It may only be his first full day in office, but President Joe Biden has wasted no time in undoing many policies from the previous administration. 

One such move was to rejoin the Paris Climate Agreement, a legally-binding accord created in 2015 that commits member countries to put forward plans for reducing their emissions of greenhouse gases such as carbon dioxide, which is released from burning fossil fuels. The United States was among the 196 countries that adopted the agreement in Dec. 2015. 

But former President Donald Trump had questioned the scientific warnings about man-made global warming, at times accusing other countries of using the Paris accord as a club to hurt Washington. The U.S. formally left the pact on Nov. 4, the day after the 2020 presidential elections. 

Biden, who made addressing climate change one of his leading campaign issues, had long promised to rejoin the accord should he win the presidency. 

"I, Joseph R. Biden Jr., President of the United States of America, having seen and considered the Paris Agreement, done at Paris on December 12, 2015, do hereby accept the said Agreement and every article and clause thereof on behalf of the United States of America,” Biden’s official proclamation read Wednesday. 

Soon after, world leaders applauded Biden as he kept his word and rejoined the global effort to curb climate change. 

British Prime Minister Boris Johnson praised Biden’s decision as “hugely positive news” on Twitter, saying he looks “forward to working with our US partners to do all we can to safeguard our planet” at the UN Climate Change Conference in Glasgow later this year. 

French President Emmanuel Macron similarly welcomed the United States back to the climate accord on Twitter, saying the Biden-Harris inauguration marked a “most significant day for the American people.” 

“We are together,” Macron continued. “We will be stronger to face the challenges of our time. Stronger to build our future. Stronger to protect our planet.”

Italy’s Prime Minister Giuseppe Conte, who is also the current G20 president, called Biden’s announcement “fantastic news.”

“Italy looks forward to working with the US to build a sustainable planet and ensure a better future for the next generations,” Conte added.

German Chancellor Angela Merkel was more muted in her reaction, noting merely that her government would "probably have a more similar opinion" with Biden on issues such as the Paris climate accord, migration and the World Health Organization.

Germany’s Environment Minister Svenja Schulze, of the center-left Social Democrats, voiced greater excitement at Biden’s move. “The U.S. is rejoining the fight against the climate crisis with great verve and enthusiasm,” Schulze said, adding that she hoped the new U.S. administration would use the upcoming global summit to “reinforce their pursuit of climate neutrality with a concrete intermediate target for 2030.”

Canadian Prime Minister Justin Trudeau, who on Wednesday said he is “disappointed” in President Joe Biden’s decision not to move forward with the Keystone XL Pipeline, nonetheless commended the president’s decision to rejoin the Paris accord. 

Trudeau said he raised Keystone XL as a top priority when he spoke with Biden in a phone call in November. The project would have expanded critical oil exports for Canada, which has the third-largest oil reserves in the world.

“Despite President Biden's decision on the [Keystone XL Pipeline], we would like to welcome other executive orders made today, including the decisions to rejoin the Paris Agreement and the World Health Organization, to place a temporary moratorium on all oil and natural gas leasing activities in the Arctic National Wildlife Refuge, and to reverse the travel ban on several Muslim-majority countries,” Trudeau wrote in a statement. “I look forward to working with President Biden to reduce pollution, combat climate change, fight COVID-19, create middle class jobs, and build back better by supporting a sustainable economic recovery for everyone.”

But Biden’s decision was panned by several conservative lawmakers in the United States, some of whom – like Texas Sen. Ted Cruz – accused the president of putting foreign needs above those of his constituents. 

"By rejoining the Paris Climate Agreement, President Biden indicates he’s more interested in the views of the citizens of Paris than in the jobs of the citizens of Pittsburgh,"Cruz wrote in a statement. "This agreement will do little to affect the climate and will harm the livelihoods of Americans."

Sen. Marsha Blackburn of Tennessee echoed Cruz’s concerns, tweeting Biden’s decision "will cost American jobs and force households and small business to pay higher utility bills."

But the criticism is unlikely to dissuade Biden from his ambitious agenda to address climate change. 

The president has appointed a large team to tackle climate change both on the domestic and international front. Former Secretary of State John Kerry, named as the president’s special climate envoy, on Thursday took part in a virtual event with Italian industry at which he touted the ‘green economy’ as an engine for jobs and said the U.S. planned to make up for time lost over the past four years.

Organizers of a meeting Monday on adapting to climate change said they hoped Kerry would take part too, and Biden himself has talked about inviting world leaders to a summit on the issue within his first 100 days in office.

The Associated Press contributed to this report.