(Bloomberg) -- The world has refused to slash its collective greenhouse gas emissions, narrowing the planet’s pathway back to a safe climate.

Authors of an annual United Nations Environment Program (UNEP) report published Tuesday were uncharacteristically direct in their 2019 assessment of the gap between actual and desirable emissions levels.

“The summary findings are bleak,” they write. “Countries collectively failed to stop the growth in global GHG emissions, meaning that deeper and faster cuts are now required.”

How deep and how fast? Nations must halve their 2018 pollution levels by 2030 to meet the Paris Agreement goal of limiting heating to 1.5 degrees Celsius. Global emissions have risen about 1.5% a year in the last decade, plateauing between 2014 and 2016.

The new report is part of a larger trend among high-profile scientific assessments published in the last 18 months, each featuring increasingly blunt language from a community not known for it. Examples include three studies from the UN-backed Intergovernmental Panel on Climate Change. They addressed limiting global heating to 1.5 degrees Celsius, how land is changing around the world and the effects of higher temperatures on iced areas and oceans.

This latest research—the tenth edition of the annual Emissions Gap report—is a hard-check on sentiment, said Leah Stokes, assistant professor of political science at the University of California, Santa Barbara. Current policies could lead to 60 billion metric tons of climate pollution in 2030. To have a shot at staying below 1.5 degrees, that figure needs to be 25 billion tons.

“That’s easy math,” she said. “We’re double what we need to be.”

Of course, “bleak” doesn’t mean hopeless, the researchers said. Political and civic attention to climate change is increasing, led in many nations by younger citizens. Renewable energy is the cheapest source of power in much of the world and new utility-scale systems can already compete with the marginal operating costs of existing coal plants.

Countries know what they need to do, even if they’re not yet doing it. In 2009, G20 nations agreed to phase out fossil-fuel subsidies, although none have actually set a deadline for doing so. Despite scientists’ pleas to zero-out emissions by mid-century, only a few nations—and none in the G20—have given the UN climate administration a timeline for achieving it.

There’s still a path to climate safety, and most of it runs through those G20 countries, since they make up almost 80% of emissions. As a group, the world’s biggest economies are likely to meet 2020 climate pledges made in 2010—though with the notable exception of, among others, the U.S., Canada and Mexico.

The new report breaks out specific recommendations for seven key emitters: the U.S., Australia, Brazil, Canada, Japan, South Korea and South Africa.

China, said the UN, should ban all new coal-fired power plants—despite last week’s news that the country is still on a coal-plant binge) and make electricity carbon-free. The U.S. should regulate power plants, introduce carbon pricing and decarbonize its buildings and transportation systems, the UN says—but the realities of domestic politics in America make that unlikely.

Indeed, the report makes clear that the time for half-measures has passed.

“Incremental changes will not be enough, and there is a need for rapid and transformational action,” the authors write. Climate-proofing the global economy “will require fundamental, structural changes” along with “investments in defensive and adaptive infrastructure” and a massive shift in “values, norms, consumer culture and world views.”

Those changes will require at least $1.6 trillion in energy-sector investment annually through 2050, they estimate. That’s $48 trillion.

Astonishingly, some nations are still increasing their plans for fossil-fuel production, making an already bad situation worse. The UNEP last week issued its first Production Gap Report, a related initiative that looks at the scale of fossil-fuel resources nations can or expect to develop. Overall, the world may produce 50% more coal, oil and gas than is compatible with a 2 degree Celsius scenario, and 120% more than a 1.5 degree scenario requires.

“The climate problem is mainly a fossil-fuel problem” rather than an emissions problem, said Peter Erickson, a senior scientist at the Stockholm Environment Institute and contributor to the production-gap report. “In the long-term, it may be better to talk about it that way.”

To contact the author of this story: Eric Roston in New York at eroston@bloomberg.net

To contact the editor responsible for this story: Joshua Petri at jpetri4@bloomberg.net, David Rovella

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