"All of the science suggests that peaking by 2020 is critical," said Kelly Levin, an analyst with the World Resources Institute and one of the report's lead authors. "If you miss that, we rely on much steeper reductions in the future."
Moreover, the report finds that the gap between countries' Paris promises and emissions levels that would be needed to stay consistent with the Paris agreement is even larger than previously believed.
Because of all of this, the report says, the stakes are now higher. "Concerns about the current level of both ambition and action," it says, are now amplified in comparison with previous years.
Here's why. Current global emissions were 53.5 billion tonnes of carbon dioxide equivalents in 2017; if all countries live up to all promises made in Paris, they would also be about 53 billion tonnes in 2030. (Emissions are projected to grow with the growth of populations and economies, so basically, under the current Paris promises, the world is running simply to stand still.) This sets the world on a path to about 3C of total warming by 2100.
Hence the gap. Emissions can only be about 40 billion tonnes annually in the year 2030 to preserve good odds of holding warming to 2C, the UNEP report finds. And for 1.5C, they would have to fall to just 24 billion tonnes or so by that year - an extraordinarily steep plunge.
In a middling scenario that is also consistent with the Paris agreement's language but takes more risk with the planet - holding warming below 1.8C - emissions would have to fall to about 34 billion tonnes by 2030.
The Earth has already warmed about 1C above preindustrial temperatures, as recorded in the latter part of the 19th century. And because that figure is a global average, some areas - especially the Arctic - are already considerably warmer than that.
Current actions by major emitting countries - all of whom agreed in 2015 to be part of the Paris climate agreement, though the United States is now backtracking - aren't nearly enough to prevent another half degree or more of warming, the report finds. "We need three times more ambition to close the 2degree gap, and five times more ambition to close the 1.5degree gap," said Drost.
In calling for dramatically more action in a very short period of time, the new document matches the dire verdict reached last month by scientists who are part of the UN's Intergovernmental Panel on Climate Change.
Their report concluded that global emissions must be sharply cut, and that this must happen in just 12 years, by 2030 to preserve a chance of limiting temperatures to a rise of 1.5C.
But the new UNEP document presents considerably more direct policy analysis and perhaps even some finger-pointing. The document goes through G20 member nations one by one, listing which ones are failing to live up to the promises they made in Paris three years ago (promises that, themselves, are far too little to keep the planet's warming in check). Together, the G20 countries account for 78 per cent of the globe's emissions.
Seven of these countries - Argentina, Australia, Canada, the Republic of Korea, Saudi Arabia, South Africa and the United States - are off track to meet their Paris promises for the year 2030, the UNEP report finds. So is the entire European Union.
Several other G20 countries - Russia, India and Turkey - are already on course to exceed their Paris promises by a good measure, but the report questions whether this may in part because they have aimed their ambitions too low.
For two more G20 countries - Mexico and Indonesia - it just isn't clear where they are with respect to their goals. And even for those few countries that are on target - Brazil, China Japan - there's plenty to worry about. For example, Brazil has just elected a populist leader, Jair Bolsonaro, who some fear will enact policies that could lead to further deforestation of the vast Amazon rain forest and, therefore, far larger greenhouse gas emissions from Brazil.
In light of all this, it's little surprise that global emissions ticked upward again last year after three years - 2014 through 2016 - during which they appeared to flatten out. That brief hiatus for rising emissions now appears to have been a blip. Overall, the world continues to move in the wrong direction, and, as the G20 analysis shows, the blame can kind of be spread around.
"Rich countries need faster reductions; the poorer countries need to slow down the growth," said Glen Peters, research director of the Centre for International Climate Research in Oslo and a report author. "No one is doing enough."
