By Robert Redford.

Obama has expressed worry about climate change, but he needs plan to address it.

Like a lot of people, I felt reassured earlier this year when President Obama spoke of the need to combat climate change for the sake of our children.

The president demonstrated leadership that night in that State of the Union address by making it clear that he doesn’t see extreme heat waves, powerful storms like Hurricane Sandy, the most severe drought in decades and the worst wildfires ever in some states as just weird coincidences.

He demonstrated leadership by calling out Congress, saying if it doesn’t act soon, he will take executive action to reduce pollution, prepare communities to cope with climate change impacts and spur us toward cleaner energy.

Clearly, the president understands the climate issue. But he owes more to future generations than his intellectual acknowledgement about the hardships they will face if nothing is done to address it. He owes them action.

I just hope the president has the courage of his convictions.

It’s what separates presidents that we don’t often remember from those we do. Years ago, an ally advised newly sworn-in President Johnson against using his political capital to try to muscle civil rights legislation through Congress. Johnson’s reply was classic: “Hell, what’s the presidency for?”

Indeed, what is the presidency for? It is to lead America where it needs to go, even when the road is pockmarked by political obstruction and special interest roadblocks that always crop up as reasons not to do the right thing.

Today, we can no longer put off a presidential response to the increasing chaos in our climate. Our weather is out of whack. Climate change is happening, and fast.

It’s heartbreaking to see destructive forces hit families, farmers, business owners and communities across our country. It’s frustrating as the costs pile up to see next to nothing in response from Capitol Hill. And it’s ominous as the concentration of carbon dioxide in our atmosphere passes 400 parts per million – levels that haven’t been experienced in 3 million years, long before even cavemen walked the Earth.

Pouring more carbon pollution into the sky is setting the table for growing intensity of extreme weather, with more persistent drought, devastating wildfires, costly floods, scorching summers and storms that punish more with each punch.

We’ve got to stop making climate change worse. The president’s decision to double fuel efficiency standards in his first term ensures we’ll burn a lot less fossil fuels in the coming years. The next big step is to reduce carbon pollution from the nation’s power plants. They account for 40% of the carbon dioxide sent into our skies. That’s harming our environment and our communities.

Fortunately, the president has the power through the Clean Air Act to require dirty coal plants to clean up their carbon emissions. He can do so at a lower cost than many would expect and deliver greater benefits for our health and future.

He can set state-specific limits on carbon emissions. Then, states and power companies can work together to change their energy mix, relying on flexibility and innovation to curb carbon pollution while ramping up energy efficiency in homes and businesses.

Replacing dirty power with clean energy from renewable sources and energy efficiency will create jobs, boost our economy and save us money. But most important of all, it will protect our climate and our health.

The president has spoken well about our obligation to reduce the threat of climate change. Now we need him to tell us how he will fulfill that responsibility, to show the leadership he is capable of, to move beyond intellectual acknowledgment of the problem toward measurable steps that solve the environmental challenge of our time.

This, Mr. President, is what the presidency is for.

Robert Redford is a trustee of the Natural Resources Defense Council.

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