Thursday, May 29, 2008

Books on Global Warming

Freeman Dyson reviews two books on global warming in a recent issue of The New York Review of Books. The first describes the global-warming problem as an economist sees it and is not concerned with the science of global warming or with the detailed estimation of the damage that it may do. It assumes that the science and the damage are specified, and compares the effectiveness of various policies for the allocation of economic resources in response. The second book is the record of a conference held at the Yale Center for the Study of Globalization in 2005. It is edited by Ernesto Zedillo, the head of the Yale Center, who served as president of Mexico from 1994 to 2000 and was chairman of the conference. I am not going to summarise the review here. What I want to discuss briefly, is an issue which Dyson brings up, which is not discussed in either of the books under review. He considers the Keeling graph which shows the fraction of carbon dioxide in the atmosphere as it varies month by month and year by year. It gives us our firmest and most accurate evidence of effects of human activities on our global environment. When we put together the evidence from the wiggles and the distribution of vegetation over the earth, it turns out that about 8 percent of the carbon dioxide in the atmosphere is absorbed by vegetation and returned to the atmosphere every year. This means that the average lifetime of a molecule of carbon dioxide in the atmosphere, before it is captured by vegetation and afterward released, is about twelve years. This fact, that the exchange of carbon between atmosphere and vegetation is rapid, is of fundamental importance to the long-range future of global warming. Dyson pins a lot of hope on biotechnology providing mankind with the wherewithal to create more carbon-eating trees. Here is his overview...(in the process he also takes a pot-shot at ethanol, as does Amartya Sen (see my previous post)). At this point I return to the Keeling graph, which demonstrates the strong coupling between atmosphere and plants. The wiggles in the graph show us that every carbon dioxide molecule in the atmosphere is incorporated in a plant within a time of the order of twelve years. Therefore, if we can control what the plants do with the carbon, the fate of the carbon in the atmosphere is in our hands. That is what Nordhaus meant when he mentioned "genetically engineered carbon-eating trees" as a low-cost backstop to global warming. The science and technology of genetic engineering are not yet ripe for large-scale use. We do not understand the language of the genome well enough to read and write it fluently. But the science is advancing rapidly, and the technology of reading and writing genomes is advancing even more rapidly. I consider it likely that we shall have "genetically engineered carbon-eating trees" within twenty years, and almost certainly within fifty years. Carbon-eating trees could convert most of the carbon that they absorb from the atmosphere into some chemically stable form and bury it underground. Or they could convert the carbon into liquid fuels and other useful chemicals. Biotechnology is enormously powerful, capable of burying or transforming any molecule of carbon dioxide that comes into its grasp. Keeling's wiggles prove that a big fraction of the carbon dioxide in the atmosphere comes within the grasp of biotechnology every decade. If one quarter of the world's forests were replanted with carbon-eating varieties of the same species, the forests would be preserved as ecological resources and as habitats for wildlife, and the carbon dioxide in the atmosphere would be reduced by half in about fifty years. It is likely that biotechnology will dominate our lives and our economic activities during the second half of the twenty-first century, just as computer technology dominated our lives and our economy during the second half of the twentieth. Biotechnology could be a great equalizer, spreading wealth over the world wherever there is land and air and water and sunlight. This has nothing to do with the misguided efforts that are now being made to reduce carbon emissions by growing corn and converting it into ethanol fuel. The ethanol program fails to reduce emissions and incidentally hurts poor people all over the world by raising the price of food. After we have mastered biotechnology, the rules of the climate game will be radically changed. In a world economy based on biotechnology, some low-cost and environmentally benign backstop to carbon emissions is likely to become a reality. Even by Dyson's optimistic estimates, it will be at least 50 years before bio-technology has mastered the technology to produce genetically engineered carbon-eating trees. If present day doomsday scenarios are to be believed, will that not be already too late for our beautiful blue planet? Dyson's claim of carbon-eating trees, have been debunked at the Real Climate site, the main point being what I have already discussed above - viz. the time scales involved and whether another 50 years of carbon pollution is something our planet can take, without us doing anything in the intervening period. There is also the important ethical problem of leaving the problems our generation has created for a future generation to handle. What kind of planet are we leaving our children? It's a pity that a top class scientist like Freeman Dyson should fall prey to the usual 'do nothing, its all a lot of hype, global warming is a myth' crowd.


Suvrat Kher said...

I agree. Dyson's timelines dont give me too much confidence. Warming is going to happen even if we eliminate emissions now, due to the present build up of CO2 and its long residence time. In 50 years with business as usual the amount of CO2 emitted may double or more depending upon the emissions trajectory taken. To nitpick Dyson he mentions that replanting a quarter of the worlds forest would reduce CO2 amounts in atmosphere by half in about 50 year. But half of what value? Todays or the one 50 years from now? That would require a much bigger land carbon reservoir than Dyson's estimate.

Plus there is the constant worry of all our forests being converted to GM trees. I doubt that will go down well with ecologists and environmentalists!!

Rahul Basu said...

Indeed, Dyson's somewhat optimistic and utopian scenario has been debunked at the Real Climate site which is mentioned in my updated post.