Five years ago, when climate activist Bill McKibben was asked what the three most important things were that people could do to combat climate change, he replied, “One: Organize. Two: Organize. Three: Organize. And if you still have some energy left over after that, by all means, change the light bulbs.”

McKibben is getting used to rallying big crowds. And now, 20 years after he first started writing and lecturing extensively about the science and implications of climate change, the founder of 350.org faced his biggest crowd yet on Sunday at the Forward on Climate Change Rally and March in Washington D.C. He was visibly moved.

Since this past summer, climate change has become less of an abstraction for many people, including those in the path of Superstorm Sandy. There are scientific numbers to back up the anecdotal evidence of disaster: 5 percent more moisture in the atmosphere is contributing to more severe summer and winter storms, for example. These numbers are immune to politics, even though some people want to politicize climate change. “Physics and chemistry don’t care about politics,” McKibben will often say.

Politics is an unfortunate reality to be addressed, however, and Van Jones summed it up like this at the Forward on Climate rally: “In this town [Washington D.C.], if you don’t fight for what you want, you deserve what you get.”

It was a sentence that resonated with the 50,000 of us who braved the icy winds in Washington that day in order to send a message to President Obama about the Keystone XL pipeline. Jones referred to his impending decision about the pipeline as the only decision that anyone will really care about in 20 years, a decision that could undo much of the legacy of his presidency by green-lighting the huge tar sands project that McKibben likened to “lighting the fuse of a carbon bomb”.

Tar sands are a far different product than crude oil, in a few words. They are a product that requires destruction of huge boreal forests to mine, resource-intensive activity to refine, and toxic, corrosive additives to transport. There is no known way to clean a tar sands spill in a waterway. Representatives of the First Nations of Canada spoke at the rally of the cancers and illnesses that are inflicting their people who live in the areas being refined, even as the government of Canada ignores their pleas to protect their land, water and people.

One of the biggest messages out of the day was that a decision to allow the Keystone XL project to continue, and for the government of Canada and oil giants like Exxon to profit from the mining of tar sands, comes at the expense of not only the people, land and water who are in the immediate path of the project. Jim Hansen of NASA stated that the beginning of the mass use of tar sands for energy will mean “game over for the planet” in terms of stopping climate change, and the irrevocable changes it will bring and is bringing right now.

Not only is it a rash decision for our future, but one that will not even benefit the United States in any short-term fashion. This product is not meant to help North America become free of foreign sources of petroleum, but is destined for fossil fuel-hungry foreign markets. Remember that when the oil industry tries to say otherwise.

We are fighting for our existence, or even some semblance of the life we have known on our only planet home. Our question is this: How is it that we can continue as a species, and a species capable of empathy and rational thought, to allow greed, inertia, and denial to prevent action on a true planetary emergency? The answer is: We can’t. We won’t.

A recent Windham Town Council meeting featured oil industry executives who questioned the agenda of environmentalists. I choked on the sentiment. It was tragic and funny, all at once.

My motivation is a sustainable way of life that benefits the planet, and finding a way to the very survival of my children, and their children’s children. Guilty as charged. And I am not alone.

Helyne May is a resident of Windham.