People in Chinese cities usually plagued by harmful air pollution are breathing far cleaner air . Boat‑free canals in Venice, Italy, are clear enough to see fish. And for the quarter of the global population now living under a coronavirus lockdown, a lack of cars and planes has made the world quieter and birdsong more apparent.

While there are signs of easing pressure on the environment , no credible environmentalists say the response forced by the pandemic is a solution for the challenges the world faces on climate …