Change is the one constant

Fill in the blanks:

It is customary in the popular media and in many journal articles to cite a projected _________ figure as if it were a given, a figure so certain that it could virtually be used for long-range planning purposes. But we must carefully examine the assumptions behind such projections. And forecasts that ________ is going to level off or decline this century have been based on the assumption that the developing world will necessarily follow the path of the industrialized world. That is far from a sure bet.

That comes from an essay at Yale's e360.

Given that you're reading a blog concerned with climate change, you are excused if you slotted in "carbon emissions" or something similar. The correct answer is "population," but the author's argument is equally applicable to either issue. Carl Haub, senior demographer at the Population Reference Bureau, is simply pointing out that the experts on such matters are often wrong when they take current trendlines and extrapolate them decades into the future. And he writes that some of the assumptions built into the oft-cited UN estimates of a global population leveling off around 9.5 billion four decades from now are highly questionable.

The UN's middle-of-the-road assumption for sub-Saharan Africa -- that fertility rates will drop to 3.0 and population reach 2 billion by 2050 -- seem unrealistically low to me. More likely is the UN's high-end projection that sub-Saharan Africa's population will climb to 2.2 billion by 2050 and then continue to 4.8 billion by 2100. The dire consequences of such an increase are difficult to ponder. If sub-Saharan Africa is having trouble feeding and providing water to 880 million people today, what will the region be like in 90 years if the population increases five-fold -- particularly if, as projected, temperatures rise by 2 to 3 degrees C, worsening droughts?

Similarly, it is perhaps timely to point out that "business as usual" carbon emissions rates are almost certainly not going to continue for much longer. The cost of solar power and other clean renewables will almost certainly continue to fall (though not at current rates of more than 30% a year in the case of PV). But demand for power is continuing to rise (at less predictable rates thanks to economic instability). I just don't see how we can predict with any degree of confidence how many atoms of carbon we'll be spewing into the atmosphere 10 years from now let alone 50.

My point is, if we knew with a high degree of certainty what population or carbon emission trends were going to be, then we would be much better off, even if the trends were threatening and unavoidable. We could prepare and adapt. We'd know where to spend finite resources. The uncertainty matters almost as much as the trends themselves. From a political and business perspective, uncertainty is a bad thing. You don't want to spend billions on one technology unless you know the regulatory and financial context will support it.

We should do a better job emphasizing the monstrous amount of uncertainty that comes with such projections, and the climatological consequences of those figures.

Furthermore, surrendering control over how we respond to the threat of global warming (or population growth) to forces that are themselves unpredictable -- I'm talking about the free market if you hadn't figured it out -- doesn't make a whole lot of sense. It only multiplies the uncertainty. If, however, we can assemble a regulatory environment that takes advantage of those elements of the marketplace that do exhibit predictable behaviors, then we stand a fairly good chance of bending the curves that frighten us into something less fearsome.

This has bearing on the debate over cap-and-trade vs. taxes.