The gap between the promises nations made to cut carbon emissions and what scientists say is needed has left the world with just eight years to limit warming to the critical 1.5 degrees C, the United Nation's Environment Programme warned.

The agency's Oct. 26 report comes just days before world leaders gather in Glasgow, Scotland, on Oct. 31 for a high-profile global climate summit focused on halting ever-rising emissions and helping nations adapt to increasingly extreme weather. Under the 2015 Paris Agreement on climate change, 197 countries have committed to cutting greenhouse gas emissions to keep temperatures to "well below" 2 degrees from pre-industrial levels and ideally to 1.5 degrees.

But the new official pledges nations have made to the United Nations, along with promises that have not yet been recorded, will only shave 7.5% off projected 2030 emissions, the agency concluded. To keep the temperature rise to 1.5 degrees and avoid the worst impacts of climate change, a 55% cut would be needed, UNEP said.

Attention is now shifting to a G-20 meeting in Rome just ahead of the climate summit where the timeline for phasing out coal will be a contentious issue.

"The heat is on, and the leadership we need is off," United Nations Secretary-General António Guterres told reporters Oct. 26. "It's absolutely essential that all G-20 countries present before Glasgow [Nationally Determined Contributions, or NDCs] that are compatible with 1.5."

By the end of September, 120 countries that together account for 51% of global emissions had submitted new or updated such emission reduction pledges, known as NDCs, as required under the Paris accord. That leaves the world just over eight years to eliminate 28 gigatonnes of carbon emissions in addition to what the nations have already pledged to cut, UNEP said.

A narrow path remains

The lack of international resolve to make deep emissions cuts has climate experts worried, but they also believe the world can still meet the more ambitious Paris goal.

"The path is narrow ... but it's still possible," Helen Mountford, vice president of climate and economics at the World Resources Institute, told reporters Oct. 22. If G-20 countries "all went even further and set, and then achieved, ambitious 2030 targets and committed to net-zero by mid-century, we could actually be on a trajectory for 1.7 degrees C."

The U.K presidency of the upcoming climate summit, known as COP26, has a reason for setting a goal to "keep 1.5 degrees within reach" rather than aiming for the less aggressive 2 degrees warming target. That half-degree is significant, scientists say.

The loss of ice sheets in Antarctica and Greenland is projected to push sea levels more than 2 feet higher by 2100. But with 1.5 degrees warming, the sea level rise would be 0.3 feet lower than at 2 degrees and present less of a threat to low-lying coastal cities like Miami and New York City, a 2018 report from the Intergovernmental Panel on Climate Change concluded.

If nations meet the 1.5 degrees goal, 14% of Earth's population will suffer through severe heat waves at least once every five years, compared with 37% of people if warming is capped at 2 degrees, the panel found.

The economic impact would be widespread, too. U.S. gross domestic product, for example, would drop 1.2% for every degree that temperatures rise while inequality would rise, researchers have projected.

The UNEP report also lamented the fact that nations have invested just 17% of their pandemic recovery funds in projects that will reduce emissions. Separate findings by Columbia University's Energy Policy Tracker found that as of Oct. 20, G-20 nations had steered 40% of public money for energy in recovery packages to "fossil fuel-intensive sectors," compared with 37% to the clean energy sector.