The U.S. is seeking to reduce the greenhouse gases it produces by at least half by 2030, as President Joe Biden carries out his decision to rejoin the Paris Agreement. America’s new commitment -- officially known as a nationally determined contribution, or NDC -- is much more ambitious than its initial one. It will need to be. Climate change hasn’t slowed enough since the landmark international pact was signed in 2015, and several other nations that have already increased their own objectives.

1. What’s an NDC?

NDCs are the heart of the Paris Agreement among almost 200 countries to reduce the fossil fuel pollution that causes climate change. They’re voluntary targets that each nation sets for themselves, committing to cut greenhouse gas emissions by a specific amount. They vary from country to country and are generally based on multiple factors, including how much of those heat-trapping gases a country generates, what kind of changes people and businesses there are willing to make, and what it would take politically to make that happen.

2. What was the initial U.S. goal?

When the agreement was signed, President Barack Obama pledged to reduce U.S. emissions 26% to 28% below 2005 levels, by 2025. Even then, scientists said the initial NDCs set by the signatories collectively weren’t aggressive enough to keep global warming well below 2 degrees Celsius, the limit researchers thought at the time was necessary to avoid the most catastrophic affects of climate change. That’s why the pact includes a schedule for signatories to periodically increase their NDCs.

3. What is the U.S. doing now?

The U.S. is now pledging to reduce greenhouse gas emissions by 50% to 52% by 2030; climate advocates and environmental groups had been calling for a target of at least 50%. That would help put the world on track to limit warming to no more than 1.5 degrees above pre-industrial levels, the more ambitious target that researchers now say is needed to avert climate disaster.

4. Is that feasible?

Maybe. Former President Donald Trump pulled the U.S. out of the Paris Agreement and implemented federal policies friendly to fossil fuels. But cities, states and corporations picked up a lot of the slack with aggressive efforts to embrace clean energy and curb emissions. As a result, the U.S. isn’t too far off pace to meet its initial NDC goals. Ramping up to meet a bigger target in 10 years will be a challenge, though. Biden has announced plans to put a lot of money into boosting renewable sources of energy and use of electric vehicles, but he’ll face resistance from Congress, as well as oil companies and other industries that are threatened by the green transition.

5. What are the penalties for countries that don’t meet their goals?

There aren’t any. NDC targets are strictly voluntary. But there’s a lot of international peer pressure for countries to meet the targets they’ve set for themselves and also to increase them. The real penalties are already being felt as the changing climate leads to record hurricane seasons, drought, wildfires and more extreme weather.

6. What have other countries pledged?

The U.K. said in April it will cut carbon pollution by 78% by 2035. The European Union in December increased its NDC target to 55% below 1990 levels by 2030 and pledged to completely eliminate carbon emissions by 2050. Dozens of other nations including the U.K., Japan, South Korea and Canada have made similar commitments. China, the word’s biggest source off greenhouse gases, has said it’s aiming for net-zero emissions by 2060. The Paris Agreement called for nations to “ratchet up” their NDCs after five years. That first big test was supposed to occur at the annual UN climate conference last year in Glasgow, but the event had to be delayed because of the global pandemic.

7. What happens next?

The Glasgow conference, known as COP 26 and expected to start in November, is going to be a big deal. There are a lot of expectations for countries to show up with new, more ambitious NDCs. John Kerry, the U.S. special presidential envoy for climate, has been criss-crossing the globe to encourage world leaders to move quickly and aggressively on curbing emissions. And many of those leaders are watching to see if the U.S. follows its own advice with a big NDC target.

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