The 2015 Paris climate agreement represents one of the first attempts at a truly global response to the threat of climate change. For nearly two years, the pact has linked almost every country in the joint effort to cut back greenhouse gas emissions and stave off human-influenced climate change. As of yesterday, that effort does not include the United States.

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President Donald Trump announced on Thursday that the U.S.—a major player on the climate scene and one of the treaty's de facto leaders—would be pulling out of the historic pact. “In order to fulfill my solemn duty to protect America and its citizens, the United States will withdraw from the Paris Climate Accord,” he announced at a press conference at the White House Rose Garden.

The controversial decision makes the U.S. one of just three countries that are not part of the voluntary agreement, the other two being Syria and Nicaragua. It also reverses the past administration’s efforts on climate change, following recent actions to begin dismantling Obama-era climate protection policies.

But it doesn't take America out of the climate equation. No matter how you crunch the numbers, the U.S. still ranks among the top greenhouse gas emitters in the world. Based on data from the European Commission, Joint Research Center/Netherlands Environmental Agency and Emissions Database for Global Atmospheric Research, the top five emitters in what’s known as "carbon dioxide equivalents" (CO2 eq) released in 2012 are as follows:

China (12.45 million kilotons CO2 eq) United States (6.34 million kilotons CO2 eq) India (3.00 million kilotons CO2 eq) Brazil (2.99 million kilotons CO2 eq) Russian Federation (2.80 million kilotons CO2 eq)

Importantly, these numbers are based on CO2 equivalents. That means they include all the greenhouse gases a country emits—including carbon dioxide, methane, nitrous oxide and fluorinated compounds—to reflect the fact that warming results from a combination of gases released from both natural and human activities. By measuring emissions in equivalents, scientists can take into account the differing impacts of each of these gases on the atmosphere.

You’re probably familiar with carbon dioxide, which is emitted through fossil fuel combustion and industrial processes, as well as forestry and land use. It’s by far the most ubiquitous gas humans emit, composing 76 percent of global greenhouse gas emissions in 2010. But methane comes in at an important second. A much more potent warming agent, scientists estimate that methane has 25 times greater impact than CO2 over a 100-year period. And while it isn’t just cow farts driving this trend, agricultural activities—including waste management—and burning of biomass do release methane into the environment.

Under the Obama administration, the U.S. had committed to a 26 to 29 percent reduction of greenhouse gas emissions below its 2005 level by 2025. However, as an analysis from four European research organizations known as the Climate Action Tracker points out, without any further action, the country will miss its commitment “by a large margin.” One of the most significant steps in U.S. climate actions was the Clean Power Plan, announced in August 2015. But the EPA has been ordered to review and possibly revise this plan, which mean significant challenges lay ahead in meeting emissions targets.

Overall, global CO2 emissions have slowed since 2012, which could reflect changes in the world’s economy and investments in energy efficiency. Both China and India—the two other leading greenhouse gas emitters—are well on track to meeting their emission goals, according to the Climate Action Tracker. China in particular has taken significant steps toward shuttering coal-fired power plants and increasing its reliance on renewable energy. Experts predict that America’s withdrawal from the Paris agreement gives the Chinese government the opportunity to take the lead in the fight against climate change.

What will the actual effects of America’s withdrawal look like? For starters, nothing will happen immediately. The accord stipulates a four-year legal process for a country to pull out, meaning the soonest the U.S. could officially withdraw is 2020 (as news outlets have pointed out, this also means that a future U.S. president could potentially opt to stay in).

Even then, many argue that the move won’t necessarily change U.S. progress toward reducing its emissions. From falling renewable energy prices to state-level commitments to continue efforts to staunch emissions, America is already working toward lowering greenhouse gasses. Others have argued that the Paris Agreement could even be stronger without U.S. participation, which—with President Trump’s stated commitment to bringing back coal and reduce regulations on industry's emissions—could “water down” the treaty’s goals, writes Robinson Meyer for The Atlantic.

Moreover, as a recent Gallup poll suggests, the American public strongly supports a continued shift away from environmentally harmful forms of energy like oil, gas and coal, with 71 percent favoring an emphasis on alternative energy sources like solar and wind. “Given the choice, the majority of Americans think protecting the environment should take precedence over developing more energy supplies, even at the risk of limiting the amount of traditional supplies the U.S. produces,” according to Gallup’s website.

It is now up to the American public—as individuals, companies and communities—to take the lead in reducing their impact on the environment in whatever way they can. As David Moore, ecosystems scientist at the University of Arizona wrote on Twitter after the announcement: “Walk it off … walk it off … then get to work with your local school, city, or state to make the world more sustainable.”