In this first set of blogs I have focused mostly on the science of climate change. The first couple talked about the IPCC report, and how it comes about, but since then, it has been mostly science. I have tried to introduce the science from a fundamental point of view, because the fundamentals are both powerful and relatively simple. Quickly, greenhouse gases hold energy close to the surface of the Earth for some amount of time. If we increase the amount of time that energy is held close to the surface of the Earth by increasing greenhouse gases, then the Earth's surface will get warmer. There are really only two ways that the Earth takes up energy from space (the Sun) and gives it back to space (infrared terrestrial radiation), and that is through absorption
of radiative energy. Of course, what happens with that extra energy held close to the Earth's surface is complex. The same is true for the carbon dioxide and other gases we are putting into the atmosphere; what happens is complex.
I think it is safe to argue that the Earth will heat enough to matter. Many argue that it already has. I generally say that the changes in climate will be enough to be disruptive. By disruptive, I mean that changes in the water cycle and temperature will be large enough to cause changes in the balances that we have grown accustomed to. It's reasonable to expect more heat waves, and perhaps changes in agricultural and ecosystems. In the past year the long-established growing charts
that appear in gardening books and on the back of seed packets have changed. If you look at the past record of climate and human behavior, we see evidence of climate-related disruption of society on both regional and continental scales.
So I mean disruptive in the sense that balances will change. One could image a scenario where, if you stand back far enough, positive and negative changes are both realized and cancel out. While it is reasonable to expect both winners and losers, there is no reason to expect the positive and negative changes to cancel out. Such impacts are not subject to the same type of conservation principle as, say, energy. If one considers sea level rise to be one of the most likely consequences of the warming Earth, it is difficult to imagine that there will a lot of winners from the sea encroaching on the land. (Dike building companies will likely do well.) Hence, at least in this case, one expects a trend of net societal loss. And if you get close enough to imagine that the changes take place across international borders, well, if the U.S. is a loser and Canada is a winner, will that not be disruptive?
We have these predictions of climate change that suggest a warming Earth and a whole array of correlated changes. We have a set of uncertainties. That warming has occurred and will continue to occur is quite certain. Exactly how, say, storm tracks and storm intensity will change is less certain. On one hand the predictions and observations drive us to do something. On the other hand the complexity of the problem, the fact that all elements of the economy and society are impacted, and the scientific uncertainty make it difficult to converge on what to do.
Traditionally, what to do is placed into two categories; I am explicitly eliminating the choice of "do nothing." These two categories are mitigation and adaptation. Mitigation is the idea of limiting climate change by limiting the amount of warming by limiting the emissions of industrially and agriculturally generated greenhouse gases. This is the idea of limiting carbon dioxide to some value that we determine can be tolerated. The amount of carbon dioxide that is often mentioned is, say, 450 to 550 parts per million (ppm).
We are close to 390 ppm today; prior to the industrial revolution we were at about 280 ppm. Adaptation is idea of preparing for or reacting to climate change. For instance, moving towns and cities away from the coast or increasing the use of air conditioning. Geo-engineering, the idea of trying to manage the climate, by for instance, increasing reflectivity of clouds through put salt in the atmosphere,
is sometimes viewed as a third option. Some classify geo-engineering as adaptation, some as mitigation; virtually all consider it to be, perhaps, risky.
To me, if you are out of the do nothing camp, then you are in both the mitigation and adaptation camps. I don't think it is wise to imagine letting carbon dioxide getting to 1200 ppm; hence, mitigation is called for. Carbon dioxide will almost surely get to 550 ppm, which will require adaptation. Geo-engineering? Do readers consider carbon sequestration geo-engineering? Policy? There is no one policy that solves this problem. Mitigation requires something in the flavor of global, long term policy. Adaptation will require policy of all different scales--land-use policy in coastal regions would be at the top of my list (irrespective of climate change!).