By Russell Gold, Ruth Bender and Peter Landers 

President Biden's move to rejoin the Paris climate accord within hours of his inauguration was welcomed by world leaders, but reasserting global leadership -- and meeting the U.S.'s commitments to reduce greenhouse-gas emissions -- promises to be challenging.

China and other nations have recently increased their pledges to do more to tackle climate change, and corporations are heavily investing in the technology needed to run the global economy with fewer greenhouse-gas emissions.

But global emissions continue to rise, and groups tracking progress question whether many of the countries that have signed the Paris agreement are currently on track to hit the targets they set to reduce their share.

Still, with China, the European Union and the U.S. all focused simultaneously on this issue, there was cautious enthusiasm that progress could be made.

"It's very clear we will only be successful globally if we have the major players on board," said Markus Beyrer, director general of BusinessEurope, an umbrella organization for EU national chambers of commerce. The U.S. return "can bring us back on track."

The Paris climate agreement is a joint effort to significantly reduce greenhouse gas emissions by 2050 in a bid to contain the rise in global temperatures to no more than 2 degrees Celsius, and preferably to no more than 1.5 degrees, to limit the impacts of climate change.

Each signatory to the pact -- signed in 2016 by the U.S. and more than 190 other countries -- set individual targets to reduce their emissions by certain dates. The U.S. entered the agreement under President Barack Obama, then exited under President Donald Trump, and is now rejoining under Mr. Biden.

Mr. Biden inherits an economy that has been reducing its emissions, albeit not fast enough to meet its commitments under the agreement. U.S. emissions have fallen in recent years as the country has retired a large portion of its coal-burning power-plant fleet, replacing it with lower-emission natural gas plants as well as renewable energy from wind and solar farms.

Last year, U.S. emissions were 21.5% below 2005 levels, according to a preliminary estimate by the energy and economics research firm Rhodium Group, not on track to meet the country's target of 26% to 28% reduction by 2025 -- and 80% by 2050.

Global emissions figures, including those of the U.S., fell sharply in 2020, mostly due to pandemic-related shutdowns of travel and economic activity. They are expected to rebound this year as the arrival of Covid-19 vaccines helps restore more-normal levels of economic activity.

The U.S. isn't alone in making progress but falling short of the longer-term objectives.

Japan is ahead of schedule to meet its near-term Paris commitment, but some environmental groups say its self-imposed target was too lenient and should be increased. The European Union under the Paris agreement is targeting by 2030 a 40% emissions cut from a 1990 level and believes it can meet its target. Last fall, it upped its target to a 55% reduction.

China is also on track to achieve the Paris Agreement goals it ratified in 2016, but these included continuing to increase its emissions through 2030. This week, China's National Energy Administration said the country had added almost 72 gigawatts of wind power in 2020 -- almost triple the amount compared with the previous year -- and 48 gigawatts of solar. Still, coal remains a major source of power generation in China, making up 57.7% of the country's energy mix in 2019, according to China's statistics bureau.

Observers say countries are struggling to meet their commitments, despite these optimistic pronouncements.

"While a turning point in global emissions seems to be within reach, five years after the Paris Agreement no country is on a path compliant with the Paris Agreement goals," concluded the Climate Change Performance Index report issued in December by Germanwatch, an independent research firm that assesses climate action in several dozen of the countries with the highest global emissions.

Under terms of the pact, the countries gather every five years to assess compliance and, if necessary, ratchet up targets. The first such meeting is scheduled to take place later this year in Glasgow. European Union officials, in welcoming the U.S. return to the Paris agreement, said the meeting would be "a crucial moment to increase global ambition."

Since the U.S. announced its intention to withdraw from the Paris accord in November 2019, several nations have stepped up their goals. The European Union increased its target to cut greenhouse-gas emissions and pledged to become completely carbon neutral by 2050. Last year, China pledged that its carbon-emissions would peak by 2030 and reach carbon neutrality by 2060.

That has raised pressure on Mr. Biden's new administration to make a similar pledge to accelerate greenhouse-gas emissions cuts and provide a policy framework to reach the goal. Such a move could inspire other nations to follow suit.

"I hope that the United States will not simply rejoin the agreement but will also be a leader for the world with strong actions," said Takeshi Niinami, chief executive of Suntory Holdings Ltd. and an adviser to Japan's Prime Minister Yoshihide Suga. "With bold commitment from this world leader, we can hope to see other countries follow suit and notably move the needle."

Rebecca Henderson, an economist and university professor at Harvard University, said the Biden administration has its work cut out.

"In order for this to be something more than simply a nice gesture, the U.S. has to begin seriously reducing its carbon emissions and putting in place the kind of policies and regulation that will ensure that progress continues," she said. Passing an infrastructure stimulus bill with a significant carbon-emission reduction component would "go a long way to increasing the U.S.'s credibility."

During the campaign for president, Mr. Biden talked about the need to make large investments in renewable energy and electric vehicles. On his first day, he took several steps to reverse Trump administration policies that loosened environmental restrictions. Mr. Biden revoked a key permit for the Keystone XL oil pipeline and ordered a review of policies that suggests he supports tougher emissions standards of power plants and increased fuel-efficiency for auto makers.

While Mr. Biden faces challenges in enacting an ambitious plan to reduce greenhouse gases, including a thin majority in Congress, the U.S. business community increasingly supports actions on climate. Last fall, the Business Roundtable said it supported the U.S.'s Paris commitment and endorsed a price on carbon emissions.

"We are pleased and proud to support the United States re-entry to the Paris Climate Agreement, and we hope that everyone shares our optimism that this is a fresh start for a common cause," said Bill Ford, executive chairman of Ford Motor Co.

--Noemie Bisserbe, Daniel Michaels and Sha Hua contributed to this article.

Write to Russell Gold at russell.gold@wsj.com, Ruth Bender at Ruth.Bender@wsj.com and Peter Landers at peter.landers@wsj.com

(END) Dow Jones Newswires

January 21, 2021 14:53 ET (19:53 GMT)