Review of Hansen's "Storms of My Grandchildren"

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The book should probably be titled "Sea level of my Grandchildren", as Jim Hansen's main argument, that bad things will happen if CO2 is kept above 350ppm for too long, rests heavily on his conclusion that higher CO2 concentrations would drastically raise se level.  Hansen is one of the founding fathers of climate change science.  He wrote a seminal paper on CO2 and global warming (Hansen et al. 1981) and famously testified to Congress in 1988.  More recently, he became the target of one of the Bush administration's most publicized attempts to censor science.  This book weaves back and forth between the science of climate change and climate change politics and policies.  While he presents a view of how policymaking that few scientists get to see, I found his constant railing against special interests a bit tiresome, if not a tad naive.  On the science front, Hansen fairs better, although I wish he would stop apologizing when explaining something technical. 

The most interesting part of the book is how Hansen reaches the conclusion that 350 ppm is necessary to preserve society as we know it.  He begins with a very readable presentation of CO2's role in the earth's energy balance.  Essentially, CO2 reduces the ability of the planet to lose heat (received from the sun) through radiation.  From basic physics, warm bodies are more efficient radiators (thanks Dr. Maxwell!), so the Earth's temperature must rise until the balance of incoming to outgoing radiation is restored.  This argument is based on well-established physics, and the issue becomes how much of each gas is in the atmosphere and whether there are any feedbacks that could amplify or compensate for the warming.  For example, does warming increase water vapor in the atmosphere, leading to more warming?  Hansen does a good job presenting the uncertainty in these calculations, which lead to the basic conclusion that CO2 is the dominant factor determining global temperatures.  Although calculations and simple models play a role, Hansen's most convincing evidence comes from the paleorecord.  Ice cores from Greenland and Antarctica provide a long record of both CO2 levels (trapped in bubbles) and temperature (from oxygen isotopes).  These records show a strong association between temperature and CO2.  From this record, Hansen derives the earth's climate sensitivity, that is, the amount of temperature increase per unit of CO2 in the atmosphere.

Enter the grandchildren and their storms (or coastlines).  As I mentioned, feedbacks in the climate system are key to establishing the amount of warming and the amount of change.  Because ice and snow are white, they reflect incoming radiation at mostly short wavelengths that are not absorbed by the atmosphere.  Thus, ice and snow tend to cool the earth.  However,  warming near the poles will reduce the amount of ice, exposing more ocean and land.  Land will tend to reflect incoming radiation at longer wavelengths that can be absorbed by the atmosphere, leading to more warming.  The ocean itself will tend to warm up, making it harder to create ice the next year. The warming ocean is central to Hansen's concerns about his grandkids. Warmer waters around Greenland and Antarctica will tend to accelerate the melting of the ice sheets, something that is already occuring.  This adds water to the oceans and raises sea level.  Hansen finds plenty of evidence in the paleorecord to support major changes in sea level associated with warming.  He also notes that human societies developed in a period of unusually small changes in sea level.  He concludes that CO2 levels above 350 ppm will lead to increases in sea level faster than humans have ever experienced.

After reading the book, my impression is that Hansen is a very smart, if slightly strange, cat.  I think he makes a convincing case that climate change is happening, linked to CO2, and a significant threat to human societies.  I've now started working through Spencer's "The Great Global Warming Blunder."  Hopefully, I'll have something in a couple of weeks.

Late update.  I just watched Hansen on the David Letterman Show.  He was much less nerdy than I'd imagined from his book.  Not that I'm in any position to comment on another's nerdiness.

Hansen, J., Johnson, D., Lacis, A., Lebedeff, S., Lee, P., Rind, D. and Russell, G. (1981) Climate impact of increasing atmospheric carbon dioxide. Science, 213, 957-966.

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This page contains a single entry by Andy Pershing published on January 6, 2011 3:41 PM.

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