People walk on the Champs-Elysees during a car-free day in central Paris in 2015.
People walk on the Champs-Elysees during a car-free day in central Paris in 2015. Philippe Wojazer/Reuters

City-level solutions, including banning vehicles from the streets, have helped dozens of nations speed toward a greener future. But will they be enough?

The central goal of the Paris Agreement is to keep global temperatures from rising more than two degrees Celsius above pre-industrial levels. It's an ambitious goal, and one that the 196 parties to the deal are still trying to figure out how to accomplish. Thousands of delegates from all over the world are meeting in Bonn this week to continue resolving the details for implementing the agreement, but one thing the initial accord does specify is that global greenhouse gas emissions should peak “as soon as possible.”

That’s because the longer we allow emissions to keep climbing, the harder it will be to prevent catastrophic warming. Indeed, our best shot at keeping temperature increases below two degrees is to have global emissions collectively peak by 2020. What’s less clear is whether or not we'll make it.

In a new report out today from the World Resources Institute, researchers took stock of every country’s progress toward peak emissions thus far, and their commitments to peak emissions in the future. “It's sort of a glass-half-full, glass-half-empty picture,” says David Rich, a senior associate at WRI and co-author of the new study.

Let's start with the good news, since it’s so rare in climate coverage today. Rich and his co-author, Kelly Levin, reviewed historical emissions and found that the number of countries whose greenhouse gas emissions have already peaked is on the rise. In 1990, 19 countries had already peaked; by 2000, that number had risen to 33, and by 2010 it was 49—including France (which peaked back in 1991), the Netherlands (1996), Australia (2006), and the United States (2007). “Nearly all of the developed countries have already peaked. That's an encouraging trend,” Rich says. “People may not know that, based on the current rhetoric, but actually [U.S. emissions] did peak 10 years ago. We’ve made a lot of progress, and our economy has grown.”

The team analyzed countries’ future climate pledges under international agreements established in Copenhagen, Cancun, and Paris, and found that another four countries will likely peak by 2020 and then four more by 2030—if they live up to their commitments laid out in INDCs—bringing the total up to 57.

Still, the total number of countries that have peaked matters less than their share of global emissions. To illustrate: Between 1990 and 2000, the number of countries that peaked grew by 14, but their share of global emissions actually decreased—from 21 percent to 18 percent—over the same period. Sharper emissions cuts by some countries, especially powerhouse emitters, could offset slower peaks by others. By 2010, the 48 countries that had peaked were responsible for 36 percent of global emissions. The countries that have peaked could account for 40 percent of emissions by 2020, and 60 percent by 2030.

Of course, that's assuming that, despite the Trump administration's best efforts to revive America’s coal and oil industries and the president's promise to pull the U.S. from the Paris Agreement, U.S. emissions won’t rebound past the 2007 peak.

If we don’t count the U.S., countries that have peaked would account for just 26 percent of global emissions by 2020, down from 40 percent, and just 46 percent in 2030, down from 60 percent. Fortunately, that's an unlikely scenario: Market forces and commitments from state-, county-, and city-level officials are likely to keep U.S. emissions below 2007 levels, according to Rich and Levin.

Now for the bad news: All this progress is still probably not enough to limit warming to less than two degrees over pre-industrial levels. “The global picture is still not good,” Rich says. “Global emissions need to peak in 2020 for what's called the least-cost likely chance of meeting the two-degree global temperature target, and we're not on track for that.” Even if every nation meets all the commitments in its Paris Agreement pledges, global emissions are still expected to increase between 2020 and 2030. That doesn't necessarily mean that the goals of the Paris Agreement are totally out of reach, but it will be a lot harder—not to mention more expensive—to get there. Global emissions can peak later, but it means countries will have to decarbonize faster, and may have to rely on as-yet unproven carbon-capture technologies to limit global warming to safe levels.

And this is where the U.S.’s waffling on climate action could really be a burden. It's too soon to tell what effect the current administration's climate policies—or lack thereof—will have on U.S. emissions reductions. But given that the U.S. is second only to China in terms of annual emissions, reneging on its pledge to cut its emissions by another 26 to 28 percent below 2005 levels by 2025 could seriously delay the global emissions peak.

Rich hopes these findings can serve as “another push to ramp up ambition and ramp up mitigation across both developed and developing countries so we can meet the global temperature goal.”

This story originally appeared as “What Are Peak Emissions and Why Should You Care?" on Pacific Standard, an editorial partner site. Subscribe to the magazine in print and follow Pacific Standard on Twitter to support journalism in the public interest.

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