Yesterday, I stood in the warm Washington sunshine and joined thousands of peaceful demonstrators as we surrounded the White House in a shout out for climate justice. We were there -- 12,000 of us from all over North America -- to urge President Barack Obama to say no to the highly controversial Keystone XL, a proposed pipeline that would carry bitumen -- the dirtiest oil on earth -- from the tar sands of Northern Alberta over an ancient aquifer and prime farmland to the Texas Gulf Coast for refining. American citizens and communities along the pipeline's path have joined forces with environmentalists, scientists, and First Nations groups on both sides of the border to mount a fierce opposition to the project.

The Canadian government has given the go-ahead for Keystone. The State Department has weighed in with its opinion (in favour), as has the Environmental Protection Agency (opposed). The decision to give TransCanada the go-ahead for its pipeline, or not, rests entirely with President Obama. He is supposed to reveal his decision this month.

Until recently, the common wisdom has been that the president would reluctantly agree to the pipeline because of the demand for domestic jobs and the call for the U.S. to secure more energy supplies here in North America. But the latter argument has been turned on its head with reports that much of the Canadian tar sands oil will actually be exported to Europe after it is refined in the U.S.

And even the president admits that the jobs issue must be weighed against environmental concerns. Last week, he went on Nebraska TV to empathize with the growing opposition in that state to the pipeline: "We don't want, for example, aquifers that are adversely affected." President Obama was referring to the Ogallala Aquifer, a major fossil aquifer already in distress from over pumping that has become a flashpoint for opposition over fears that a spill could irreversibly damage this vital water source. In fact, Nebraska state legislators have recently moved to block the project altogether in their state, a move that would force the re-routing of the pipeline and perhaps result in its cancellation altogether.

The president and the energy industry have clearly noted the sustained opposition in the U.S. and Canada. For two weeks in late August, hundreds of peaceful demonstrators deliberately got arrested in an act of non-violent civil disobedience in front of the White House. And in Canada in late September, close to 200 Canadians, including myself, got arrested for crossing a police barrier on Parliament Hill in a similar protest. The Canadian government has also noticed the increased opposition and has upped the ante with expensive advertising on American television praising the tar sands as a safe and "ethical" energy source for the U.S. Clearly the stakes are growing and the turn-out shows that the opposition to not only Keystone, but the expansion of the tar sands, will not stop growing.

The atmosphere here was joyful, the speeches powerful, the mood hopeful. I addressed the demonstrators and in my remarks, I assured them that the majority of Canadians want a safe energy future and support policies that promote climate justice. I told them about the damage done to the water of Northern Alberta -- damage that will come to Texas and the Great Lakes and other sites in the U.S. as these pipelines spread across their country and ours like a toxic board game of snakes and ladders. I told them about the harm done to the First Nations communities that live downstream from the tar sands. I told them what might happen if there are spills along the route as we have already seen 14 serious spills in the first phase of the project.

I return home now filled with hope. And not just about the possibility of winning this fight. I am filled with hope at the number and diversity of people I met and continue to meet around the world and the coalitions and networks we are building. There may be many differences among us, but we know that the current model of unfettered market growth is killing the planet and crating class warfare unlike anything we have seen in modern times. I am hopeful because I see an articulation of an alternative as we struggle to find a better way of living with one another in harmony and stepping more lightly on this fragile planet that give us life.