By Robert Redford

In laying out his progressive vision for national action on climate change, President Obama set a clear standard for the proposed Keystone XL tar sands pipeline.

It won’t be approved, he vowed last month, unless it “does not significantly exacerbate the problem of carbon pollution.”

Would it ever. Turns out, over its 50-year life, that tar sands pipeline would add as much carbon pollution to our atmosphere as every car in the United States kicks out in an entire year.

That’s significant. It would exacerbate the carbon pollution that’s driving climate chaos.

Any way you cut it, this tar sands pipeline flat out fails the president’s common-sense test. It needs to be denied.

A new economic and environmental analysis by the Natural Resources Defense Council explains why.

Much more carbon pollution is released from producing and refining tar sands crude than from conventional oil — 81 percent more, according to our State Department and the Environmental Protection Agency.

Over the life of the proposed Keystone XL, the difference comes to as much as 1.2 billion metric tons, the NRDC concludes, as much as the annual output of every car on the road in our country.

Think about that. We would have to park every single car in America for a full year to make up for the carbon pollution the tar sands pipeline would dump into our atmosphere.

Everybody in favor, raise your hand.

Nothing doing. We’re not about to green light that kind of carbon disaster and impose it on our kids.

And get ready for this argument from the industry: we’ll burn those tar sands with or without the Keystone XL pipeline.

No, we won’t — and don’t take my word for it.

Ever heard of Goldman Sachs? Standard & Poor’s? They’re just a couple of the bedrock sources of economic analysis that are already saying that, without the Keystone XL, much of the tar sands expansion just won’t happen.

Big oil companies want that pipeline so they can ship tar sands crude across the American heartland to Gulf Coast refineries and, from there, to lucrative markets overseas.

The Canadians don’t want tar sands shipped across their waterways, ranches, communities and farms. Well, neither do we.

Rail is not a viable option. It’s too expensive for tar sands.

RBC Capital Markets may have said it best: “Should Keystone XL be rejected, Canadian oil sands producers will need to rethink expansion plans, timelines and export pipe solutions.”

If you’ve never read an investment analysis before, that’s shorthand for “Forget about it.”

One thing we can’t forget, and that’s the debt we owe to our children, our obligation to leave them a country at least as sound as the one our forebears left us.

Climate change is the central environmental threat of our time.

We’re already paying a high price for it. Last year was the hottest on record across the continental United States. As a nation, we spent $140 billion on crop losses, wildfires, devastating floods and other extreme weather disasters related to climate change. Our government picked up the lion’s share of the tab — to the tune of $1,100, on average, for every taxpayer in the country.

Finally we have a president who wants to do something about it. For starters, let’s not make matters worse by expanding one of the most destructive, carbon-intensive industrial operations anywhere on Earth.

Let’s say no to the Keystone XL tar sands pipeline. To take action go to www.stoptar.org.