This post has been updated below with news that Podesta will recuse himself from the Keystone XL decision.

President Obama is getting a new high-level adviser who cares a lot about climate change and doesn’t care much at all for the Keystone XL pipeline.

John Podesta is no stranger to the White House; he served as chief of staff to President Clinton. And he’s no stranger to the Obama team; he led the president’s transition into office after the 2008 election. Since then, he’s served as an “outside adviser,” The New York Times reports, and “has occasionally criticized the administration, if gently, from his perch as the founder and former president of the Center for American Progress, a center-left public policy research group that has provided personnel and policy ideas to the administration.”

For the coming year, he’ll be advising from the inside. He will help out on health care and “will focus in particular on climate change issues, a personal priority of Mr. Podesta’s,” according to the Times. Podesta is expected to encourage Obama to take action through his executive authority, as Congress is unwilling and unable to pass legislation on climate change or much else. “Podesta has been urging Obama for three years to use the full extent of his authority as president to go around Congress,” Politico reports.

Podesta is also an outspoken opponent of Keystone, and his move to the White House is making some Keystone boosters nervous, National Journal reports.

InsideClimate News has more:

His arrival comes just as the decision on TransCanada’s proposal to build a controversial pipeline to deliver tar sands crude from Alberta across the midsection of the United States approaches a critical turning point: the completion of a final environmental impact statement by the State Department. That will be followed by a crucial 90-day period in which Obama must decide whether the pipeline is in the U.S. national interest. …

Podesta has allied himself closely with some of [the environmentalists opposing the pipeline], including the wealthy investor Tom Steyer, who has been mobilizing opposition to the project. They appeared together at CAP’s conference to celebrate its 10th anniversary this fall.

Just last week, CAP co-sponsored a daylong conference with Steyer’s team in Georgetown to argue that the pipeline could not pass the litmus test Obama set back in June — that the Keystone could only be approved if it didn’t significantly exacerbate greenhouse gas emissions. …

[A]s the various interests in the Keystone decision make their final arguments at the White House, Podesta could not be better positioned as a particularly close adviser to voice his own views — and to debunk the arguments of those who favor the tar sands pipeline.

Will Podesta make the difference on Keystone? Don’t count on it. There are already plenty of people in the administration on both sides of the issue. Ultimately, the call is Obama’s alone.

But Podesta could make the difference on UFO issues

UPDATE, from The New Yorker:

A White House aide emailed late Tuesday that Podesta would recuse himself from working on the Keystone Pipeline decision.

“In discussions with Denis,” the aide said, speaking of White House Chief of Staff Denis McDonough, “John suggested that he not work on the Keystone Pipeline issue, in review at the State Department, given that the review is far along in the process and John’s views on this are well known. Denis agreed that was the best course of action.” Podesta’s climate change portfolio will therefore be limited largely to overseeing implementation of E.P.A. regulations, which are already moving along, and not the far more controversial and politically sensitive decision about the pipeline.

Still, Podesta is on record strongly opposing the pipeline. If Obama approves the project, he will have to do so knowing he is contradicting the assessment of his new climate-change adviser.

Another UPDATE, from The Washington Post, about how Podesta’s influence on environmental issues could extend beyond climate and energy:

John Podesta’s decision this week to join the White House staff will not only elevate the importance of climate change within the Obama administration, but it could have much broader implications for the president’s environmental policies.

Podesta played a critical role in shaping Bill Clinton’s environmental record while serving as White House chief of staff between 1998 and 2000, pushing for the designation of several national monuments as well as a national roadless rule that preserved tens of millions of acres of national forest. …

[H]e could influence the president’s decisions on issues … [such as] whether to block a massive copper and gold mine near Bristol Bay, Alaska.

Full disclosure: Grist periodically reprints posts from ClimateProgress, a Center for American Progress blog.