Summer of 2023 will be hottest since 2000, study finds

Extreme summers marked by deadly heat waves, explosive wildfires and record-warming ocean temperatures will decline, becoming one of the hottest in the past 2,000 years, new research finds.

According to a study published Tuesday in the journal Nature, temperatures in the Northern Hemisphere during the summer of 2023 were 3.72 degrees warmer than the average between 1850 and 1900, the beginning of modern instrumental record keeping. The study focused on surface air temperatures in the temperate zone, a region between 30 and 90 degrees north latitude that includes much of Europe and North America.

Temperatures in June, July and August last year were also 3.96 degrees warmer than the average from 1 to 1890, which the researchers calculated by combining observational records with tree-ring records from nine regions around the world. .

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Jan Esper, the study’s lead author and a professor of climate geography at Johannes Gutenberg University in Germany, said he did not expect last summer to be so unusual, but he was ultimately not surprised by the findings. The high temperatures build on an overall warming trend driven by greenhouse gas emissions and are further exacerbated by the onset of El Niño in the tropical Pacific.

“It’s not surprising — it’s been a really, really good 2023 — but it’s also a continuation of a trend that’s going to continue,” Esper told reporters on Monday. “Personally, I don’t Surprised, but worried.”

He said extreme temperatures in 2023 are important to consider in the long term. The study found that the region’s previous hottest summer (year 246) differed by 2.14 degrees from the summer of 2023.

The heat here is even worse than during the region’s coldest summers—much of it driven by volcanic eruptions that spew heat-blocking sulfur into the stratosphere. According to the study, the summer of 2023 was 7.07 degrees warmer than the coldest summer in the reconstructed period (536 years).

“Although 2023 is consistent with greenhouse gas-induced warming, which is exacerbated by El Niño, this extreme scenario underscores the urgency of implementing international carbon reduction agreements,” the study said.

The scorching summer temperatures have led to dozens of heat illnesses and deaths, including at least 645 heat-related deaths in Maricopa County, Arizona, and a record 31 consecutive days of temperatures reaching 110 degrees or higher in Phoenix.

High temperatures are fueling wildfires raging across Canada and sending harmful smoke up the U.S. East Coast and across the Atlantic. Meanwhile, ocean temperatures off the Florida coast soared to more than 101 degrees, the equivalent of a hot tub.

Several climate agencies, including the U.S. National Oceanic and Atmospheric Administration and the European Union’s Copernicus Climate Change Service, have declared 2023 to be the hottest year on record.

Notably, Copernicus found that last summer’s summer months of June, July and August were 1.18 degrees warmer than average – still hot, but nowhere near as warm as findings from the northern hemisphere tropics.

Karen McKinnon, an assistant professor of statistics and environment at UCLA who was not involved in the study, said the region is particularly hot in part because it has so much land that is warming faster than the ocean Even faster. (June, July, and August are also winter months in the Southern Hemisphere.)

MacKinnon said the study’s results were not surprising because it was already well documented that summer temperatures in 2023 were record-breaking compared to measurable data from the mid-1800s. But by going back 2,000 years, the researchers also helped illuminate “all kinds of natural changes that may have occurred in the past,” she said.

She points out that tree rings can be useful indicators of past climate conditions because trees tend to grow faster in a given year if they receive the right amount of warmth, water and sunlight.

While last year’s hot weather is undeniable, the study also highlights that summer temperatures in the region were significantly higher than the global target of 2.7 degrees Celsius (or 1.5 degrees Celsius) of warming from pre-industrial times, set by the Intergovernmental Panel on Climate Change .

It also notes that some recent studies have found that the data used to calculate the baseline can be off by a few tenths of a degree, meaning recalibration may be needed to target landings closer to the more challenging 1.6 or 1.7 degrees.

“I don’t think we should use proxy data in place of instrumental data, but there is a good indication that there is a warmth bias,” Esper said. “Further research is needed.”

McKinnon said there was always a degree of uncertainty when comparing current temperatures to past temperatures, but the 1.5-degree limit was both symbolic and practical. Many of the effects of climate change, including worsening heat waves, are already beginning to be felt.

“There are definitely tipping points in the climate system, but we don’t understand the climate system well enough to say that 1.5°C is this There are certain tipping temperatures,” she said. “It’s just a policy goal that it would bring about temperature changes that might be consistent with avoiding some damage.”

Indeed, just days before the study was published, an IPCC survey of 380 leading scientists revealed deep concerns about the world’s ability to limit global warming to 1.5 degrees. The report, published in The Guardian last week, found that only 6% of scientists surveyed believed the 1.5-degree limit could be reached. Nearly 80% said they expected temperatures to rise by at least 2.5 degrees Celsius.

The report caused a stir in the scientific community, with some saying it focused too much on pessimism and despair. But Daniel Swain, a climate scientist at the University of California, Los Angeles who participated in the survey, said its findings are worth considering.

“Many scientists, myself included, are very worried and concerned and increasingly alarmed by what is happening and what the data shows,” Swain said at a news conference on Friday. “But if anything, I think it does create a stronger sense of determination and urgency to do more and do better.”

Indeed, while scientists are still weighing whether or how quickly humans can change the Earth’s worsening warming trajectory, Esper said he hopes the latest research can be an impetus to change outdated energy consumption patterns that have led to Greenhouse gas emissions that warm the planet.

“I’m worried about global warming – I think it’s one of the biggest threats,” he said.

He added that he was particularly worried about his children and younger generations, who will bear the brunt of worsening heat and other adverse climate consequences. The summer of 2024 is likely to be hotter, the study said.

“The longer we wait, the broader the impact will be, and the harder it will be to mitigate or even stop this process and turn things around,” Esper said. “It’s clear: We should be doing as much as possible as quickly as possible.”