It is a familiar refrain to anyone who works on climate change, and it is why global efforts to slow down warming offer a cautionary tale for the effort to slow down the pandemic.

“Both demand early aggressive action to minimize loss,” said Kim Cobb, a climate scientist at the Georgia Institute of Technology who was teaching classes remotely this week. “Only in hindsight will we really understand what we gambled on and what we lost by not acting early enough.”

Scientists like Dr. Cobb have, for years, urged world leaders to bend the curve of planet-warming emissions. Instead, emissions have raced upward. Now the consequences are being felt: a three-month-long flood in the Florida Keys, wildfires across a record hot and dry Australia, deadly heat waves in Europe.

Gernot Wagner, a climate economist at New York University, called the virus “climate change on warp speed.”

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Why have we not taken climate risks to heart? Politics and psychology play a role.

Change is hard when there’s a powerful industry blocking it. The fossil fuel industry has pushed climate science denial into the public consciousness. It has lobbied against policies that could rein in the emissions of planet-warming gases. And, it has succeeded: The United States, history’s biggest emitter of greenhouse gases, is the only country in the world to have withdrawn from the Paris accord, designed to stave off the most catastrophic effects of climate change.