EXPLAINER: How come nations’ climate targets don’t compare?

WASHINGTON (AP) — This week’s climate change summit features lots of talk from different nations about their goals for reducing carbon emissions. But in the weird world of national climate pledges, numbers often aren’t quite what they seem. Sometimes a 55% reduction is about equal to 50% to 52%. Sometimes it’s even less. Sometimes it’s way more. That’s because as part of the Paris climate agreement process, each nation picks its own national goals for how much greenhouse gas should be cut by 2030 and — crucially — what baseline year they start counting from. That makes it difficult to compare countries’ emissions-cutting pledges to see who is promising more.