The U.S. State Department finally has given the Keystone XL pipeline an unexpectedly “green” light. In a Jan. 31 report, the agency found the pipeline wouldn’t cause significant environmental damage. It wouldn’t prompt more oil extraction. It wouldn’t increase demand at U.S. refineries. And, surely to the shock of many opponents of the long-proposed pipeline, its construction actually would lead to fewer greenhouse gas emissions than the likely alternatives for moving oil.

The State Department didn’t formally approve the project, but it did answer the key environmental concerns that President Obama raised when he put a stall on the project last June:

No, the pipeline would not be the environmental horror opponents allege. Yes, it would have a significant economic impact. It would create jobs.

The Obama administration should promptly approve Keystone XL.

Keystone XL would link the rich oil sands of inland Canada to U.S. refineries and ports at the Gulf of Mexico. That is, the pipeline would be a safer way to move oil from one part of North America to another — oil that now moves primarily by barge, rail and truck.

Yet the Keystone XL project remains in limbo five years after backers first sought approval from Washington. The pipeline plan divides two Democratic constituencies: labor unions that want the job creation, and environmental groups opposed to further development of fossil-fuel resources. No matter what Washington decides, Canada will extract this oil and consumers somewhere will use it; the question is whether it goes to U.S. refineries or to markets in China or elsewhere.

What’s most striking in the State Department report appears deep in the fourth of its 11 volumes, under the heading Greenhouse Gas Impacts. Three scenarios if the pipeline isn’t built:

• If the oil instead moves to refineries by rail and tanker, greenhouse-gas emissions would be 27.8 percent higher.

• If the oil is transported by train to existing pipelines, emissions would be 39.7 percent higher.

• And if the oil goes to the Gulf solely by train, emissions would be 41.8 percent higher.

The obvious conclusion: The Obama administration should strike a blow for environmentalism and approve the Keystone XL project.