President Trump made the announcement Thursday- saying the United States will be pulling out of the Paris climate accord because he feels it hurts the USA while giving other countries an economic edge.
With Trump's action, the United States will walk away from almost every nation in the world on one of the pressing global issues of the 21st century.
But America can't pull out of the accord immediately.
"If we don't do anything, we might shoot over 5 degrees or more and that would be catastrophic", said John Reilly, the co-director of the program, adding that MIT's scientists had had no contact with the White House and were not offered a chance to explain their work.
"Tonight the United States has turned its back on the world, but France will not turn its back on Americans", he said.
China overtook the United States as the world's biggest emitter of greenhouse gases in 2007 but analysts see the USA withdrawal as an opportunity for China to burnish its image as a global leader.
"Today's decision to withdraw from the Paris Agreement underscores how important it is for major USA cities to lead the way and take definite action to leave a better planet than the one we inherited", Faulconer said.
"As the Mayor of Pittsburgh, I can assure you that we will follow the guidelines of the Paris Agreement for our people, our economy & future", Democrat Bill Peduto tweeted in a swift, widely read retort to Trump's move.More news: Man dies after ignoring new tattoos warnings
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In a commentary published on Friday, Xinhua suggested that no one country was now likely take up leadership of global efforts to fight climate change. "This decision must not stand", he said.
"As of today, the USA will cease all implementation of the non-binding Paris accord and the draconian financial and economic burdens the agreement imposes on the United States".
In a speech during the EU-China Business Summit, Jean-Claude Juncker said the parties agreed that worldwide solutions were needed in everything from the fight against terror to supporting global economic growth.
Congresswoman Tulsi Gabbard, described it as a irresponsible and short-sighted decision.
"This decision can not and will not stop those of us who feel obligated to protect our Earth", she said.
"Climate change is a threat to our country", Democratic National Committee Chairman Tom Perez, who attended the protest, said at the rally.