Thursday, January 11, 2007

Global Climate Change: An Accumulation of Cumulative Effects

Cumulative Effects
By J.B. Ruhl

It's going to be 75 degrees here this Saturday and Sunday (as it was last Saturday and Sunday). Granted, I live in Florida, but 75 degrees in January? So I couldn't help but think about the big cheese of all cumulative climate change. [Disclaimer: if you don't believe global climate change is afoot, or if you don't believe anthropogenic causes are at least in part behind it, you might want to surf on, though really you should read on.]

My 6th grader son knows the explanation for global climate change (GCC) is that we're emitting so much greenhouse gases that they are trapping heat in the atmosphere. But it's not that simple. Rather, GCC is a net effect of the effects of countless reactions set in motion by, among other things, increased greenhouse gas emissions. Some of the effects increase local or regional temperature, and some reduce it, in both cases on small incremental scales.

Take, for example, just one of the potential manifestations of GCC--increased fire frequency in the earth's boreal forests. Also known as the taiga, these are the lush coniferous forests situated in the high northern latitudes above the steppes and below the tundra. Research presented recently in Science (Randerson et al., 314:1130-32) examines the net effect of fires based on their many effects, some of which increase temperature (bad) and some of which decrease it (good). Fires release greenhouse gases (bad), but they also release aerosols (good or bad, depending), and deposit carbon the land's snow and ice surfaces, which reduces albedo (bad), yet they also can alter heat radiation effects of the burned ecosystem landscape (mostly good). So what is the net effect? The research suggests that it is to increase overall temperature immediately after a fire but to decrease it over an averaged 80-year period. So, to the extent greenhouse gas emissions trigger reactions that cause more fires in the boreal forests, in the long run the fires lead to a negative feedback effect.

Of course, the answer to GCC is not to ignite the boreal forests! The point is simply that GCC is very complex, and what we see as a net effect is in fact the accumulation of many cumulative effects. Moreover, the fact that greenhous gas emissions may be the significant driver in this system of effects does not mean we can say for sure what will happen were we able to reduce emissions. The system of effects that has been set in motion is neither linear nor reversible--it's not as if as we slowly work our way back to 1990 levels of greenhouse gases, the system retraces its steps as if rewinding a movie.

So what does this mean for policy? Two big picture observations:

1. As important as it is to focus on the big drivers in this system of systems--in particular, greenhouse gas emissions--it is also important for us to study and understand as much as we can about all of the other effects contributing to the net effect. The big drivers don't drive everything, and in any event we will never understand how to steer them. We need to understand that policies directed at a particular component of the system--even at the big drivers--may trigger effects elsewhere in the system that work in the opposite direction.

2. Recognizing that (a) we will never fully understand the whole system, and (b) we will never be able with perfect accuracy to predict the long-term impact of any particular policy measure on the system (much less on human systems such as the economy), we need to begin developing a legal infrastructure around the need to adapt to global climate change. This legal structure will not be about environmental policy per se, but rather about insurance, immigration, agriculture, tort liability, contracts law, social benefits policy, and so on. In short, we need a law of global climate change, not just law to stop global climate change.

Villanova law professor Joeseph Dellapenna sparked an interesting thread of e-mails on the environmental law professors' listserve by raising this subject, and it is clear that talk of adapting is anathema to many who want to hammer away at the big drivers in the system--in particular, to alter behavior leading to, and law governing, greenhouse gas emissions. And there is some reason to want to shy away from talk of adaptation, because people--Americans in particular--may be keen to the idea that if we can adapt, then we don't need to suffer the pain of working on the drivers. Reducing greenhouse gas emissions will be costly, they may say, so let's skip that step and just adapt to what comes from not doing so. People need to understand, however, that when we say "adapt" to GCC, we don't mean turning down the thermostat. We mean moving cities, moving people, changing the way we live--in other words, spending a lot of money and changing a lot of lifestyles. It will be vitally important, therefore, to develop models of the cost of adaptation based on futures with and without policies aimed at the drivers, to illustrate how much work on the drivers can save us in cost of adaptation. But it is equally important to develop models of how we can adapt given the likelihood that policies aimed at drivers will in many cases fail or be too costly to implement, as well as that even if we do tough it up and reduce greenhouse gas emissions by huge margins, we're unlikely to turn the corner on GCC effects for decades.

In other words, as in the jungle, and as in business, part of our global climate change policy must be to appreciate that we must adapt to imminent climate changes or die ignoring them.


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