António Guterres, the U.N. secretary general, opened the conference with a blistering critique of the world’s failure to unite to address global warming.
With humanity already struggling to cope with rising seas, more powerful storms, deadly heat waves and rapidly changing ecosystems needed to sustain life, the global climate summit in Glasgow opened on Monday with a series of speeches that amounted to desperate pleas for action from nations large and small.
“Climate change is already ravaging the world,” President Biden said in a speech at the summit, known as COP26, on Monday afternoon. But even while global warming is causing widespread economic damage and upending lives, he said this was also a moment of opportunity to reshape the way humans live in better harmony with nature.
“We are standing at an inflection point in world history,” he said, calling climate change an “existential threat to human existence as we know it.”
“None of us can escape the worst that is yet to come if we fail to seize this moment,” he said.
Underscoring the urgency of the moment, with leaders of more than 120 countries gathered for the summit, the United Nations secretary general, António Guterres, said that the effects of a warming planet were being felt “from the ocean depths to the mountaintops.”
“Sea level rise has doubled from 30 years ago,” he said. Oceans are hotter than ever, parts of the Amazon rain forest emit more carbon than they absorb, and in the last decade about four billion people were affected by events related to the changing climate.
“Enough of burning and drilling and mining our way deeper,” Mr. Guterres said. “We are digging our own graves.”
The conference’s aim is to prevent the average global temperature from rising more than 1.5 degrees Celsius compared with levels before the Industrial Revolution. That is the threshold beyond which scientists say the dangers of global warming — such as deadly heat waves, water shortages, crop failures and ecosystem collapse — grow immensely.
But Mr. Guterres said the idea that humanity is making enough progress was “an illusion.” He called on countries not to return to the summit every year to revisit their climate targets, but to take the opportunity to nudge one another on “until keeping to 1.5 degrees is assured, until subsidies to fossil fuels end, until there is a price on carbon and until coal is phased out.”
Many countries will press against such specific measures, and the absence of leaders from Russia and China from the meeting cast doubts on how united the world can be in the struggle.
China, the world’s largest greenhouse gas emitter, proposed a new emissions target that is largely indistinguishable from one it made six years ago. The United States, the largest historic emitter, has an ambitious emissions goal but has not been able to pass legislation to achieve it. And Australia, India and Russia have not made any new pledges to draw down climate pollution this decade.
Meanwhile, only a few wealthy countries have allocated money to help poor and vulnerable nations cope with the effects of climate disasters that those countries have done little to cause.
Those two factors make the likelihood of success at the conference, known as COP26, uncertain.
Prime Minister Boris Johnson of Britain kicked off the summit with an urgent call for action, likening climate change to a bomb primed to explode, even as he acknowledged the challenges ahead.
“The tragedy is that this is not a movie and the doomsday device is real,” he said. “Humanity has long since run down the clock on climate change. It is one minute to midnight on that doomsday clock, and we need to act now.”
The prime minister of Barbados, Mia Mottley, poked holes in the climate promises of some countries that are based on technologies that don’t yet exist.
“This is at best reckless,” she said, and “at worst dangerous.”