Opinion | This Summer Is Pointing Us Toward Uncharted Territory

On the last day of July, Phoenix finally registered a temperature high below 110 degrees Fahrenheit — the first time that had happened in 31 days. The temperature of pavement in the city measured up to 180 degrees, and local burn units are full of patients who simply fell to the ground and were burned, as though Maricopa County’s whole surface were a skillet on the stove. The I.C.U.s are filling up, too, and the region’s iconic saguaro cactuses are crumpling and collapsing in the heat. On the same day last week that President Biden offered only a few meek remarks about extreme heat and just a few million dollars in new funding for heat forecasting, the U.N. secretary general, António Guterres, leaned into a typically vehement formulation. “The era of global warming has ended,” he said. “The era of global boiling has arrived.”

It was, worldwide, the hottest month on record. June was the hottest June on record. August appears poised to be the hottest August. Every single day for four straight weeks, as Canada burned and Sicily burned and Algeria burned, global temperatures surpassed the daily record set in 2016 and matched last summer, when 61,000 Europeans are estimated to have died as a result of the heat.

But what else do you expect as greenhouse gas emissions continue? On opposite ends of the planet, temperatures recorded in the North Atlantic and sea ice measured near the South Pole, tracked so far from recent trends that you might embarrass yourself simply stating the size of the anomaly — a four sigma event in the temperatures of the North Atlantic, meaning that, given a stable climate and a normal distribution of chance, it should be expected about once every few hundred years and perhaps a six sigma event for Antarctic sea ice, meaning we should expect to see it, at least according to the simplified math, only once every 7.5 million years.

At a certain point, that math just gets silly, telling you perhaps more about the improper way you might have structured the comparison than about the size of the anomaly itself. But you can measure the anomalies in other ways, such as by noting the hot-tub ocean temperatures off the Florida Keys, a year’s worth of rain falling in 36 hours in parts of Beijing or 100-degree temperatures in the mountains of Chile or that there is an Argentina-size gap between this year’s Antarctic sea ice and the typical extent. And the fact that we are seeing these gob-smacking anomalies at all is a sign that the historical framework implied by terms like “seven sigma” and “500-year storm,” imperfect in the best of times, no longer applies to the world we live in now.

The environmental journalist Juliet Eilperin called the ocean temperatures “beyond belief”; The Washington Post reported that they had “baffled scientists.” Contemplating the trajectory of Arctic sea ice, the atmospheric scientist Zack Labe wrote memorably about how often he finds himself answering questions about the state of the science these days by saying, “I don’t know.” And for all the uncertainty, many of those watching the changes unfold have a queasy intuition that we may be entering a new climatic regime — and perhaps inching closer to some quite concerning tipping points.

“Shocking but not really surprising,” is how NASA’s Gavin Schmidt put it. “Even the things that are unprecedented are not surprising.” That is where we are all living now, in a climate that is both shocking and unsurprising. For several decades, those anxious about global warming have lived in fear of climate prophecies. We are beginning to simply live within them, a process that looks from some vantages like a horror story and from others surprisingly normal.

There are different ways to measure the changes, some less hair-raising than others. In a report published July 25, the World Weather Attribution network examined recent heat waves in the United States, Europe and China, finding that all but the Chinese event would have been impossible without climate change. In a stable, prewarming climate, the heat wave that baked China would have happened once every 250 years; now, the network said, it should be expected every five years. The episodes in Europe and North America, once impossible, should be expected once every 10 to 15 years. I’d bet on these frequencies being underestimates. Last summer there were 100 million Americans under heat advisories, and heat across Europe was called record-breaking then, as well. (On British television, a broadcaster complained that her meteorologist guest was being too gloomy about the heat; “I want us to be happy about the weather,” she said. In the weeks that followed, several thousand Britons died in the heat.)

But the World Weather Attribution report also characterized the heat waves in another way, incorporating a critique made by Patrick Brown of the Breakthrough Institute last summer to measure the simple size of the temperature anomaly attributable to climate change, too. By this metric, the network found, warming had added just one degree Celsius to the temperatures in China, two degrees to the heat waves in North America and two and a half degrees to southern Europe’s.

The coolheaded climate scientist Zeke Hausfather tried to quickly contextualize the recent string of anomalies to show that, in fact, they were, while alarming, nevertheless within the range of expected outcomes, given the present level of global warming. Well, at least two of the three anomalies he examined — the Antarctic sea ice was still quite off the charts. (About those, one scientist told The Guardian that “something weird is going on”; another said that the abrupt changes were “very much outside our understanding of this system.”)

But even if, in most cases, the science is vindicated by this summer’s extremes, that isn’t ultimately all that reassuring. Forecasts for warming have long scared many of those who really looked at them, and so it’s not exactly comfortable to know that we are merely coasting along the high end of those forecasts today. As the climate stalwart Bill McKibben put it to me recently, when it comes to global warming, “‘I told you so’ are the four least satisfying words in the language.”

“The speed of us passing limits is mind-bending,” wrote the Texas A&M atmospheric scientist Andrew Dessler, with whom Hausfather shares a Substack, in a short reflection on why climate impacts seemed to be escalating so quickly. “When the Earth warms the next 0.1 degrees Celsius, an entirely new group of thresholds will be passed, bringing great harms to entirely different groups of people,” he wrote. “Many of them will not expect it, having been lulled into complacency by the fact that they hadn’t been negatively impacted by warming up to then. Is that you?”

As the extreme events have piled up this summer, I keep returning to a conversation I had last fall with the Texas Tech atmospheric scientist Katharine Hayhoe, a lead author of several U.S. National Climate Assessments and the chief scientist at the Nature Conservancy.

“The good news is we have implemented policies that are significantly bringing down the projected global average temperature change,” she said, describing a suite of projections now showing expected temperature rise this century of two to three degrees Celsius rather than four to five. But the bad news was that we had been “systematically underestimating the rate and magnitude of extremes.” Even if temperature rise is limited to two degrees, she said, “the extremes might be what you would have projected for four to five.”

In a long essay I published soon after that conversation, I emphasized that good news — that thanks to the technological and economic miracle of renewables, a global political awakening and an understanding that some earlier assumptions about future energy use were too pessimistic, we had about cut in half our expectations of warming in less than a decade.

This summer, I’ve been thinking more about her bad news — that even accounting for rapid global decarbonization and a drastic cut in expected global temperature rise, we may still end up in a world defined by impacts long called catastrophic. For now, it seems scary enough to say, we don’t really know.

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