The World at 350 ppm Carbon Dioxide

Posted by Indur Goklany

According to James Hansen, the Paul Revere of global warming, the safe level for CO2 may be 350 ppm. Hansen is concerned that “ice sheet disintegration, vegetation migration, and GHG release from soils, tundra or ocean sediments, may begin to come into play on time scales as short as centuries or less.”  But currently the atmospheric concentration is 385 ppm. The 350 ppm level was reached twenty years ago in 1988, the same year that James Hansen sounded the alarm over global warming at a Congressional hearing.

Is the world better off today compared to 1988?

Let’s check:

Much of these improvements are due to economic growth and agricultural activity that fueled the rise of CO2 concentrations beyond 350 ppm. Because of technological change, it is likely that a portion of these improvements would have occurred absent any economic growth (as pointed out in the book, The Improving State of the World ). But had CO2 concentrations been capped at 350 ppm, we would have to forgo many of the above improvements in the quality of life, and not only in the developing world.

But would we want to go back to the world of 1988 — or even 1998 for that matter?

If we can go back to 350 ppm without giving up the real and tangible advances in human well-being that have accrued since that “benchmark” was passed, I’d have nothing against that, but based on the precautionary principle, one needs a stronger reason than the speculative catastrophes that Hansen is concerned “may begin to come into play on time scales as short as centuries or less,” whatever that means.

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