Climate change is big, the biggest problem we've ever faced as a nation. In March, British economist Nicholas Stern said that inaction on climate change could cost the world one-third of its wealth. Last fall, the Global Carbon Project reported that world carbon emissions have risen and are in line with scientists' worst, most catastrophic scenarios for climate change. Bill McKibben has said, "If we're to have any chance of heading off catastrophic temperature increase, we have to do everything we can imagine." How big are our imaginations? What would it look like to do everything we can imagine?

As Congressional leaders and the coal industry try to tell Americans what is and is not possible to do to protect our communities from the disasters of climate change, Obama needs to call on all of us to put our hands and our imaginations to work. It's critical to have solid federal policy on climate change. But it's also important to imagine what will become possible as we tackle this challenge. And it's important for everyone to pitch in. That's the only way we'll solve a problem this large.

Obama has already ignited our imaginations, shaken up our sense of what is possible, and gotten us to consider the scope of the problems we face and our roles in solving them. In his November victory speech, he said, "I will ask you to join in the work of remaking this nation the only way it's been done in America for 221 years-block by block, brick by brick, callused hand by callused hand." He has brought people to his team like Van Jones, who ask us to consider the climate crisis as a vast opportunity to create green jobs: We'll need millions of people to get to work, tackling the enormity of building a whole new sustainable economy. And for months Obama has been airing ads calling on us to serve our communities. It's a start.

But there is more to do.

In the 1940s, the Roosevelt Administration called on Americans across the country to pitch in to the war effort, collect scrap metal, plant victory gardens. There was a "Don't Travel" campaign to get people to conserve gasoline and tires for the war. And the country came together behind a common cause and mission. The people who weathered this national crisis have been called the "Greatest Generation."

We have an opportunity to rise to greatness again. The crisis we face today is even larger than what our grandparents confronted. And it will take all of us planting our own gardens, conserving fuel and electricity, putting solar panels on our roofs, transforming our neighborhoods so we can walk and bike instead of drive, greening our buildings, and learning to save, recycle, and reuse.

Solutions will come from the grassroots, but it's not enough to leave climate change to a handful of volunteers. And it's not enough to leave a problem as dire as climate change to Congress alone. Obama needs to call on all of us, at every level. Our new president has more innate ability to inspire than perhaps any leader we've witnessed in decades. We've seen him call us to our best. It's time for him to do it again.

The most important thing Obama can do is unite us in a common mission: to do everything we can imagine to fight climate change.