With hot October temperatures, this is 'virtually certain' to be the warmest year on record

Wispy clouds float across the sky as beachgoers exercise at Santa Monica Beach on a recent afternoon. .
People exercise at Santa Monica Beach last month, the hottest October on record. (Luis Sinco / Los Angeles Times)

Following another month of record-shattering temperatures, European scientists said Wednesday that 2023 is “virtually certain” to go down as the planet’s hottest year on record.

Last month was the hottest October ever recorded, with an average global surface temperature of 59.5 degrees Fahrenheit— about 3.1 degrees warmer than the preindustrial average, according to Copernicus Climate Change Service, the European climate agency. It was 0.7 of a degree warmer than the previous warmest October in 2019.

It was the fifth consecutive month that Earth set such a record, with officials indicating that the planet is growing perilously close to 1.5 degrees Celsius (2.7 degrees Fahrenheit) of global warming, an internationally recognized tipping point for the worst effects of climate change. The number stems from the 2015 Paris climate agreement, which found that if temperatures increase an average of 1.5 degrees over preindustrial numbers, the planet will cross a threshold that “risks unleashing far more severe climate change impacts,” including more frequent and severe droughts, heat waves and rainfall.

“October 2023 has seen exceptional temperature anomalies, following on from four months of global temperature records being obliterated,” said Samantha Burgess, Copernicus’ deputy director. “We can say with near certainty that 2023 will be the warmest year on record, and is currently 1.43 degrees Celsius above the preindustrial average.”

The month was also marked by record warm sea surface temperatures and record low sea ice extent, or the amount of ice covering the ocean at a given time, Copernicus found. Antarctic sea ice was 11% below its monthly average, a record low amount, while Arctic sea ice was 12% below its monthly average, its seventh lowest on record.

The average sea surface temperature in non-polar regions was about 69 degrees, also the highest on record for October.

The United States has fared slightly better than the globe, with October ranking as the 18th warmest on record in the contiguous U.S., at an average temperature of 56.1 degrees, according to a separate report from the National Oceanic and Atmospheric Administration.

However, 317 U.S. counties have recorded their warmest January through October on record this year, the agency said.

Read more: A warm, wet El Niño winter is in store for California and much of the U.S.

The last five months have stunned scientists, with some warning that Earth is warming faster than expected. In a post on X, formerly known as Twitter, climate scientist Zeke Hausfather called the September data “absolutely gobsmackingly bananas.”

There are several factors that may be contributing to the rapid warming, including a strengthening El Niño system. El Niño, a climate pattern in the tropical Pacific, is a major driver of weather patterns worldwide, and is associated with warmer global temperatures.

But the strongest and clearest driver of planetary warming is the burning of fossil fuels.

“The only reason within a reasonable degree of certainty that the Earth is warming — because all the other factors right now are so small by comparison — is the emission of greenhouse gases into the atmosphere,” UCLA climate scientist Daniel Swain said in a briefing this week.

It is against that backdrop, however, that researchers have been quibbling about other potential causes of rapid planetary warming. A study published this month by renowned climate scientist James Hansen found that the pace of warming is accelerating, and that Earth’s climate is more sensitive than previously estimated.

Among other findings, Hansen said a recent change in aerosol shipping regulations may be a contributing factor. The regulations reduced the upper limit of sulfur allowed in fuels in an effort to clean up air pollution in ports and coastal areas, but may have had an unintended planetary warming effect because the aerosols were reflecting sunlight away from Earth.

However, other scientists disagreed, with University of Pennsylvania professor Michael Mann arguing in a post on his website that warming is increasing steadily, rather than accelerating, and that aerosols play a minimal role.

What both agreed on, though, is that urgent action is required to curb human-caused climate change.

“There is no reason that we can’t prevent dangerous levels of warming through concerted efforts to decarbonize the global economy,” Mann wrote.

Read more: U.N. report warns of catastrophic climate tipping points. California is nearing several

Weighing in on the debate, Swain said there is “no doubting” that Earth’s temperature surge this year has been extraordinary and record-breaking, but that it was within the range of possibilities.

“As shocking as this year has been — and as dramatic as the global extremes and temperature and precipitation we’ve witnessed have actually been — we’re not really outside of the central zone of predictions of what 2023 might have looked like on a global average basis,” he said. “Now in terms of individual extreme heat waves and individual extreme precipitation events, that may be quite a different story.”

Indeed, the year has been marked by a record-breaking number of billion-dollar climate disasters, according to NOAA. That includes record-shattering heat waves in parts of China, Europe and the American Southwest; devastating hurricanes in Florida and Mexico; ongoing wildfires in Canada and catastrophic flooding in California earlier this year.

In October, the Mississippi River shrank to record lows due to warm temperatures and ongoing drought in the region, the agency said.

Forecasters say California could be facing another wet winter driven by El Niño, including more levee breaches and flooding across the state.

Burgess, of Copernicus, noted that October’s eye-popping temperature report arrives just weeks ahead of COP28, an international climate conference that will be held this year in Dubai.

“The sense of urgency for ambitious climate action going into COP28 has never been higher,” she said.

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This story originally appeared in Los Angeles Times.