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.

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 it starts counting from for those cuts. That makes it difficult to compare countries’ emissions-cutting pledges to see who is promising more.

US AND EU GOALS

Both the United States and the European Union are offering similar-sounding pledges of cutting around half their emissions by 2030. But depending on what year you start from, each can sound significantly deeper than the other.

The European Union goal, newly approved by the union’s parliament, is 55% below 1990 levels. The new U.S. goal announced Thursday by President Joe Biden is 50% to 52% below 2005 levels.

If you convert the European goal to the American-preferred 2005 baseline, the two are the same. The European Union goal translates to 51% below 2005 levels, which is on par with the U.S. goal, said former Obama White House environmental aide Kate Larsen, a director at the private research Rhodium Group.

But if you compare them using Europe's preferred 1990 as the baseline, the 50% minimum U.S. cut is only 41%, far shy of the 55% EU goal, according to Larsen’s calculations.

If you compare the numbers to 2019, the last pre-pandemic year, the U.S. goal looks more ambitious than Europe's. The minimum the United States would be cutting is about 40% from today’s level and the EU...