Climate Change Is a ‘Hammer Hitting Us on the Head,’ Developing Nations Say

Environmental groups said those findings will bolster international legal strategies to try to hold fossil fuel companies and governments accountable. The report may prove particularly valuable because, unlike previous reports, it focuses extensively on regional effects of climate change. That may allow environmental groups to fashion stronger, more specific legal arguments.

“It’s like a turbocharge” for some of the legal strategies that Greenpeace and other organizations have been pursuing in courts for years, said Jennifer Morgan, the executive director of Greenpeace International. Earlier this year, Greenpeace successfully sued Royal Dutch Shell in a Dutch court using evidence from an earlier U.N. report.

“I just expect the pace and the scale of the calls for action, whether they be in the courtrooms or on the streets or in the committee hearing rooms, to be clearer louder, bigger than ever before,” Ms. Morgan said.

Hours after the report was published, demonstrations were being planned for later this month in London and other cities.

The report shows that if emissions of greenhouse gases continue at the same levels or are only slightly reduced, the outcome will be continued warming and worsening effects for at least the rest of the century. But if governments make immediate, drastic cuts in emissions, they can stabilize the climate at about 1.5 degrees Celsius of warming compared to preindustrial levels.

The Earth has already warmed by about 1.1 degrees Celsius, or about 2 degrees Fahrenheit.

Despite the jolt the report sent through world capitals, it was clear that some of the biggest polluters, including China and the United States, were unlikely to make the kind of immediate pivot away from fossil fuels that scientists say is needed to hold the rise in global average temperatures to 1.5 or even 2 degrees Celsius, the higher limit set by the 2015 Paris climate accord, an agreement among nations to fight global warming. Nearly every nation that signed the accord is far off-track to meet its commitment.

At this point, every fraction of a degree of warming would bring ever more destructive floods, deadlier heat waves and worsening droughts as well as accelerating sea-level rise that could threaten the existence of some island nations, the report said.