When President Donald Trump announced that the United States was withdrawing from the Paris climate agreement, he justified the move by saying "the bottom line is that the Paris accord is very unfair, at the highest level, to the United States." Is it?
To assess Trump's claim, it is important to understand that when we ask how much countries should cut their greenhouse gas emissions, we are essentially discussing how to distribute a limited resource. It's as if we were discussing how to divide an apple pie when more hungry people want a big slice than there are big slices.
In the case of climate change, the pie is the atmosphere's capacity to absorb our emissions without triggering catastrophic change to our planet's climate. The people wanting big slices are the countries that would like to emit large quantities of greenhouse gases.