A reader writes:

While I appreciate someone on the right who is willing to engage honestly and intellectually with the issue of climate change, I think Manzi continues to make some basic category confusions about climate change, particularly as it concerns this line of argument. What I mean in this case is that Manzi is confusing specific predictions about the future with observation of long-term trends.

While I agree with him that predicting a specific scenario based on climate change is fruitless, or at least so vague as makes no difference from fruitless, we can easily see the OVERALL effects that climate change will have in the future. Thus we can predict the future of climate change based on current trends (e.g. Global temperature increase and lack of species diversity will have far more negative effects than positive ones, and these effects are both compound and cumulative.) without needing to resort to any specific scenario at all.

This idea of predicting without predicting is somewhat easier to see in the realm of, say, cultural history. Consider one of Obama's favorite quotations: "The arc of history is long, but it bends toward justice." I believe this to be true. All the evidence before me indicates that this is true. Thus, I can say with confidence that gay marriage will eventually be legalized in the United States. I can't use the abstract principle to construct a scenario-specific prediction about the exact socio-political conditions of our society when this legalization happens, but I can say from the abstract principle that this is the direction we are heading. I make this judgment based on a variety of political, cultural, and demographic factors.

Similarly, although I cannot make a bunch of concrete predictions about what the world will look like in 2400--or even in 2100, or any other specific time Manzi wants to name--I can definitely say that, to borrow a phrasing, "The arc of climate change is long, but it bends towards an inhospitable planet." The problem with the 2400 date isn't that it's impossible to predict that far, it's that the thinking embodied by that question is still short-term.

That might seem crazy at first blush, but 300 years is LESS TIME THAN OUR OWN VERY YOUNG COUNTRY HAS ALREADY EXISTED. Why are we putting an endpoint on human history at all? Isn't it of critical importance that we as humans find some way to exist in actual equilibrium with our planet, so that humanity can continue indefinitely? In 100 years or 300 years or 500 or 1000 years I plan to have descendants alive on this planet. Why should any of them be sacrificed on the altar of American consumption?