The analysis of the raw data took into account the spacing of temperature stations on the planet and the influence of urban heating.
"Unusually high sea surface temperatures, driven in part by the return of El Niño, are largely responsible for this summer's record warmth," said Josh Willis, a climate scientist and oceanographer at NASA's Jet Propulsion Laboratory in Southern California.
The Southern Hemisphere is currently preparing for the El Niño Southern Oscillation (ENSO), with the World Meteorological Organization (WMO) predicting a 90% chance of a "moderate intensity" El Niño arriving in spring 2023.
Professor Petteri Taalas, Secretary-General of the World Meteorological Organization, said in a statement in July: "The occurrence of El Niño will greatly increase the possibility of breaking temperature records and triggering more extreme heat in many regions and oceans around the world."
Naturally occurring El Niño events typically occur every two to seven years and result from warm currents rising to the surface in the central and eastern tropical Pacific. This has a huge impact on seasonal weather, exacerbating events such as heat waves and flooding.
This may be just a temporary reprieve as the U.S. heads into winter. Data collected over decades by agencies such as NASA and NOAA show that El Niño is exacerbated by human-driven global warming.
"With background warming and marine heat waves that have been creeping in for decades, this El Niño set us off to set all kinds of records," Willis said. "The heat waves we're experiencing now are longer, hotter, and more damaging. The atmosphere can also hold more water now, and it's harder for the body to regulate body temperature in hot and humid environments."
Earlier this year, the United Nations Intergovernmental Panel on Climate Change (IPCC) found that global temperatures could rise by 2.7°F (1.5°C) by the early 2030s. This is earlier than the earlier forecast of 2050.
In addition to more summer records to be broken, this growth raises a number of other serious concerns, including the increasing prevalence of new zoonotic diseases, species extinctions that paralyze international agreements on biodiversity targets, and food and water security issues.
"Unfortunately, climate change is happening," said climate scientist Gavin Schmidt, director of GISS. "What we said would happen is happening. If we continue to pump carbon dioxide and other greenhouse gases into the atmosphere, things will get worse."