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Crop yields are declining. Tropical diseases like dengue fever are showing up in unfamiliar places, including in the United States. Tens of millions of people are exposed to extreme heat.

These are the stark findings of a wide-ranging scientific report that lays out the growing risks of climate change for human health and predicts that cascading hazards could soon face millions more people in rich and poor countries around the world.

The report, published Wednesday in the public health journal The Lancet, incorporates the work of 24 academic institutions and United Nations agencies and follows a major climate assessment issued last week by the United States government. The two studies represent the most serious warnings to date that climate change is posing a series of interconnected health risks for the global population.

“We don’t see these health impacts individually,” said Kristie L. Ebi, a professor of global health at the University of Washington and one of the authors of the Lancet study. “We see them jointly. We see them coming at communities all at the same time.”