Some of the nation\u0026#39;s leading climate scientists on Tuesday are urging President Obama to show his \u0026quot;climate convictions\u0026quot; and reject the tar sands-carrying Keystone XL pipeline.\r\nIn an open letter, the 18 scientists, including noted climate scientist James Hansen, Ralph Keeling of Scripps CO2 Program Scripps Institution of Oceanography and James Box of the Byrd Polar Research Center, write that rejecting the pipeline would be a \u0026quot;relatively easy\u0026quot; step to take to address the planet\u0026#39;s rising temperature.\r\nThe letter reads, in part:\r\n\r\n\u0026quot;As you may know, the U.S. has just recorded the hottest year in its history, beating the old mark by a full degree; the same year that saw the deep Midwest drought, and the fury of Hurricane Sandy, also witnessed the rapid and unprecedented melt of the Arctic ice pack. \u0026quot; [...]\r\n\u0026quot;Eighteen months ago some of us wrote you about the proposed Keystone XL tar sands pipeline, explaining why in our opinion its construction ran counter to both national and planetary interests. Nothing that has happened since has changed that evaluation; indeed, the year of review that you asked for on the project made it clear exactly how pressing the climate issue really is.\u0026quot;\r\n\r\nThe Keystone XL, which would carry tar sands crude out of Alberta into the US, has met fierce resistance by climate activists and members of communities in the pipeline\u0026#39;s path.\r\nIn a call for civil disobedience at the White House in Aug. of 2011, Hansen, author Naomi Klein and 350.org\u0026#39;s Bill McKibben were among those who called the Keystone XL \u0026quot;a fifteen hundred mile fuse to the biggest carbon bomb on the continent, a way to make it easier and faster to trigger the final overheating of our planet, the one place to which we are all indigenous. \u0026quot;\r\nTo make sure \u0026quot;the fuse to the biggest carbon bomb\u0026quot; is put out, climate activists are mobilizing for another mass action in DC on February 17.\u0026nbsp; Organizers write:\r\n\r\nJust over a year ago, 15,000 people surrounded the White House -- and President Obama listened, delaying the Keystone XL tar sands pipeline. This is our best chance to show the President how strong this movement has become since then -- sign up today.\r\n\r\nThe application for the pipeline by its company, TransCanada, is under review from the State Department with a decision likely by the end of the first quarter of 2013.