Hospital staff pour water for a patient who is suffering from heatstroke in a government hospital in Varanasi, India, during a heat wave on May 30, 2024. INDRANIL ADITYA/NURPHOTO VIA GETTY IMAGES

The world has now marked one full year of back-to-back monthly heat records, the European Union's Copernicus Climate Change Service announced on Wednesday. It said last month was the hottest May in recorded history — the 12th consecutive month in which the monthly high temperature record was broken.

It was also the 11th consecutive month where the global average temperature was at least 1.5 degrees Celsius above the pre-industrial average. If that trend continues, it would mean the world is passing a major climate change milestone.

May's average temperature was 1.52 degrees Celsius above the pre-industrial average, Copernicus reported, while the global average temperature from June 2023 to May 2024 was 1.63 degrees Celsius above the pre-industrial average.

The pre-industrial average refers to the period before there was a sharp increase in emissions of greenhouse gases, which trap heat from the sun within the Earth's atmosphere and warm the planet. Experts have long warned that keeping average global temperatures no more than 1.5 degrees Celsius above that mark is critical to reduce the risk of rampant damage caused by rising global temperatures. As the planet warms, the heat leads to more precipitation and melting sea ice, fueling extreme weather conditions that can result in shifting coastlines, agricultural issues, mass migration and harmful health consequences.

Carlo Buontempo, director of the Copernicus Climate Change Service, said that the 12-month streak "is shocking but not surprising," and that while the streak will likely see an interruption at some point, "the overall signature of climate change remains."

"There is no sign in sight of a change in such a trend," he said. "We are living in unprecedented times. ... This string of hottest months will be remembered as comparatively cold."

While surpassing 1.5 degrees of warming every month for nearly a year indicates a worrying trend, scientists say, it will take several years of continued high temperatures for the world to officially pass that benchmark. However, deadly heat waves, floods, hurricanes and other conditions have already been worsening as the climate changes.

"Millions of people globally are already experiencing impacts of climate change," NOAA's climate.gov says. "...The 1.5°C climate threshold is not a light switch that turns on all sorts of climate calamities. For every little bit of additional warming, the risk of negative impacts gets worse."

The primary way to reduce the rise in global temperatures is to minimize greenhouse gas emissions. Doing so requires reducing the burning of fossil fuels, such as oil and coal, as they release the bulk of these gases. Climate experts at the United Nations explain that carbon dioxide is the most abundant of these gases, while methane is the most potent, making up more than a quarter of all global warming.

Buontempo said that if the world acts quickly to reduce concentrations of these gases, "we might be able to return to these 'cold' temperatures by the end of the century."

For now, the heat is only expected to continue. In the U.S., officials are forecasting another summer of dangerously high temperatures across most of the country. California is already facing wildfires and the Southeast is bracing for an intense hurricane season. In the past week, dozens of people in India have died because of scorching heat, while last month, deadly floods struck Afghanistan and Brazil.

"It's climate crunch time," U.N. Secretary-General António Guterres said in a statement. "...Our planet is trying to tell us something. But we don't seem to be listening. We're shattering global temperature records and reaping the whirlwind."


Monthly global surface air temperature anomalies (°C) relative to 1850–1900, from January 1940 to May 2024, plotted as time series for each year spanning June to May of the following year. C3S/ECMWF