Last year, humanity's output of carbon dioxide rose by 3 percent, reaching a rate of 2.4 million pounds per second. There is an angle to this datum to annoy just about everyone.

Suppose you're a conservative who doesn't believe in all that global-warmist malarkey. You've read about Climategate scientists trying to "hide the decline," you don't trust computer models and you think Michael Mann's "hockey stick" is a fraud. You're not convinced the planet is warming, doubt people have anything to do with it, and frankly don't care much if they do.

So, OK. For argument's sake, let's take global warming off the table. You still should care about CO2 emissions for another reason: ocean acidification. The oceans absorb a quarter to a third of the carbon dioxide humans release into the atmosphere, because carbon dioxide is soluble in water (hence, carbonated beverages). The CO2 reacts with seawater to form carbonic acid. The more carbon dioxide in the air, the more acidic the oceans.

The oceans are now roughly 30 percent more acidic than in the pre-industrial era. And unlike future climate change, the effects are already apparent. Just head down to the Tidewater area of Virginia or out to coastal Oregon and talk to the folks who raise shellfish.

Four years ago the Whiskey Creek Shellfish Hatchery in Tillamook, Ore., lost millions of oyster larvae. The company found the problem was, yep, the overly acidic ocean water it was pumping in. Now it treats the water when the pH balance falls too far. "For us, the only thing that is correlated with mortality is the CO2 level," said owner Sue Cudd. She was talking to the magazine Seafood Business, not some Soros-funded outfit cranking out leftist agitprop. If current trends continue, by century's end the oceans could be twice as acidic as they are now. Ocean acidification matters, says Shallin Busch of the National Oceanic and Atmospheric Administration, because of "the fish we eat and the things we make money off of."

Before we all put on the sackcloth and ashes, though, note some good news: America's carbon-dioxide emissions are actually falling. In fact, they have not been this low since 1992. And while no single factor can account for the entire shift, much of the credit goes to something environmentalists often detest: hydraulic fracturing, or fracking.

Among power sources, the worst source of CO2 emissions by far is coal. Natural gas generates half the CO2 per kilowatt-hour, and in the past few years natural gas has displaced coal to a remarkable degree. This year gas-fired electricity generation equaled coal-fired generation for the first time. According to the Energy Information Administration, that trend will continue as shale gas production rises from 5 trillion cubic feet in 2010 to more than 13 trillion cubic feet in 2035. Fracking made this possible—by opening up the Marcellus shale deposit in Pennsylvania and many others. Twelve years ago, shale gas made up 2 percent of the U.S. supply. It now makes up 37 percent.

All of that was achieved without government direction—and in the face of considerable environmental resistance. Now the world's worst CO2 emitter, China—which gets 80 percent of its electricity from coal—has taken up fracking too. China's natural-gas reserves are 50 percent bigger than America's. If climate change is the worst danger facing the planet, as some environmentalists contend, then Chinese fracking should be good news.

But most environmentalists hate fracking. Instead, they have placed their bets on other horses—many of which have come up lame (see: Solyndra, Evergreen Solar, A123 Systems, et al.). And even green-energy pursuits insulated from market forces pack a remarkably weak punch. The Navy has just built a 10-acre solar-panel field at its Norfolk Naval Station, at a cost of $21 million in Obama stimulus money. It can power all of 200 homes—a mere 2 percent of the naval station's power needs. An audit says the money saved on utility bills will recoup the project's costs in roughly 447 years (not a typo).

This is part of a bigger pattern going back decades, in which environmentalists and politicians have backed loser after loser—from the Synthetic Fuels Corporation of the 1970s to the Partnership for a New Generation of Vehicles in the 1990s. That record of failure flows from two misapprehensions: (1) the belief that government central planners can simply legislate scientific progress, and (2) the suspicion that ostensibly soulless and rapacious energy companies would rather leave huge profits on the table than explore an unfamiliar energy source simply because it might be good for the Earth.

Meanwhile, the unplanned disruptive innovation of fracking has done what all those flops could not: reverse America's CO2 emission trends. It one day might reverse the world's. That story should increase another natural resource that is in woefully scarce supply in certain circles: humility.