The world does not have the luxury of waiting until coronavirus is “vanquished” to take action on the climate crisis, US special presidential envoy for climate John Kerry has warned.

He also said limiting temperature rises to 1.5C above pre-industrial levels – the threshold beyond which the most dangerous impacts of climate change are expected to be felt – requires urgent action by all major economies.

In a speech at the Royal Botanic Gardens, Kew, Mr Kerry said meeting the 1.5C limit will be impossible without China taking action, adding that the US and China had to work together to tackle the crisis.

In questions after his speech, Mr Kerry would not be drawn on whether the UK should approve new gas and oil exploration in the North Sea, but said the International Energy Agency has said there is no need for new fossil fuel projects and added “people have to measure the need very very carefully.”

He said the world was already seeing dramatic consequences of 1.2C of warming since pre-industrial times, pointing to floods in Germany, Nigeria and Uganda, and wildfires in Australia, western US and Siberia.

He painted a picture of political instability, failure of crops, extreme weather and billions of dollars of costs to protect major cities from rising sea levels and storms in coming decades without changing the path the world was on.

But investing in clean technology to drive down emissions presents the greatest economy opportunity since the industrial revolution, he said.

He said the pandemic still held too many people at risk of severe illness, hospitalisation and death, and while the development of vaccines were helping ease the crisis, the world was not through it.

But he warned: “I’m very sorry to say the suffering of Covid will be magnified many times over in a world that does not grapple with and ultimately halt the climate crisis.

“We don’t have the luxury of waiting until Covid is vanquished to take up the climate challenge,” he said.

He said the struggle to tackle the global climate crisis “is about protecting and preserving the fragile world we share, it’s about understanding that it costs more not to respond to the climate crisis than to it does to respond.

“And it is without exaggeration about survival.”

Drawing on the response by countries in the aftermath of the Second World War to rebuild the world, he said that “together we can solve humanity’s biggest threats”.

“The climate crisis is the test of our times, and while some may still believe it is unfolding in slow motion – no: this test is now as acute and existential as any previous one.”

And he pointed to young people forced to go on school strikes and protesting in the streets, saying: “they know the world is not responding fast enough to an existential threat they didn’t create, but for which they face bearing the ultimate burden: uninhabitable communities on an increasingly unliveable planet in their lifetimes”.

He warned: “You don’t need to be a scientist to know that what we’re looking at is a world no parent would ever be content to leave behind as an inheritance for future generations.”

The world had a narrow window to avoid that future, but had to cut emissions by at least 45% by 2030 to be on a credible path to reducing pollution to zero overall – known as net zero – by 2050.

“That makes this the decisive decade and it makes 2021 a decisive year, and most of all it must make Cop26 in Glasgow this year a pivotal moment to come together to meet and master the climate challenge.”

Speaking in the week that marks 100 days to the Glasgow summit, he said that after four years of absence from international climate action under Donald Trump’s presidency the US approached the challenge with humility, but with ambition – pointing to action President Joe Biden was taking.

He criticised countries that were still building coal plants and clear cutting forests, or allowing illegal deforestation and said: “we can’t afford a world so divided in its response to the climate crisis when the evidence is so compelling for action.”

He said the biggest step of the decade was scaling up the global clean energy economy, while there was also a need to develop and scale up emerging technologies, and invest heavily clean energy and energy efficiency.

And he warned there was “no way mathematically or ideologically to solve the climate crisis without the full cooperation or leadership” of China, and hoped the world’s biggest polluter would set out plans for near-term emissions for sectors.

“It’s not a mystery that the US and China have many differences but on climate cooperation, it is the only way to break free from the world’s current mutual suicide pact”, he warned.

Ahead of a G20 meeting of leading economies, he also said 1.5C could not be achieved without those nations, and the onus was on major economies who were the largest emitters of the past and today.

“My friends, there is still time to put a 1.5C future back in reach but only if every major economy commits to meaningful reductions by 2030, that’s the only way to put the world on a credible track to global net zero by mid-century.

“At or before Cop26 we need to see the major economies of the world not just set ambitious targets but we need to have clear plans over the next decade,” he said.