The US Special Envoy for Climate John Kerry gave a dire warning to the world over the urgency of addressing the climate crisis in a speech at Kew Gardens yesterday (Tuesday, July 20).

The former Secretary of State and Presidential candidate told assembled scientists and journalists that the window for preventing the worst, catastrophic impacts of the climate crisis was closing as he sought to ramp up momentum ahead of the crucial COP26 climate summit in Glasgow later this year.

Kerry symbolically gave his remarks under the glass dome of a greenhouse at Kew in sweltering heat, while outside climate activists from Extinction Rebellion (XR) held placards urging him and the United States to 'Act Now' and rapidly decarbonise to global economy.

"The climate crisis is the test of our own times," Kerry said in his speech.

"This test is now as acute and as existential as any previous one. Time is running out," he added.

Kerry warned that current pledges from nation states around the world, despite political allusions to the contrary, were in no way sufficient and signalled that the Earth was on course for temperature increases of 2.5 or 3 degrees Celsius

"We’re already seeing dramatic consequences with 1.2C of warming. To contemplate doubling that is to invite catastrophe," Kerry said.

His words alluded to many reports that have detailed the likely devastating impacts warming of 2.5-3 degrees Celsius would have on human beings and the Earth's wider ecosystems.

One such report found that hundreds of millions of people living in coastal cities would likely be displaced in the coming decades, while others have predicted widespread global food shortages amid worsening crop failures.

After his speech, Kerry was pressured by journalist's including Channel 4's Krishnan Guru-Murthy on the actions of US President Joe Biden's government to date, which has approved over 2,100 new oil drilling permits on federal land in the US since the president's inauguration on January 20.

Amid Kerry's appearance at Kew Gardens, activists with Richmond XR staged a "peaceful vigil" outside Kew Gardens in the hopes of putting pressure on the US Climate Envoy to convert his strong words into action.

"Extinction Rebellion stands in solidarity with indigenous peoples and all those on the frontlines of the climate crisis around the world.

"The United States and the United Kingdom must demonstrate true climate leadership ahead of crucial negotiations at COP26 by ending support for all fossil fuel projects," a statement from the group on Kerry's speech read.