Eaarth—Making a Life on a Tough New Planet by @BillMcKibben—A New World (2)



 This is the second post in a series on the first chapter called A New World of Bill McKibben’s book Eaarth.

3. Chain of Causation

The next part of the first chapter called A New World deals with the next link in the chain of causation. If the rising global average temperatures are responsible for the various phenomena that are exhaustively described in the book and summarized in my previous blog post, then what is causing this rise in global average temperatures?

Figure 1. Global climate change “chain of causation”


The above diagram illustrates the next two links in the chain of causation: the increased global average temperatures are being caused by the rising levels of greenhouse gases that are released in the atmosphere, which in turn is being caused by the release of fossil fuels. The main greenhouse gas is carbon dioxide, although there are others, which are talked about in the next section of the chapter on feedback loops.

4. Concentration of carbon dioxide in the atmosphere

What is the “safe” level of carbon dioxide in the atmosphere? In pre-Industrial Revolution days, it was 250 parts per million or 225, and it is 390 ppm now. It was in December 2007 that James Hansen, the planet’s leading climatologist, gave a talk at the American Geophysical Union meeting in San Francisco where he concluded that the safe number was 350 ppm, much lower than the earlier proposed benchmarks of 450 or 550 ppm.

A level of 550 ppm gets into territory where there may be “feedback loops” that are discussed in the next section of the chapter (and the next post). I remember the cartoon-within-a-cartoon movie called Who Framed Roger Rabbit?, in which the temperature controller on the oven read, “warm … HOT … VOLCANO HEAT!”.  That’s the territory we are getting into after 550 ppm. This is my own shorthand way of understanding the various levels based on what was written in the book.

Figure 2. Concentration of Carbon Dioxide in the Atmosphere (measured in parts per million)

5. Mitigating Risk

One of the ways of mitigating the risk of rising global temperatures caused by the increase of greenhouse gases emissions would be to get the world’s governments to enact measures to reduce them. However, the measures increased so far are not sufficient. After the 2009 United Nations Climate Change Conference in Copenhagen a group from MIT called Climate Interactive calculated two scenarios:

  • If all government pledges AGREED TO at conference were enacted, then the world in 2100 would have more than 725 ppm carbon dioxide.
  • If all government pledges DEBATED BUT NOT AGREED TO at conference were enacted, then the world in 2100 would have 600 ppm carbon dioxide.

So if the response to climate change continues along its present course, therefore, we have two choices: HOT and VOLCANO HEAT.

The real problem about the area above 550 ppm comes from the process of feedback loops where the release of carbon dioxide sets up effects that in turn release OTHER greenhouse gases such as methane and peat which are even more powerful in their effect. That will be the subject of the next part of the chapter and the next post.

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