Americans should get used to terms such as “heat dome” and “megadrought.” The sorts of extreme weather events that experts warned would become increasingly frequent are occurring. Searing temperatures across the Pacific Northwest are just the latest example.

Temperatures have been 30 to 40 degrees higher than usual in that typically temperate area. Heat records across the Pacific Northwest are being broken — not by a degree or two, but by four or five. Canada saw the highest temperature ever recorded anywhere in the country. Hotels with air-conditioned rooms are booked solid. State and local authorities have relaxed covid-19 rules to pack more people into cooling centers. Heat deaths have spiked. The heat wave’s effects on wildfires and agriculture may not yet be fully visible. Cherry growers are rushing to harvest their crop before it shrivels in the sun — but stopping their picking at lunchtime to avoid the baking heat. Vegetation may dry out more than usual, creating tinderbox-like conditions.

This is all occurring before July, the month in which cities such as Seattle had previously recorded rare triple-digit temperature readings. It also appears to reflect a dangerous underlying trend; extreme heat days have doubled in the area in less than a century.Experts project that the number will continue to spike over the coming decades. Nor has the perilous weather been contained in the Northwest. Areas across the western United States have seen new temperature records set this year. Drought is also punishing the West. As coastal zones cool back down, areas farther east are getting baked.

It will take scientists more time to attribute this particular episode to climate change. Specifically, experts are still debating whether global warming promotes the formation of high-pressure heat domes such as the one that has trapped hot air near the ground in Oregon and Washington state. But it is already clear that baseline temperatures that seem only mildly higher produce more extreme events, more often. Even if it were bound to happen, this heat wave likely would have been more bearable before all that extra energy was added to the system. And even if the heat would still have been punishing in this case, this disaster illustrates viscerally the sorts of events that global warming will undoubtedly spur.

States such as Oregon and Washington are not built for heat. Many people do not have air conditioning. Hospitals are unused to handling symptoms of extreme heat exposure. Similarly, the dry docks in Virginia’s Hampton Roads were built for a lower sea level, and the fisheries in Maine rely on water temperatures remaining within a certain range. Human society has developed within a narrow temperature band. Coping with the warming that is already on its way, because of the long-lived greenhouse gases humans have already pumped into the atmosphere, will be a long and expensive project. The sooner the world weans itself off carbon-emitting forms of energy, the better chance human beings have of preventing widespread suffering.

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