After four years of near-silence about climate change in the White House, 2021 brought an abrupt shift. President Biden turned it into one of the defining issues of his presidency, proposing ambitious efforts to replace fossil fuels with clean energy sources and lead a global campaign to cut greenhouse gases.

But as the year ended, it appeared that the most significant of those proposals had crashed into a wall of opposition from Republicans in Congress and one notable Democrat — Sen. Joe Manchin of West Virginia. And at a global summit, efforts to fight climate change lagged well behind promises to do so.

On Biden's first day in office, he announced that the United States was rejoining the 2015 Paris Climate Agreement, in which nearly 200 countries agreed to drastic cuts in their collective greenhouse emissions. A few months later, the Biden administration released a plan to rein in the country's net greenhouse gas emissions, across the economy, by at least 50% by 2030 and to zero by the middle of this century.

Throughout the year, Biden called climate change a crisis. "This is a moral imperative, an economic imperative, a moment of peril, but also a moment of extraordinary possibilities. Time is short, but I believe we can do this," he said, during a climate conference with other countries in April.

When Biden or a member of his administration talked about climate change, they almost always focused on the jobs that could be created through this transition to cleaner forms of energy. It could also mean many jobs lost in the fossil fuel industry. But in pursuing legislation, job creation was a constant focus.

Biden tried to give his climate plan the force of law

The most important parts of Biden's climate plan found their way into two massive pieces of legislation. Congress passed one of them, a $1 trillion infrastructure package that some Republicans also supported. It included $7.5 billion to build electric vehicle charging stations as well as money to expand long-distance transmission on the electric grid, key to getting renewable energy from where it's generated to cities where it's used.

The bulk of Biden's climate agenda, however, was in a larger spending bill that has stalled in Congress. A centerpiece of that plan was a "Clean Electricity Performance Program," which would have paid utilities to transition to renewable and nuclear energy and penalized those that didn't make the transition quickly enough. The coal industry would have been the big loser under that program. Manchin, who owns a coal business, publicly rejected the plan in mid-October, and it was swiftly dropped from the bill.

Two months later, Manchin announced his firm opposition to the entire stripped-down bill. He justified his position with several false claims about climate change, including the idea that a speedy transition to renewable energy could lead to blackouts, such as those experienced in Texas and California. Those problems were mainly due to failures by power companies to prepare for extreme weather events.

Domestic roadblocks complicate U.S. climate diplomacy

The Biden administration's failure to get its most ambitious climate proposals through Congress also undermined its efforts to provide global leadership at a landmark United Nations' climate summit in Glasgow, Scotland, in November.

That summit did stimulate a round of new emissions-cutting pledges from some countries, the biggest coming from the U.S. In addition, China and India released new goals that didn't appear impressive at first glance — they pledged to get to zero emissions in 2060 and 2070, respectively — but those goals still represent a substantial change for both countries, which rely heavily on coal.

Groups of nations pledged to cut emissions of methane, a powerful greenhouse gas, by 30% over the next decade, and to end deforestation. Rich nations also promised to deliver more money to developing nations to help them adapt to climate change and to build clean energy systems, although those promises didn't come close to satisfying demands from less wealthy countries.

Yet all those promises still fell well short of what's required to meet a key goal of the Paris Agreement: to cut greenhouse gas emissions enough to limit global warming to less than 2 degrees Celsius (3.6 degrees Fahrenheit) and ideally to 1.5 degrees C (2.7 degrees Fahrenheit), compared with pre-industrial times. The conference agreed to require countries to come back in 2022 with more ambitious plans to cut emissions.

The Biden administration's experience, however, suggests that setting goals is easier than reaching them. There's political opposition to shifting away from fossil fuels in many countries, not just in the U.S.

What's next for the American climate agenda

With Congress blocking this new legislation, the Biden administration is looking for other ways to meet its emission reduction goals. This could include new climate-focused executive orders and rules from the White House. On Monday, it announced that it would raise mileage standards for new cars – an important step given that transportation is now the largest source of greenhouse gas emissions in the U.S.

Those steps face an uncertain future, though, since conservative justices on the Supreme Court have been skeptical of efforts by the White House to extend its authority under existing laws.

Despite the obstacles that the Biden administration has hit, it did succeed in dramatically shifting the national debate over climate change during 2021. Policies are now in place, or under serious discussion, that weren't even on the table in recent years. And billions of dollars are starting to flow toward infrastructure projects that are aimed at fundamentally changing the way the country generates and uses power.