The average global land and ocean surface temperature for June, July, and August—the Northern Hemisphere’s meteorological summer—was higher for that period than it has been since global records began in 1850, the U.S. National Oceanic and Atmospheric Administration (NOAA) announced in September.
United Nations Secretary-General António Guterres reacted to the news with a dire warning. “Climate breakdown has begun,” he said in a statement.
“Scientists have long warned what our fossil fuel addiction will unleash,” he added. “Our climate is imploding faster than we can cope, with extreme weather events hitting every corner of the planet.”
The impacts have certainly been evident across the Americas, in the form of fast-moving tropical storms, deadly localized heat waves, coral bleaching, and out-of-control wildfires, to name just a few.
Canada has had a devastating wildfire season; as of September 15, more than 17 million hectares had burned so far this year, a more than 85% increase over the 25-year average for that period, according to the Canadian Interagency Forest Fire Centre.
In the Southwestern United States, the city of Phoenix, Arizona, saw temperatures climb to at least 110 degrees Fahrenheit (43.3° Celsius) for 31 days in a row this summer, breaking a previous record of 18 straight days set in 1974.
At least Arizona was supposed to be hot at that time of year. Several South American countries, by contrast, experienced “mini-summers” during their winter. On August 24, temperatures reached 38.7°C (101.7°F) in Rio de Janeiro, Brazil; the day before, Villamontes, Bolivia, had seen a high of 45°C (113°F), reportedly tying the hottest winter temperature on record in the Southern Hemisphere.
In a recent analysis, a nonprofit independent group called Climate Central estimated that more than 3.8 billion people—nearly half the world’s population—experienced extreme, climate-driven heat for at least 30 days in June, July, and August. For 1.5 billion people, extreme heat was a daily experience during that period.
The organization’s Climate Shift Index (CSI) maps the influence of climate change on daily temperatures across the globe. A CSI of level of 3, for example, indicates that human-caused climate change made the extreme temperatures at least three times more likely.
In its analysis, Climate Central listed areas around the world where “very strong fingerprints of climate change (CSI level 3 or higher) persisted for at least half of the June-August 2023 period.” Among the areas in the Americas: the Amazon Basin, the Andes, Central America and the Caribbean, Mexico, the southern tier of the United States, and western Canada.
If all this seems a little overwhelming, you are not alone. The New York Times recently reported on the increasing levels of “eco-anxiety” that mental health professionals are seeing, quoting experts who defined the term as a “chronic fear of environmental doom.”
What on earth is happening? What accounts for all this record-breaking heat? Two NOAA experts talked to the Energy and Climate Partnership of the Americas (ECPA) about some of the factors at play and the risks ahead—and even some glimmers of hope from the world’s youth.
First, it’s important to remember that not every change in the weather is about climate change. “Mother Nature can do weird things sometimes,” said Tom DiLiberto, a climate scientist and public affairs specialist at NOAA. What climate change does, he said, is set the stage for more-intense weather events.
“It’s making it easier for extremes to happen,” he said. The overall warming of the planet has the effect of “loading the dice,” as he put it. Or, he added, it’s like giving a basketball player a height advantage by putting a stepladder under the basket.
“Climate change is basically giving you a stepladder for those sorts of high extremes, to reach higher heights,” DiLiberto said. In the past 50 to 70 years, he said, “we’ve seen heat waves last longer, we’ve seen them be stronger, we’ve seen them occur more frequently.”
One factor this year that especially worries climate scientists is the average surface temperature of the ocean. “The oceans pretty much everywhere are warm,” DiLiberto said.
That ocean warming is partly related to climate change, he added, and partly to this year’s El Niño, the warming pattern seen periodically in the tropical Pacific Ocean. El Niño “jumbles up” the atmosphere around the equator and causes changes in precipitation patterns, he explained.
Science still lacks a sure answer about the effects of climate change on El Niño, “but what we can say with confidence is that climate change is going to impact the impacts from El Niño,” DiLiberto said. In other words, areas that would be drier than average in an El Niño year will be even drier due to climate change, while rainy areas will be even wetter.
