A single year’s temperature readings do not constitute a trend. But there is a trend. The five warmest years have come in the past five years. Eighteen of the 19 warmest years on record have come since the beginning of this century. That 2018 did not quite match the record-setting 2016 for warmth is in part because a warming El Niño effect in 2016 raised temperatures even higher than human influence alone would have. By contrast, 2018 saw a cooling La Niña and was still fourth-warmest. The overall direction is relentless: This decade will be warmer than the last, which was warmer than the one before it, and so on.

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As more and more of their predictions have come true, scientists have become more confident in their models — and more alarmed. Some effects of climate change remain difficult to predict or plan for. Warming could even contribute to cold snaps such as the one that prompted Mr. Trump to mock climate science on Twitter last week. Other effects are all too predictable: rising seas, stronger storms, more heat waves, more droughts, more flooding, invasive species, the proliferation of disease, depleted fisheries, dying ecosystems, more acidic oceans, crop failures, mass migrations, days so hot that people cannot work. Experts warn that Americans are already likely feeling global warming’s influence in the super-wet storms that have pummeled places such as Houston, feeding on extremely warm waters in the Gulf of Mexico.

In the face of ever-rising evidence, the president did not even mention climate change in Tuesday’s State of the Union address. His administration still intends to remove the United States from the Paris climate agreement, the world’s best hope to get all major contributing countries moving in the same direction. While the Trump administration ripped up clean-air rules, U.S. greenhouse-gas emissions shot up 3.4 percent last year, putting the lie to the argument that market forces alone will adequately drive down the country’s carbon footprint.

Some Democrats, meanwhile, have announced a “ Green New Deal” whose goal seems to be radically reshaping U.S. society and vastly expanding government rather than simply addressing the climate problem, which is hard enough — and important enough. Though not nearly as harmful as Mr. Trump’s rank denialism, engaging in this sort of fantasy also hurts the cause of practically addressing the issue.

The world needs rational U.S. leadership. Unfortunately, global warming will not stop in the meantime.