Greta Thunberg has urged people around the world to choose a “new way forward”, as she joined calls for a combined effort to tackle coronavirus and the climate crisis.

Dramatic improvements in air and water quality as coronavirus lockdowns have cut pollution have prompted calls for a low-carbon future, but the need to get millions back to work is clouding the picture for the future.

The Swedish climate activist, taking part in a streamed event to mark Earth Day, said the extraordinary measures to stop the spread of the novel coronavirus did not mean the climate crisis had gone away.

“We need to tackle two crises at once,” she said.

The teenage campaigner was filmed at the Nobel Prize Museum in Stockholm in digital conversation with Johan Rockström, the earth systems scientist and director of the Potsdam Institute.

“Whether we like it or not the world has changed, it looks completely different from how it did a few months ago and it will probably not look the same again and we are going to have to choose a new way forward,” the teenager said.

Every day is #EarthDay.
The changes needed to safeguard future living conditions for all species won’t come from governments or businesses.
It will come from the best available science and public opinion.
So it’s up to us.
Spread the science. #unitebehindthescience pic.twitter.com/6nIFpz1Qf3

— Greta Thunberg (@GretaThunberg) April 22, 2020

With economies round the world shut down, wildlife has returned to some city streets, with wolves, deer and kangaroos spotted on thoroughfares usually teeming with traffic.

Fish have been seen in Venice canals no longer polluted by motor boats, while residents of some Indian cities have reported seeing the Himalayas for the first time in decades.

Satellite imagery has shown significant air quality improvements across Europe and Asia, including China, where the coronavirus pandemic emerged at the end of last year.

Residents in some of China’s most smog-prone cities said they feared blue skies would not last as the world’s second biggest economy got back to work, however.

Climate activist Greta Thunberg on the 50th anniversary of Earth Day says during crises whether it’s coronavirus or climate crisis, it is important to listen to the scientists pic.twitter.com/1VW03oCMll

— TRT World Now (@TRTWorldNow) April 22, 2020

UN chief Antonio Guterres echoed Ms Thunberg, urging governments to use their economic responses to the pandemic to tackle the “even deeper emergency” of climate change.

With battle lines emerging between investors backing “green stimulus” measures and industry lobbyists aiming to weaken climate regulations, Mr Guterres cautioned governments against bailing out heavily polluting industries.

“On this Earth Day, all eyes are on the COVID-19 pandemic,” Mr Guterres said.

“But there is another, even deeper emergency, the planet’s unfolding environmental crisis.”

The coronavirus pandemic is expected to drive carbon dioxide emissions down 6 per cent this year, the head of the World Meteorological Organisation (WMO) said, in what would be the biggest yearly drop since World War II.

But that’s not enough to stop climate change, the WMO said.

“COVID-19 may result in a temporary reduction in greenhouse gas emissions, but it is not a substitute for sustained climate action,” the WMO said in an Earth Day statement.

-with agencies