Even for people who don’t believe in it, climate change just got real. It’s about time.

The Obama administration’s proposed new rule for existing power plants — reducing heat-trapping carbon emissions by up to 30 percent by 2030 — is ambitious enough to get anyone’s attention. No, this one measure will not halt or reverse human-induced warming of the atmosphere. But the rule is necessary in the context of seeking international consensus on solutions — and also significant in its own right.

Before Environmental Protection Agency Administrator Gina McCarthy could announce the new rule Monday, critics were already bellowing about higher energy rates and lost jobs. They pretended not to see that President Obama — as with health-care reform — is taking what ought to be seen as a Republican-friendly approach.

The rule, which will not become final until next year, gives states great flexibility in how they reach the target. They are not forced to immediately begin shutting down the aging coal-fired power plants that constitute one of the biggest sources of carbon pollution. Rather, each state can take the path that best fits its circumstances — ramping up the generation of energy from renewable sources such as wind and solar, for example, or entering regional cap-and-trade agreements.

Ultimately, however, hundreds of those aging, dirty, coal-fired plants will have to close. If the planet could speak, it would say good riddance.

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Many of those who do not believe in climate change also reject the idea that carbon dioxide can be called a pollutant, since it is a natural and necessary component of the air we breathe. But direct measurement shows that the concentration of carbon dioxide in atmosphere has increased by an astounding 40 percent since the beginning of the Industrial Revolution, when humankind began burning fossil fuels in earnest. As with any poison — or pollutant — it’s the dose that counts.

This thickening pall of human-generated carbon dioxide — which traps heat, according to universally accepted principles of physics and chemistry — has coincided with a long-term rise in average temperatures that agrees with climate scientists’ predictions. The big unanswered question isn’t scientific, it’s political: Will we continue to turn up the thermostat?

The question that some skeptics like to pose — “Why should the United States take such a big step on its own?” — is meaningless when you think about it.

China is the world’s largest emitter of carbon dioxide. Emissions are rising sharply in India and other rapidly industrializing countries. Nothing the United States does unilaterally, or even in concert with Europe and Japan, can solve the problem. What we really need is a global solution.

All this is true, but one less ton of carbon makes a difference, however slight. Obama’s major energy initiatives — higher fuel economy standards for vehicles, plus the new power plant emissions rule — will mean billions of tons less of carbon dioxide in the air. It is true that we cannot save the planet on our own. But it is also true that if warming-induced disaster is inevitable, it will arrive sooner if we fail to act.

Meanwhile, Chinese and Indian universities are full of scientists who are warning their own governments about the negative impacts of carbon emissions. China has already signaled its intention to move away from coal, and while this is easier said than done, Chinese officials have an added incentive: The noxious smog that shrouds major cities, most of it from coal-fired power plants, has stoked real anger among the country’s burgeoning urban middle class. In other industrializing countries as well, as people get richer they will demand a cleaner environment.

Obama hopes that action by the United States, the richest country in the world, will make it possible for the other big carbon emitters to act. Some of the domestic critics who scoff at this notion also complain that Obama, in their view, does not sufficiently assert U.S. leadership around the globe. What do these people think leadership means, if not actually leading?

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The bonus is that closing coal-fired power plants will encourage the development of cleaner energy sources. The power generation industry was already moving toward cheap, plentiful natural gas, which releases much less carbon. Gas should be seen as a bridge toward clean, renewable energy sources — an industry that will be huge in the 21st century.

It’s our choice. We can try our best to ensure that the next Industrial Revolution — the one that ends dependence on fossil fuels — happens here. Or we can watch it happen in China.

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