It seems like that optimism is itself an ethical obligation. We'll only make the hard choices and the big sacrifices it takes to save our bacon if we believe it's not too late. We've come perilously close to large-scale self-destruction before and some would argue that we pulled back in time (there are still nuclear warheads out there, but the threat is arguably not what it once was, for instance), so it's not too hard to put a brave face on this self-imposed disaster deadline, too.
But this is a different kind of problem in that the climate is so large a system, with so many "pipelines" of energy, that the screwed-up inputs we put in during the last hundred years are still working their way through it, and the effects of things we did that long ago are still being felt.
One could make an analogy to medicine. Some conditions, when you first see visible, discomforting systems, it's still time to treat the underlying problem. Others, by the time you can feel the problem, the best you can do is limit the damage or ease the suffering, but the problem is too entrenched to be reversed. If the past threats we've placed on ourselves were more like the former case, this one is more like the latter.
There's no question that we have to act, and far, far more decisively than we are. That in itself is a source for a measure of despair. Consider this recent quote from Frank Lucas, ranking member of the House Agricultural Committee:
"During a time when our country is suffering from the worst recession in decades with double digit unemployment, when study after study predicts that cap and trade policies will cause higher energy costs and lost jobs, and when polls show that Americans are more concerned about those lost jobs than policies that address climate change--now is not the time for our President to make promises to the international community," Lucas said. "The U.S. should not act based on the expectations foreign governments may have regarding what the U.S. should do on climate change."In addition to being shortsighted (given how much hope there is that green investments could also revitalize the economy through expanding new sectors) it's achingly frustrating. If we made this our #1 priority it would probably still be too late, and Lucas wants to put a short-term (albeit serious) problem ahead of one whose effects will still shape the world in a hundred years.
But if you really take a frank look at the numbers, and you don't try to put a brave face on, the facts are clear. Even if we cut carbon emissions by double what Copenhagen is asking for (and probably won't get), and even if everyone went along with that, global temperatures will still rise within the next fifty years enough to cause irreversible changes in the biosphere.
Yes, this is going to change the shape of the globe. Low-lying cities like New Orleans will either be lost, or more likely, have even more resources poured into keeping them around rather than resettling them, making them increasingly expensive to maintain. Millions of people will have their lives displaced and destroyed, or will lose them. Countless artifacts of history and art will be endangered. The worldwide economy will be splintered in the attempt to adapt. And probably, humanity will find ways to deal with all of that (this is the thrust of a very glib article in Wired recently published).
But meanwhile, ecosystems will be lost irretrievably. Pollution problems will be concentrated. Plants and animals that are barely holding on with the little habitat they have left will lose migration corridors, be forced farther into smaller spaces as humans move to avoid places rendered uninhabitable, or lose habitat when climate change goes far faster than geological change.
This isn't just sentimental agony, the fear that we'll never hear the call of this bird or see the bloom of that flower or walk in the other kind of land again. It is also compound interest on our self-destruction. Economic problems with a lifespan measured in years caused us to create climate changes with a lifespan measured in decades, and dealing with those are going to cause us to create further damage to the biota whose problems will be measured in centuries.
One thing we can do is clench our teeth and put on the brave face and force some optimism that we can still avert some of the damage, maybe enough to save... this, or that, or the other thing. But only if we act decisively now. If I were a politician or someone with influence that's what I'd be doing. But inside, I'd be secretly thinking, "It's too late to really avoid the important damage, and the only consolation I have is that that will be someone else's problem."