A Case for Climate Engineering (Boston Review Books)

This book is not a review of the different approaches to climate engineering but a reasonably complete discussion of solar radiation management. It could have been a long essay rather than a book.The author is clearly enamored with the lost cost, ease of implementation and tunability of SRM. But, IMHO, there is too little discussion of the different response of the earth to addition of CO2 versus reduction in solar radiation. The latter may enable adjustment of the average temperature of the earth, prevent melting of glaciers, halt sea level rise, etc. These are the most visible current issues in global warming due to CO2 increase. They are likely to dominate the political thinking and response, which IMHO may be very shortsighted.Here is just one issue that needs to be considered in much more depth before proceeding with any climate engineering. A major response to increased CO2 is acidification of the ocean. And, lowering the temperature will increase CO2 absorption into seawater, thus increasing acidification. The choice of a low cost, easily implemented SRM approach instead of a much higher cost, massive CO2 removal approach may actually worsen the calamity that humans are bringing on by making the oceans less able to support life.

After hearing about different strategies for stabilizing and cooling the atmosphere, this book provided clear answers. First, the use of jets to disperse sulfur dioxide into the stratosphere to create a multi-year semi-reflective sunshade is based on proven science and facts. As the NOVA show "Dimming the Sun" demonstrates, sulfur dioxide and sulfate aerosols can and do provide temporary cooling effects. This is incredibly important to maintain current sea levels, and avoid a massive, multi-trillion dollar misallocation of assets to build seawalls around the world's major cities. It is also extremely important that the world keeps the Arctic sea ice. Some scientists believe that the loss of Arctic sea ice, and a dark ocean surface there instead of a high albedo ice cover, would lead to as much global heating as all of the world's human-made CO2 to date (in the year 2013) -- a fully recognized global "tipping point".Second, Prof. Keith advises a gradual approach, to reduce about half of the global warming in any given year, so that the cooling would take place with minimal disruption of rainfall patterns (this would apparently imitate some of the natural releases of sulfur dioxide, but with less of the natural side-effects seen from events such as the Mt. Pinatubo eruption).Another informative aspect of this book is that it shows the amount of sulfur to be used, cost estimates for jets, and settles the concept of using ultra-long tubes attached to upper atmosphere helium balloons. The book also described technical reasons why the use of jets is far better. The large droplet vs. the small droplet challenge for sulfate aerosols is covered too.Moreover, Prof. Keith clearly argues that sulfur dioxide cooling needs to proceed in combination with the pursuit of ultra-low carbon baseload power stations, and that it is not a substitute for biosphere-friendly energy sources. The approach recommended in this book would buy time for the climate and, significantly, help to maintain the heat balance as coal is hopefully phased out. Few mention that the phase out of coal would result in less sulfur dioxide and aerosols, which would temporarily increase global temperatures (in fact, in the late 1990s as the US and Europe reduced coal pollution this actually happened for a time -- as shown in NOVA's "Dimming the Sun").In summary, this is a valuable book, with a high degree of clarity and eloquence.

Keith makes his case for climate engineering clearly. He recognizes the objections of critics, doesn't dismiss them, but responds. He is very clear that geoengineering should never, ever be used as a substitute for cutting carbon emissions. His position is that the risks and impacts of climate change may be so serious that geoengineering needs to be considered even though it has its own risks. To reduce those risks, he argues we need to begin some small scale testing if, for nothing else, to find out what should be avoided. For example, he wants to do an experiment to see if a tiny amount of sulphate released into the stratosphere depletes ozone in the area where it's released. If ozone is depleted, then the most discussed form of geoengineering, injecting sulphate aerosols into the stratosphere to reflect away some of the sun's radiation, would have to be ruled out as endangering the ozone layer that protects life on Earth from the UV-B radiation in sunlight. Many scientists who believe geoengineering needs to be explored see it as a last ditch emergency option that would only be used to head off an imminent climate catastrophe. Keith views it as an earlier use option to reduce the risks of climate change. After a decade or two of research and smaller scale testing, he would like to see us begin to gradually phase geoengineering in, reducing the rate of global warming rather than reversing it, watching all the while for negative impacts. Eventually, after preventing the Earth's average temperature from going too high, the geoengineering effort would be slowly phased down over several generations as greenhouse gas concentrations in the atmosphere declined. Another form of geoengineering, Carbon Dioxide Removal, might be used on a large scale to speed the process. Keith makes it clear that the technological challenge of doing geoengineering is not all that great and the cost is actually very low, but the challenge of objectively weighing risks is more difficult, and the governance issues involved are extremely difficult. He sees climate and geoengineering being as great a challenge to governance in the 21st century as nuclear weapons were in the 20th century.