November 3, 2021: -On Monday, U.K. Prime Minister Boris Johnson warned world leaders at the COP26 climate summit that it is “one minute to midnight” in the race to prevent global heating from surpassing a critical threshold.

The U.K. hosts U.N.-brokered climate talks in Glasgow, Scotland, in what is described as humanity’s last and best chance to secure a livable future. For this reason, the long-awaited summit is seen as the important diplomatic meeting in history.

“Humanity has since run down the clock on climate change,” Johnson said at the World Leaders Summit Opening Ceremony. “It’s minute to midnight on that doomsday clock, and we need to act now.”

The COP26 summit, opening formally on Sunday and running through to November 12, comes six years after the landmark Paris Agreement was signed by around 200 countries to limit the growing global temperatures to 2 degrees Celsius above pre-industrial levels and to “pursue efforts” to cap which heats to 1.5 degrees Celsius.

The latter threshold is a crucial global target because so-called tipping points become more likely beyond this level. Tipping points refer to an irreversible change in the climate system, locking in global heating.

To have the chance of capping global heating to 1.5 degrees Celsius, the aspirational goal of the 2015 Paris climate accord, the world needs almost to halve greenhouse gas emissions in the next eight years and reach net-zero emissions by 2050.

The U.N. warned the world is on a “catastrophic pathway” to 2.7 degrees Celsius of heating by the century-end.

On Monday, the U.K. prime minister will also echo his call for world leaders to move from talk and debate to concerted action “on coal, cars, cash, and trees.”

Johnson said, “We need to get about climate change, and the world should know when that’s going to happen.”

On Monday, U.S. President Joe Biden, European Commission President Ursula von der Leyen, and Australian Prime Minister Scott Morrison are set to deliver speeches to assembled delegates.

Chinese President Xi Jinping will not be taking part in COP26, but a written statement will be published later in the day.

Diplomats and world leaders, including Johnson, have sought to downplay expectations of success in the run-up to the summit. However, countries representing more than half of the world have insisted there can be “no more excuses for unfulfilled promises” in Glasgow.

Johnson, who has previously expressed skepticism about the climate crisis, told BBC TV on Sunday that he estimated the chances of a successful outcome at COP26 at roughly six out of 10.

The U.K. published its repeatedly delayed net-zero strategy last month. It was seen as a critical test as the country prepared to preside over COP26, although critics have suggested it decreases short on meeting the climate emergency demands.