America is back at mid-1990s levels of carbon dioxide emissions. Some of that is due to the ongoing recession, of course, but a large chunk is due to the switch from the dirty coal plants that ballooned after America stopped producing emissions-free nuclear energy to natural gas.
While energy overall is back at early 1990s levels of emissions, coal specifically is back at early 1980s levels of emissions.
And it's all been done without mitigation, rationing or increased cost, even during a political climate of hostility against traditional energy. It isn't just CO2; "combined cycle" natural gas power plants also release significantly less nitrogen oxides and sulfur dioxide, finds a study
in Earth's Future.