washington—president joe biden said that the united states is facing “a climate in crisis” among other challenges in his inauguration speech wednesday, marking the beginning of a presidency that promises to take unprecedented action on the global emergency.

“we face an attack on our democracy and on truth. a raging virus, growing inequity, the sting of systemic racism, a climate in crisis, america’s role in the world,” biden said. “any one of these would be enough to challenge us in profound ways. but the fact is, we face them all at once.”

many environmental activists were relieved to hear biden reinforce his commitment to addressing the climate crisis after former president donald trump consistently played down the threat of climate change over the past four years.

“what a difference a day makes,” said john noël, a senior climate campaigner with greenpeace usa. “we are at a complete 180 from the trump administration that stressed a borderline criminal approach to climate action and total deference to the fossil fuel industry.”

biden backed up his rhetoric almost immediately, signing an executive order to return the u.s. to the paris climate agreement and renew its international commitment to reduce carbon emissions in the near future as one of first actions in office. biden also signed executive orders halting the keystone xl pipeline from canada to texas and putting a temporary moratorium on oil and gas leasing activities in the arctic national wildlife refuge, both of which were intensely opposed from environmentalists.

he also asked the department of interior to review the deteriorating conditions of the grand staircase-escalante, northeast east canyons, bears ears, and seamounts marine national monuments.

natalie mebane, associate director of united states policy at 350 action, an environmental advocacy political action committee, said she was very pleased with biden’s decisions to rejoin the paris climate agreement and halt the keystone xl pipeline. “i’ve been fighting keystone since it was proposed back in 2008,” mebane said.

however, the executive order to block the pipeline seemed to irritate sen. john barrasso, r-wyo., a potential forewarning of the backlash biden’s ambitious climate agenda may create among congressional republicans.

“my concern is, of course, some of the executive orders that are coming, specifically in regard to the keystone xl pipeline – it was a speech of unity and it’s important to govern that way as well,” barrasso said, referring to biden’s calls for unity in his inauguration speech.

the new president may also face opposition from progressive democrats and activists who want to see much more dramatic action and policy on reducing carbon emissions.

“rejoining the paris agreement is great, but that’s not the end of the story. a lot of work needs to happen to establish a new identity and then live up to it. revisiting pipeline decisions is fine, but we still have to decarbonize,” said daniel bresette, executive director of environmental and energy study institute.

biden will now embark on an unprecedented climate agenda to make progress on an issue that the president sees as the greatest challenge the country and world faces. his plan includes an investment of $2 trillion in renewable energy and overhauls of transport and manufacturing in the hopes of reaching net-zero emissions by 2050.