Fifty years from now, if our children and grandchildren aren't baking on a normal 100-degree day, if coastlines aren't pushed back by a quarter mile, if you can still grow corn and beans in Missouri and wheat in Kansas, if we've developed a working relationship with a hotter planet, then Aug. 3 might be declared a national holiday.

This is not so much about what happened Monday: President Barack Obama released the final version of his Clean Power Plan. By itself, that's a big deal, but not holiday-big. It addresses the source of 31 percent of U.S. greenhouse gases, but overall would reduce America's greenhouse gas emissions by roughly 6 percent.

The bigger deal will come if it can change the conversation, if the nation overcomes political opposition to it and buys in to addressing climate change. The biggest deal would come in Paris in December, at the 21st U.N. Climate Conference in Paris.

If the rest of the world, following belated U.S. leadership, seizes its last-ditch opportunity to seriously address the worst effects of climate change, then Aug. 3 will be as good a day as any to celebrate.

Climate change is really not negotiable. It's not a states' rights issue. This is a slow-moving catastrophe that, to one extent or another, threatens all forms of life on the planet. You can deny it. You can say there are too many "ifs," but the climate doesn't care. The sixth extinction has begun and it's moving faster.

This generation either slows things down to sustainable rates or future generations suffer a global cataclysm that will make World War II look like a bad thunderstorm. The only comfort is that we'll be gone by then, which seems to be enough for many people.

What happened Monday was that the Environmental Protection Agency finalized regulations first released as draft proposals in 2012 and 2014. They're aimed at shutting down hundreds of older, coal-fired power plants, stopping construction of new ones and replacing their generating capacity with gas-fired plants, renewable energy sources and possibly next-generation nuclear technology.

The final regulations set a 15-year goal of reducing greenhouse gas emissions from power plants 32 percent from the 2005 baseline. That's a slightly more stringent target than the 30 percent called for in the draft regulations, but then we're already almost halfway to the goal. Power plant emissions already dropped 15 percent between 2005 and 2013. It took a recession, cheap shale gas and steady growth in renewable sources and energy efficiency.

Another 20 percent in 15 years is doable. Each state will get its own target and each will be able to tailor its own plan — or have the EPA do it for them.

Meeting greenhouse gas standards is not free, nor should it be. Everything has a cost. The issue is allocating it fairly.

But the cost shouldn't be exorbitant, either. A study done at Georgia Tech found that some states will see electric bills go down as utilities move to gas and renewables and aggressively pursue energy efficiencies. Utilities can get greenhouse gas reduction credits without constructing expensive new gas-fired generation stations.

Ashok Gupta, a senior energy economist at the Natural Resources Defense Council, has been studying Ameren's possible responses to the Clean Power Plan. "If Ameren can move from coal to renewables without first building a gas plant, it can take advantage of a lot of carbon credits under the plan," he said. "If Ameren wants to do efficiencies or solar in low-income communities, it can get credits."

The earlier that utilities pursue such strategies, the more credits they get. "It's good for their shareholders and less risky to follow the plan rather than build big new plants," Mr. Gupta said.

There are amazing gains to be made in energy efficiencies. "In a city like St. Louis, some 3 to 5 percent of buildings use half of the energy used by all buildings," he said. "They are government, universities, hospitals, apartments and office buildings."

Identify those buildings, fix them and you're well on your way to your goal.

In short, this doesn't have to be the economic doomsday scenario portrayed by congressional Republicans who have vowed to try to block the Clean Power Plan. Modest, affordable steps can make a difference. New jobs can be created in renewable energy fields.

Or we can pander and stall, and present the grandchildren with a real doomsday scenario.

REPRINTED FROM THE ST. LOUIS POST-DISPATCH