The pandemic has meant very few diplomatic trips in the early days of the Biden administration. But this week brought an exception, as White House climate envoy John F. Kerry hopped a commercial flight to meet masked face to masked face with allies in London, Brussels and Paris.

“What we’re trying to do is raise the ambition of many countries, of all countries,” the former U.S. Secretary of State said from Paris on Wednesday. “Because we’ve been absent for four years and there’s been an absence of any dialogue on climate — and these countries have all been basically dissed over these last four years — President Biden thought it was important for us to be able to conduct this essential personal diplomacy at this point in time.”

Kerry aims to demonstrate that the United States not only has rejoined the international effort to slow global warming, but also wants to lead other signatories in realizing the central aims of the 2015 Paris climate accord. Even as the Biden administration has promised to take significant steps at home, it also wants to persuade other major economies, such as China and India, to move more aggressively to cut their carbon emissions.

Kerry’s packed visit — since Monday, he has met with foreign secretaries, business and industry leaders, the head of NATO, European Union climate chief Frans Timmermans, British Prime Minister Boris Johnson and French President Emmanuel Macron, among others — carried an unmistakable sense of urgency.

In one regard, the Biden administration is racing to prepare for a high-profile gathering on April 22, Earth Day, when the White House plans to convene leaders from some of the world’s major economies, as part of a push to get the globe’s biggest polluters to commit to greater reductions. The event will be a precursor to a U.N. gathering in Scotland this fall, in which nations are expected to outline plans to begin drastically reducing emissions by the end of the decade.

In the broader sense, Kerry’s visit also underscores the urgency that Biden has repeatedly expressed about the growing risks posed by a warming climate — and the economic and environmental opportunities that lie in embracing a shift away from fossil fuels.

“One of the purposes of my coming over here, and one of the purposes of these conversations we’ve been having, is to impress on people that we view this decade as the decade of action,” Kerry said Wednesday, adding that the United States and its allies must make “a very genuine effort” to try to hit the most ambitious goal of the Paris accord — limiting the Earth’s warming to 1.5 degrees Celsius (2.7 Fahrenheit) above preindustrial levels.

Biden and Kerry have said the United States will soon unveil a far more aggressive plan to put the nation on the path toward net-zero emissions no later than 2050, and to take meaningful steps to significantly begin reducing the country’s carbon footprint by 2030. The United States is the second-biggest emitter, behind China, of carbon dioxide, the most abundant greenhouse gas.

Officials across multiple federal agencies — not to mention various environmental and scientific groups — have been busy crunching numbers to figure out the most significant promise Biden can make, and what mixture of policies would be required to achieve it.

During four years under President Donald Trump, the nation backed away from its climate commitments and became the only country in the world to withdraw from the Paris agreement. Even as Kerry tries to reposition the United States as a leading force for global climate action, European officials have so far been more aggressive in their approach to the problem.

The European Union, whose leaders met with Kerry on Tuesday, has pledged to cut net greenhouse gas emissions at least 55 percent by 2030, compared with 1990. The United Kingdom, where Kerry spent Monday with Johnson and other top officials, has promised to reduce its emissions 68 percent by the end of the decade.

Kerry’s push to rally U.S. allies and create momentum for stronger action from countries around the globe is fueled by the fact that the world remains woefully off target in the goals set out under the Paris agreement.

An analysis by the United Nations last month found that while dozens of countries, representing about 30 percent of global emissions, had submitted updated pledges ahead of a key U.N. climate summit this fall in Glasgow, they were not nearly bold enough.

Even if countries follow through, their combined impacts currently would put the world on a path to achieve only a 1 percent reduction in global emissions by 2030, compared with 2010 levels, the analysis found. By contrast, scientists have said that emissions must fall by nearly 50 percent this decade for the world to realistically have a shot at avoiding increasingly catastrophic climate impacts.

“While we acknowledge the recent political shift in momentum toward stronger climate action throughout the world, decisions to accelerate and broaden climate action everywhere must be taken now,” Patricia Espinosa, executive secretary of the U.N. Framework Convention on Climate Change, said at the time.

Kerry said he believes that remains possible and essential. He also said the tenor of his talks this week has shifted noticeably from only a few years ago.

“It is different, distinctly,” he said. “This is now a major priority in all of these nations.”

Timmermans, the E.U. official, shares the view that the world must move quickly — and move together.

“It’s going to be quite an effort to get there. It’s going to be quite an effort to convince other major players in the world to do the right thing,” he said in brief public remarks this week as Kerry looked on. “But I’m absolutely convinced that the United States and Europe, working together, we can move mountains.”