the sad thing is

While we're debating global warming, it's already too late... the CO2 we've already admitted will remain in the atmosphere for decades (at least), and our overall emissions are not dropping yet, therefore we are going to continue adding to the cumulative amount of CO2 in the atmosphere for a long while after we notice the effects of global warming. Once you start seeing the effects, it is already bordering on being too late to do anything about the situation.