sexta-feira, 11 de abril de 2014

Climate scientist Michael Mann: If we don’t Stop Now, we’ll surpass 2°C global warming

When will the global warming process, and all the damage it does, get out of control? This question is obviously the focus of considerable debate.
Lately the writing and thought of Guy McPherson is causing some controversy among climate thinkers and writers. McPherson’s predictions are at the extreme edge of cataclysm. For some of what McPherson is saying, scroll to the bottom of this piece and listen to the interview. The interviewer is Thom Hartmann, on his nightly TV show “The Big Picture”.
McPherson sees runaway global warming in this century due to a massive methane emission from the Arctic, especially Siberia, with warming even greater and faster (both degree and speed) far beyond what even I’ve been talking about. (For some background on methane as a greenhouse gas, go here.)

What do more mainstream climate scientists, like Dr. Michael Mann, predict?

As I said, there has been some discussion of McPherson among climate writers thanks to the Hartmann interview. Which has led many of us to consider a recent piece, published in the mainstream Scientific American, by Dr. Michael Mann. Mann is famous, against his will, for first having produced the Hockey Stick diagram, and then for being attacked verbally by deniers, and legally by Virginia AG Ken Cuccinelli, for his climate views.

This piece is adapted from something I contributed to one of those climate discussions. After it was noted that some well-respected climate scientists thought McPherson may be wrong on some of the science, the discussion turned to Mann’s article. (The issue with McPherson’s hypothesis, in part, involves the temperature and pressure conditions under which deep-underwater methane “ice” could convert to a gas in large enough quantities to cause the runaway effect, though other objections are raised as well. [Update: Do I disagree with McPherson? Too early to say. I haven't yet given it the study it deserves.])
Mann’s article itself is here, and it’s very well-written — not at all science-speak. Key to his piece is this diagram and its text. I’m including it below in a small version. If you click, a much larger and very readable version will open in a new tab.

Now note the last sentence on Dr. Mann’s chart (my emphasis):
These data therefore indicate that to reliably avoid two degrees C of warming [above pre-Industrial levels], CO2 levels should be held to 405 ppm (blue [line]) — barely above the 393 to 400 ppm levels observed in the past year.

Read more here.

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