Earth Day and the environmental movement While more ambitious climate targets are "very encouraging indeed," said Prakash Kashwan, a professor of political science who researches climate justice at the University of Connecticut. Big emitters like the US and EU should explicitly recognize the carbon debt they owe the rest of the world instead of using their domestic actions to cajole other countries. "Lead from the front by delivering actual emission reductions." Climate ambition The 40 world leaders who met virtually for Biden's two-day summit are responsible for 80% of the yearly greenhouse gas emissions that are heating the planet and wreaking havoc in the form of worse droughts, cyclones, floods, heatwaves and wildfires.