The coronavirus lockdown hasn’t just slowed the march of COVID-19, it has reduced lethal air pollution and the associated mortality risks we usually take for granted. But when the lockdown lifts, those risks of the status quo might not just return to normal—they might worsen—as governments weaken environmental regulations and pour billions of dollars into polluting industries.

"I think that in the long run this crisis will be a disaster for the climate," said Francois Gemenne, director of The Hugo Observatory, a Belgium-based research center. "Of course there are short-term effects on the environment: a substantial drop in air pollution, a fall in greenhouse gas emissions, etc. But in the long term, these temporary effects will probably be insignificant."

Air pollution, which causes an estimated 7 million deaths annually, has plunged worldwide during the coronavirus lockdown as factories have closed, power demand dropped, and traffic evaporated.

The European Space Agency and NASA have documented drops in lethal pollution of 40 percent to 70 percent. One Stanford professor projected that China’s two month lockdown saved up to 77,000 lives of children and the elderly—a number that dwarfs the 3,100 killed by the coronavirus in that country over the same period.

Lethal air pollution comes from the same sources—power plants, factories and vehicles—as many greenhouse gases. The Centre for Research on Energy and Clean Air estimates China’s lockdown reduced its CO2 emissions 25 percent.

Those numbers seem to bode well for the climate and climate-related mortality risks. The Climate Impact Lab has projected climate mortality from status-quo emissions at 1.5 million additional deaths per year by 2100.

But Gemenne pointed to aspects of this economic restart that portend a worsening climate scenario:

• Emissions tend to bounce back after an economic collapse, as they already have in China, and as they did in 2008-09. Some call this the "rebound effect" or "revenge pollution." Lauri Myllyvirta, lead analyst for the Centre said, "The obvious point to make here is that China’s ‘airpocalypse’—the horrendous smog of the winter 2012-13—was a direct outcome of the smokestack stimulus started in 2008."

• Governments are reviving their fossil-fuel industries and supporting polluters like airlines instead of advancing low-carbon alternatives.

• Some governments, including the United States, are suspending enforcement of environmental regulations, unleashing polluters, and others are using the pandemic as an excuse to renege on climate pledges.

• Climate activists may be shooting themselves in the foot by promoting the politically unpalatable idea that the climate crisis demands a similar economic shutdown.

"Above all, climate change is not a ‘crisis,’" Gemenne said, "it is an irreversible transformation. There will be no going back to normal, no vaccine. There is a need for structural measures, not short-term ones."

As a result of the pandemic, he told me in an exchange of tweets, "For climate change, we can indeed assume impacts will get worse (including disasters), resulting in increased mortality in the long-run."

The most positive effect the pandemic might have on climate, Gemenne said, is if it affects the outcome of the U.S. presidential election.

University of Exeter Geography Professor Neil Adger agreed with Gemenne’s realism on the pandemic’s relation to the climate, and suggested some more silver linings: "practices around community, reality of unnecessary travel, and other trends show another future is possible and desirable."