The world is heating up, and there are no “credible natural explanations for this amount of warming.” U.S. greenhouse-gas emissions have decreased a bit lately. But they need to go down much further and faster to avoid dire consequences.

Already, the nation is seeing “intensifying droughts, increasing heavy downpours, reducing snowpack,” as well as “declines in surface water quality.” Without a course change, increasingly depleted groundwater, rising seas and other effects will make it more difficult to farm and provide enough water for large cities.

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Foodborne and waterborne diseases will spread. Disease-carrying ticks and mosquitoes will be more common. Extreme heat will cause more deaths. Wildfires and insect infestations will overwhelm U.S. forests. Sea ice will melt and coral reef ecosystems will dissolve. Power outages and fuel shortages will be more frequent. Roads and bridges will swamp. Pipelines will become unsafe. Waterside property will be increasingly unusable. Fisheries will dwindle.

“Even if significant emissions reductions occur, many of the effects from sea level rise over this century — and particularly through mid-century — are already locked in due to historical emissions,” the report explains, underscoring the necessity for coastal communities to prepare. On the horizon is “the potential need for millions of people and billions of dollars of coastal infrastructure to be relocated.”

Critics of acting on climate change often cite the possible economic costs. But not acting has costs, too. The experts expect “substantial net damage to the U.S. economy throughout this century,” finding that “with continued growth in emissions at historic rates, annual losses in some economic sectors are projected to reach hundreds of billions of dollars by the end of the century — more than the current gross domestic product (GDP) of many U.S. states.”

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And the damage will be long-lasting. “The climate change resulting from human-caused emissions of carbon dioxide will persist for decades to millennia. Self-reinforcing cycles within the climate system have the potential to accelerate human-induced change and even shift Earth’s climate system into new states that are very different from those experienced in the recent past,” the report notes.

The White House responded to the report by misrepresenting scientists’ work and promising “fuller information” in the next analysis. Cooking the next report will not change the facts. Mr. Trump and the Republican Party have been negligent stewards of the country’s irreplaceable resources. Future Americans will not forgive or forget what these “leaders” did to them. Playing games with report release schedules won’t change that.