Here's one example of the impacts of climate change on water supplies and national security that really paints a concrete (and scary) picture of the costs of not taking bold action now:
One thing that (the problem of water scarcity) leads to is (problems with) national security and failed state issues. I’ll give you one example: Pakistan, where the U.S. has invested enormous resources, is a nuclear-armed state with a rift with the Taliban, and it’s already a bit of a failing state. Soon it’s going to have one third of its water from in the Indus River—its main water lifeline—dry up from the lost (Himalayan) glacier melt. At the same time, its population is increasing by 30 percent. So in the next 15 years, we can imagine a country that’s already on the brink, dealing with a loss of 30 percent of its water while the population increases by 30 percent.
We see this coming, we know of the potential dangers that lurk around the corner, and that climate disruption is sure to bring unpleasant surprises. Yet America, the supposed leader of the free world, is also the world's greatest barrier to action on an issue that threatens to destabilize life as we know it?!
How much better would we feel about America -- and ourselves -- if we were leading on these issues via an Apollo Project-like energy and land use effort? Such an effort would galvanize the hopes of billions around the world, would revitalize our economy, would revolutionize our security, and perhaps most importantly, would rejuvenate our currently-downtrodden national psyche with a positive, hope-inspiring "we can do this!" mission.