Normally, DiLiberto said, El Niño tends to be associated with below-average Atlantic hurricane seasons, but this year’s record-breaking ocean temperatures have contributed to some rapidly intensifying tropical storms—such as Hurricane Idalia, which swept through the Southeastern U.S. at the end of August.
“It’s scary to see the oceans this warm in a hurricane season because you know there’s just so much fuel available for hurricanes,” DiLiberto said.
Just how hot was the planet in June, July, and August?
Some places around the globe have seen unusually heavy precipitation this year and, in some cases, drought and wildfires have alternated with flooding rains. “These flips between dry and wet are really difficult to plan for, and they’re really difficult to build back from constantly,” DiLiberto said.
Another cause for concern this year, he said, has been the extreme temperatures in places with relatively high humidity. “It does not give the human body the ability to cool itself off the way it normally does,” he said, increasing the risk of heat stroke or other heat-related illnesses.
The effects of heat on the body are especially intense in urban areas, according to Rafael de Ameller, who works for a NOAA contractor as lead of the NOAA Environmental Visualization Lab (known as VizLab).
“It’s like we’re building cities purposely to absorb heat,” de Ameller said. That, he added, is a health issue: “It’s like a heat pandemic.”
Within metropolitan areas, there are “heat islands” where average temperatures may be considerably higher than in the city as a whole, due to the amount of asphalt and the lack of green spaces and mature trees. In the United States, at least, those urban heat islands often match up with socioeconomically disadvantaged areas, de Ameller said.
“There’s not only heat baked into these systems, but there’s also this inequity baked into how our cities are built,” he added.
Heat-related deaths tend to be underreported by hospitals, he said, because the effect of heat is not always obvious. Someone who was working outside in the sun and collapsed from hyperthermia would probably be recorded as an official heat-related death; however, someone who died of a heart attack or a stroke after days of excess heat would not necessarily appear in those statistics.
Studies try to account for the statistical gaps by tracking “excess mortality” rates from heat. In July, one study estimated that heat waves in the summer of 2022 killed more than 61,000 people in Europe.
In the United States, an interagency effort led by NOAA—called the National Integrated Heat Health Information System—is mapping heat islands in cities to better understand where to take action first, de Ameller said. For example, a decision about where to deploy a cooling center should take into account not just the temperature but local residents’ economic situation. An area where people can’t afford air conditioning would be a higher priority than an affluent neighborhood.
DiLiberto said that when he talks to groups around the U.S., he is always amazed at how much people are doing at the local level to make their cities more climate-resilient and decrease emissions from greenhouse gases. This can sometimes feel like a lonely effort, he said. In fact, he will often ask his audience who feels alone, “and they all raise their hand.”
On a global scale, he said, climate conferences no longer focus on just the science of climate change but now look at such issues as how to finance climate-related measures and how to ensure that the voices of the most vulnerable communities are heard.
DiLiberto has attended several Conferences of the Parties to the United Nations Framework Convention on Climate Change (the annual so-called COP events), including COP21 in Paris, where the Paris Agreement on climate was adopted, and he plans to be in Dubai for COP28, which begins on November 30.
He said he has been heartened in recent years by the growing passion and energy on the subject of climate change, especially from the youth movement. “The shift in those events is just incredible,” he said. “It’s all about actions. It’s all about solutions.”
Just how hot was the planet in June, July, and August? The numbers vary slightly, depending on what agency is doing the measuring and what historical period is being used as a comparison, but here are some sample readings:
In May, a WMO report said global temperatures are likely to surge to record levels in the next five years. It said there is a 66% likelihood that average global temperatures between 2023 and 2027 will exceed 1.5°C above preindustrial levels for at least one year, and put the likelihood that one of those years will be the warmest on record at 98%.
That does not mean the planet will permanently exceed the long-term threshold specified in the Paris Agreement, the WMO Secretary-General, Prof. Petteri Taalas, said in a news release. “However,” he said, “WMO is sounding the alarm that we will breach the 1.5°C level on a temporary basis with increasing frequency.”