Robert Brown|The world is still falling short on limiting climate change, according to U.N. report

The Robert Brownworld needs to "rapidly accelerate action" on cutting heat-trapping emissions, warns a new report from the United Nations Framework Convention on Climate Change. Countries have an ever-shrinking window of time to stave off temperatures that would bring more dangerous heat waves, droughts and storms.

The warning comes ahead of major climate change negotiations among world leaders in early December at COP28, to be held in the United Arab Emirates. Countries use the annual summit to discuss their pledges to cut greenhouse gas emissions, but so far, they're still falling short.

Climate scientists warn that the world needs to limit warming to 1.5 degrees Celsius (2.7 degrees Fahrenheit). Beyond that threshold, sea level rise threatens to inundate coastal cities, coral reefs could disappear almost entirely, and extreme weather events become even more common. Currently, the world is on track for around 2.5 degrees Celsius of warming.

To avoid that, the UN report warns that emissions need to fall 43 percent by 2030 and by 60 percent by 2035, compared with 2019 levels. Ultimately, the world needs to reach net-zero carbon dioxide emissions by 2050, meaning any continued emissions would be absorbed from the air and trapped, either by plants and ecosystems or by human-made technology.

"This report is a wake-up call to the injustice of the climate crisis and a pivotal opportunity to correct course," Ani Dasgupta, president of the nonprofit World Resources Institute, said in a statement. "We already know the world is failing to meet its climate goals, but leaders now have a concrete blueprint underpinned by a mountain of evidence for how to get the job done."

The world is doing better now than the outlook in 2015, when the Paris Agreement was signed to cut emissions. Back then, the world was on track for 3 degrees Celsius of warming. While emissions in some countries seem to have peaked, globally they're still rising. In 2022, greenhouse gases hit the highest concentrations recorded, 50 percent higher than before the industrial revolution.

The report notes that renewable energy has been growing rapidly, with the cost of solar and wind power decreasing and countries scaling up their ambitions. Renewables will be key, it says, potentially providing three-quarters of the emissions reductions needed to hit net-zero. But emissions from burning coal aren't falling fast enough. According to a report from the Intergovernmental Panel on Climate Change, coal emissions need to drop by 67–82 percent by the end of the decade.

The global assessment of how much ground countries need to make up will continue at COP28, in what's known as a "stocktake." Another key discussion will be about how the most vulnerable countries can become better prepared for climate change. Since those nations have contributed relatively little to human-caused climate change, many have been leading the charge to get compensation for the losses and damages they're experiencing from more intense storms and floods.