Environmental Protection Agency chief Lisa Jackson made news on two fronts in a meeting with reporters yesterday: she is preparing to officially declare carbon dioxide a pollutant under the Clean Air Act and release the final version of the Obama administration’s new fuel economy standard for autos.

EPA administrator Lisa Jackson (Photo: Legal Planet)

Neither move is necessarily unexpected. The designation of CO2 as a pollutant, often referred to as an "endangerment finding," was mandated by a two-year-old Supreme Court decision, and the higher fuel-efficiency rules were first unveiled in May.

But both could have momentous implications for environmental and transport policy. An EPA endangerment finding on CO2 could serve as a potent cudgel for lawmakers who are dragging their feet on legislating against climate change amid well-funded opposition from polluting industries.

As Grist’s David Roberts noted today, the threat of regulatory limits on carbon — as opposed to a a cap-and-trade system designed by Congress — was enough to get conservative House Democrats to the table earlier this year.

If Jackson moves now, it could give a healthy push to conservative Senate Democrats who appear to believe no climate change bill (and no possibility for extra transit investment) is a viable alternative.

The EPA’s forthcoming specifics on the fuel-economy standard, also known as CAFE, present a different challenge. German luxury-car makers could reap the benefits if the new CAFE rules include a loophole that would exempt auto companies selling fewer than 400,000 models annually in the U.S.

Should the German loophole make it into the final CAFE regulation, which would require vehicles to get an average of 35.5 miles per gallon by 2016, environmental groups as well as larger auto companies are likely to raise the alarm.

It’s looking like a momentous autumn in Washington …