I'VE been doing a little reflecting on my view of the world, amid the (relative) quiet of the holidays, and it seems to me that my thinking about things has undergone a subtle shift. In a nutshell: I've become far less confident about our ability to accurately describe possible outcomes more than a decade out. Correspondingly, I've become increasingly sceptical of the value of analyses of decisions now that attempt to assess the costs and benefits of action over horizons any longer than a decade. I don't know quite when this happened, though I suspect that the euro crisis has had something to do with it. And I don't doubt that many of you have been thinking this way for ages. It's a new and uncomfortable development for me, though.

So when Tyler Cowen muses about whether it might not be better to break up the euro now, I have no idea how to begin assessing the idea. My sense is that this is not at all a good idea, because it's sure to be very unpleasant over the short to medium term, and that's as far out as we can reasonably hope to analyse. I find myself thinking about people who lived in the 1840s. What decisions should Europeans and Americans have been taking then? Might it have been a good idea to go ahead and break up the American union? Doing so might well have prevented a terrible war two decades later. On the other hand, had the union not stayed together and fought the Civil War, the South might have gone its own way and maintained the brutal institutions of slavery for far longer than it actually did. Or consider the revolutionary technological and economic changes which loomed ahead. How should an adult living in the 1840s have thought about humanity's choice to resist or accommodate such developments? In America, the answer seems clear; move forward 100 years and you find yourself in an age of unprecedented prosperity, a society as free and rich and healthy as it had ever been. In central Europe, on the other hand, the perspective might well have been very different. Move forward 100 years there and you find a landscape in ruins, across which 10% to 20% of the population had met a recent, untimely end, with more deaths to follow under the thumbs of authoritarian governments. Try to look back over the past two centuries and consider a cost-benefit analysis conducted for any number of with-hindsight-monumental decisions. It quickly makes a mockery of our efforts to take good choices now.

I find myself thinking about these things in particular with respect to climate change. Not long ago, Karl Smith at Modeled Behavior wrote a post arguing that global warming would likely have a number of nasty consequences, but that humanity's best policy response is to plow forward in pursuit of economic growth, including through the aggressive development of fossil fuel sources. It was not especially well received in some quarters; it got him labeled "sociopathic" on Twitter. Is his a ridiculous view? I think then about a recent post written by a colleague at Democracy in America, who ruminates on the world's failure to address climate change and says:

Maybe a hundred years down the line, nobody will look back at climate change as the most important issue of the early 21st century, because the damage will have been done, and the idea that it might have been prevented will seem absurd. Maybe the idea that Mali and Burkina Faso were once inhabited countries rather than empty deserts will seem queer, and the immiseration of huge numbers of stateless refugees thronging against the borders of the rich northern countries will be taken for granted. The absence of the polar ice cap and the submersion of Venice will have been normalised; nobody will think of these as live issues, no one will spend their time reproaching their forefathers, there'll be no moral dimension at all. We will have wrecked the planet, but our great-grandchildren won't care much, because they'll have been born into a planet already wrecked.

My colleague presents this as a depressing possibility, and indeed it would seem to be so. But turn again to those living 100 or 500 years ago. How would they have viewed civilisation today? Think of all the animals, languages, and societies that have since gone extinct. Modern lives might seem like a vision of hell. The coastal, urban corridor along which I live now is horribly changed from its condition a century ago. Those of us who live along it spend the vast majority of our time indoors and only rarely glimpse anything that could honestly be called nature. The food we eat is highly processed and often unidentifiable as one plant or animal versus another. Many of us rarely see many of our close friends and family, and communicate with them only through the tinny interfaces of our electronic devices. "Some life!", a resident of the past might conclude. Yet how many of us would switch places with those who lived centuries ago? A century from now, much more of the world will likely have been despoiled. Humans might live in underground bunkers eating lab-grown meat. But who's to say they won't prefer their lot to ours?

The preferences of future generations will necessarily reflect the world in which they find themselves; they cannot be compared to our own, anymore than the preferences of those living in 1700 would have meaning in today's world. What matters is the welfare of future generations. Preserving the earth as it is isn't a worthy goal; preserving growth in living standards is.

What might lurk on the other side of the dark curtain that prevents us from seeing more than a few years out? One possibility is that growth will continue, at a pace fast enough to ensure that however degraded the environment our descendents are better off than we are. There are three more worrying potential dynamics, however. One is that the growth rates of the past century are no longer sustainable, climate change or no. That would be very bad news; a world in which the pie is no longer getting larger is one in which countries can only have more at the expense of others. Conflict would be rampant in such a world. The good news is that this seems like an unlikely outcome. So long as the march of technological progress continues, humanity should continue to find ways to do more with less.

A second possibility is that growth will continue, but the costs of climate change will be sufficiently large to offset any gains. And a third is that growth will or won't continue, but it won't matter because the impact of climate change will be sufficiently large to render the planet uninhabitable to humans (or incompatible with life as we know it, at any rate).

If one believes that it's nearly useless to project more than a decade out, then it seems wisest to proceed from an insurance standpoint. It makes little sense to try and work out projected growth rates decades ahead, compute a social cost of carbon, apply standard discounting and put together a plan which attempts to maximise welfare for all generations, including the present one. It's absurd to do so. We can run the exercises in order to help us think through the issues, but there's little use in pretending that there's much more to it. Instead, one might argue, there are two thing which should take priority. First, it seems likely that in any set of conditions, the richest society will be best suited to adapt. As such, policy should be tailored around maximising medium-term growth potential. And second, society must aim to avoid scenarios to which it is fundamentally unable to adapt.

Translating these principles into action in the present, on matters involving real trade-offs, is no picnic. Oddly enough, a change in the way one looks at the long run doesn't necessarily change assessments of many specific policy proposals. Countries should try to boost growth. It's a good idea to price externalities and support broad-based research, and it's probably a good idea to also continue developing fossil fuel assets—the wealth such development generates enhances our ability to invest now and consume later. What seems clear from this perspective, however, is that America's present policy stance is really, really bad. If future wealth is the most important thing, then it makes little sense to borrow heavily from the future for current consumption. Insuring against catastrophe means trying to boost future wealth, and that means that if you're going to borrow, it's important to channel that borrowing into investment. The good thing current consumers get as compensation is the ability to burn away cheap fossil fuels. If disaster prevention is the key, by contrast, then consumers can borrow now for the purpose of consumption, but they must compensate the future by facing strict limits on carbon emissions.

Instead, America is consuming more than it can afford now, leaving the future less rich, while also pouring carbon into the atmosphere. That strategy only makes sense if destruction is already a foregone conclusion—if there will be no future to pay off the debt. Why should the world behave this way? I suppose one possibility is that there is less of a future for the median voter. Over the past 30 years, the age of the median American has risen from around 30 to near 40. The age of the median voter is higher still, and rising.

Ultimately, the first step toward addressing future ills is to behave as if there will, in fact, be a future. America's policy disagreements are not so much about what looms two and three decades ahead, or about how to weigh the welfare of those living at that time, but about whether to include the value of their lives in considerations of present policy choices at all.