'The science is undeniable': Biden and Kamala Harris promise to slash US carbon emissions in HALF by 2030 in virtual climate summit with Putin, Xi Jinping and 38 other world leaders President Joe Biden issued a call to action to world leaders, asking them to work together to combat climate change as he kicked off Climate Summit 'The signs are unmistakable. The science is undeniable. The cost of inaction is mounting,' Biden said in his opening remarks Biden vowed the US would do its part, pledging the country will cut emissions blamed for climate change by 50 to 52 percent by 2030 All 40 world leaders invited were in attendance