Stanford’s David Victor, Director of Stanford’s Program on Energy and Sustainable Development, did a Q&A interview with Foreign Affairs. Excerpt:
Will Rafey: Can geoengineering ever be a reliable substitute for a transition to renewable, sustainable energy?
A: Per my reply to Lucy Berman, there is no simple substitute for controlling emissions. Renewable energy could be a large part of that effort — and surely will be — but it is not the only option. Much higher energy efficiency must play a role; nuclear power can play a major role (if, at the same time, there is attention to controlling the risk of weapons proliferation); advanced coal-fired power plants that safely store most of their pollution underground can also play a role. Geoengineering could be, at best, a Plan B. And if we don’t invest to understand it and its flaws, it won’t even be Plan B.
(…) Mark Miller: United Nations International Panel on Climate Change (IPCC) data — for the Northern Hemisphere, at least — demonstrates that temperatures have cycled from a Medieval Warm Period, through a Little Ice Age, and since the turn of the last century, appear to be returning to the temperatures prevalent prior to 1600. CO2 can at most absorb only eight percent of the infrared spectrum, ergo the heat, radiating back from the earth in response to incident solar radiation. Man is responsible for about three percent of the CO2 in the atmosphere. So, at most, man is responsible for 0.24 percent of heat capture from the sun. Water vapor — clouds — is responsible for most of the heat capture. Given the interchange of water between the oceans and the atmosphere without any input from man, it is obvious that man’s influence on atmospheric temperature is negligible.
So my question is: Since we cannot appreciably affect the major mechanism of global warming — nor should we wish to — why should we even consider the diversion of scarce resources to geoengineering the climate content of CO2?
A: The science is a lot more definitive and not as you summarize it. What matters is the perturbation — the effect of human activities against the background of “normal” fluctuations in climate. The IPCC report that you cite makes that clear and does not support the math you outline. In fact, humans can have a major impact on the climate and are having that impact. First, the “natural” level of CO2 in the atmosphere is about 280 parts per million — a number that fluctuates, but was the number before the industrial revolution and is a good starting point. Since the industrial revolution, that number has risen about 100 parts per million. Essentially all of that rise (not three percent) is due to humans. Essentially all other greenhouse gases have risen in concentration as well; some have skyrocketed. Most or all of those increases are also traced straight back to humans. Temperature and other aspects of climate vary a lot, but overall temperature has risen, and most of that rise appears to be due to this accumulation of greenhouse gases in the atmosphere. You are right to note that CO2 is a “weak” greenhouse gas, but the volumes are so huge that even though it is weak, the overall effect on climate is huge. Water vapor is, as you note, the most important greenhouse gas, but humans (and nature) do not affect water vapor directly. Rather, the amount of water vapor in the atmosphere is a byproduct of how the climate system operates. Thus, what really matters when thinking about climate change is the original perturbation — the root cause that leads to changes in the whole climate system. That root cause is mainly the buildup of CO2 and other gases.
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