February 13, 2008
How Big a Problem is Global Warming?
According to the IPCC, the UN body charged with assessing climate change, there is a 90% certainty that human action is warming the planet, and that without serious changes in our energy systems, further significant warming will occur this century. To stop this, we would need to fundamentally, and expensively, transform how all nations generate and consume energy. The cost of such a change would be in trillions of dollars, spread over many years, and there would be a likely reduction in the speed of economic growth, making generations to come not as wealthy as they otherwise would have become.
Needless to say, the decision to address this problem should not be undertaken lightly. Unfortunately, the debate has become highly political, with scientific nuance and rational judgment often ditched in favor of extreme positions. Some on the environmental side argue that we are already on the verge of a global catastrophe that will cause all sorts of havoc with both societies and the natural world. Some skeptics deny that any global climate change has even occurred, and suggest that the entire case for global warming is fabricated with cooked evidence.
What we do know for certain is that carbon dioxide is a gas that does trap solar radiation, and tends to raise the temperature of the Earth. We also know that use of fossil fuels results in the massive release of carbon dioxide. From a baseline level of 320 parts per million in 1900, carbon dioxide in the atmosphere has risen to 380 ppm. According to the “business as usual” scenario that the IPCC generated, this level will rise to about 800 ppm by the end of this century. We also know that in the 20th century, the Earth’s climate warmed by about 0.8 degree centigrade, although much of that occurred before 1940, and then the climate cooled slightly, before warming began again about 1975. But now comes the hard part. What would the effect of that future rise in carbon dioxide be on the climate of the Earth, and what would be the real world consequences of those climate changes?
This is where the true answer is “we don’t know”. Unfortunately, proponents of immediate action have taken to claiming that we do know, that it would be a very significant amount of warming (perhaps 5 degrees centigrade), and that we need to act immediately to stop it before catastrophic changes become inevitable. Critics have raised a number of serious questions, but their complaints have not been addressed fully, for reasons that are mostly political.
There are some serious questions that need to be answered before it becomes sensible to engage in highly expensive actions that will harm both developed and developing economies. The IPCC scenarios themselves have a couple of serious problems. First, the total global emissions projected for the century are probably exaggerated. This is for three reasons. The IPCC overestimates human population growth (by about a billion people compared with the UN projections). It also overestimates the amount of economic growth that will happen in the developing world due to a very silly error. The IPCC used market exchange rates to measure the size of poor economies in dollar terms, rather than using purchasing power equivalents. Such an error vastly underestimates the size of Third World economies, including China and India. As the IPCC assumes these countries will catch up with the developed world over the next hundred years, the choice of an artificially low baseline results in substantially overestimated subsequent growth.
Finally, the IPCC business as usual scenario simply ignored the fact that some action to reduce greenhouse gases will occur, and that the rapidly falling prices of renewables like solar and wind power will gradually result in a shift to these power sources over the next 75 years for purely economic reasons. Reasonable assumptions about all of these issues would substantially cut the long run carbon dioxide emissions projected, even without any drastic action.
Another set of issues has to do with the computer models that the IPCC is relying on to make its predictions. How do we know that these models are in fact accurate in any way? None has ever been tested, which is the basis of any true scientific validation. They all involve idiosyncratic tweaks and fudges to make them work. And they are not able to model clouds and water vapor, which would be critical to any realistic model of Earth’s climate. So if these computer programs cannot be trusted, what are we to make of their outputs, and how can we justify turning our world upside down based on them? Each of these programs is proprietary, and the centers that have created them do not fully disclose their inner workings to allow outsiders to comment on them.
Finally, the data of the last ten years has not been as alarmist as the IPCC projections would have one expect. Since 2000, atmospheric carbon dioxide concentration has been rising much less rapidly than the “business as usual” scenario projected, only 16 ppm instead of the expected 24 ppm. Carbon dioxide levels are rising about 20 ppm per decade currently; at that rate levels will only reach 580 by 2100, which many scientists consider “safe”. In addition, instead of rising by about 0.5 degrees centigrade, as the IPCC predicted, average global temperatures have been in a downtrend since 2000, with 2008 continuing that trend. Polar sea ice is back to its long run average this winter. Critics contend that the climate models are flawed, that they all fundamentally run “hot”. This means that they overstate how much warming a given rise in carbon dioxide will generate. If so, that would also suggest that the IPCC scenario is overcooked.
What is the responsibility of today’s world to fix a problem that may or may not materialize a hundred years from now? To what extent should people in 1909 have anticipated our world and sacrificed then to allow us to avoid certain assumed problems today? Conversely, how can we justify spending resources on fixing a problem for the distant future, while not providing enough funds to fix the crushing problems, like AIDS or natural disasters or malaria, that kill people today? This is not a call for doing nothing, but rather a suggestion that we think carefully and choose wisely before we act. Perhaps we should create the basic framework to address the problems, such as enacting a very modest carbon tax, or creating a very loose global cap and trade system, but without taking harsh action immediately. Boosting investment in renewables, and especially in research into clean sources of energy makes great sense. As does investing in energy efficiency and conservation. Finally, doing research into geo-engineering options, which could be a final safety net that could be used if in fact things turn out badly, would be good policy.