We all make choices, and some turn out better than others do. But the choices we end up regretting the most are usually the ones we make against our better judgment. Both individually and collectively, we humans seem uniquely capable of acting as our own worst enemy.

We also are capable of wonderful, positive, and inspiring actions. That makes it all the worse when the consequences of a single bad decision overshadow our best intentions. And that, I'm afraid, is what the Obama administration risks by recklessly expanding fossil fuel production on public lands.

The Climate Action Plan that President Obama announced last year is full of good ideas, and his administration has already done more to address carbon pollution than any other has. New fuel-economy standards will double the efficiency of our cars and trucks. The energy efficiency of our appliances and buildings will dramatically improve. Stimulus spending has helped boost clean, renewable energy, and the president has directed the Environmental Protection Agency to set standards to curb both toxic emissions and carbon pollution from coal plants.

Unfortunately, a hard look at the numbers shows that all this progress could be undermined by one bad choice -- expanding fossil fuel production. Using publicly available data already gathered by federal agencies, the Sierra Club has calculated the potential carbon dioxide emissions from dirty-fuel development proposals in a new report, Dirty Fuels, Clean Futures. Such calculations send a clear message: To protect our climate, we must keep these dirty fuels in the ground.

Extracting and burning these coal, oil, gas, oil shale, and tar sands resources would release hundreds of billions of tons of carbon into the atmosphere and negate carbon-reducing actions. If we develop just one of these "climate disrupters" -- the Arctic Ocean, for example -- we'll release two-and-a-half times more pollution than we are saving through stronger fuel-economy standards.

Of course, that carbon pollution would be in addition to the already high toll from destructive mining, drilling, and fracking: polluted drinking water, destroyed wildlife habitat, and air that is dangerous to breathe. No matter where it happens, dirty fuel development leaves a trail of destruction. Throughout Dirty Fuels, Clean Futures, you'll find profiles of activist heroes around the country who are working to stop that destruction.

The world's best climate scientists have made it clear: To have even a two-thirds chance of keeping global temperature rise to less than 3.6 degrees Fahrenheit, we cannot exceed more than 469 billion additional tons of carbon dioxide pollution, yet burning existing worldwide reserves oil, gas, and coal would release 2.8 trillion tons of new carbon dioxide. That's why the Obama administration (and future leaders) will need to complement policies that reduce fossil-fuel consumption (and promote clean energy) with similar measures that limit dirty fuel extraction on U.S. public lands. It would be a mistake to see that as self-denial. In fact, committing to a future powered by clean, renewable energy will mean a healthier America with cleaner air and water, pristine coasts, and protected natural areas. As fossil fuels leave the picture, ours will be a wealthier, more just, and more productive nation.

For all these reasons, we urge that President Obama reject these dirty fossil-fuel projects and choose instead to maintain our national momentum toward a 100 percent clean energy future. The data in Dirty Fuels, Clean Futures leaves no excuse for saying we didn't know better.