350 ppm - a line we've already crossed

This entry was posted on 1/2/2008 10:53 PM and is filed under Global Warming,Action.

From an article by Bill McKibben on Truthout.org:

    - "...what may turn out to be the most crucial development went largely unnoticed. It happened at an academic conclave in San Francisco. A NASA scientist named James Hansen offered a simple, straightforward and mind-blowing bottom line for the planet: 350, as in parts per million carbon dioxide in the atmosphere. It's a number that may make what happened in Washington and Bali seem quaint and nearly irrelevant. It's the number that may define our future.

    - Twenty years ago, Hansen kicked off this issue by testifying before Congress that the planet was warming and that people were the cause. At the time, we could only guess how much warming it would take to put us in real danger. Since the pre-Industrial Revolution concentration of carbon in the atmosphere was roughly 275 parts per million, scientists and policymakers focused on what would happen if that number doubled - 550 was a crude and mythical red line, but politicians and economists set about trying to see if we could stop short of that point. The answer was: not easily, but it could be done.

     - Consider: We're already at 383 parts per million, and it's knocking the planet off kilter in substantial ways. So, what does that mean?  (my bold)

     - The last time the Earth warmed two or three degrees Celsius - which is what 450 parts per million implies - sea levels rose by tens of meters, something that would shake the foundations of the human enterprise should it happen again."

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The next time anyone questions our need to take significant action to reduce our greenhouse gas emissions now, tell them about NASA scientist James Hansen, 1987, 350 ppm, and 383 ppm.

My question:  once we take our foot off the global warming train's "gas pedal" and significantly reduce greenhouse gas emissions, HOW LONG until the earth actually stops warming??  How fast is the train going and how much inertia does it have?

                                    

        

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Comments

• 1/3/2008 7:49 PM Jim Blair wrote:
  "My question: once we take our foot off the global warming train's "gas pedal" and significantly reduce greenhouse gas emissions, HOW LONG until the earth actually stops warming??....."
  
  Hi,
  
  The estimates are pessimistic.
  
  http://www.synapse9.com/design/ClimateLags.pdf
  
  And yet we continue to build more coal power plants. Perhaps future power growth could be supplied by wind and solar if we really pushed those with your tax shift.
  
  But the only realistic way to shut down existing coal plants would be to replace them with nuclear ones. And the environmentalists would not permit that.
  Reply to this
  1. 1/3/2008 9:16 PM Paul Riehemann wrote:
     
     Thanks for sharing this.  I encourage all to read this one page document (particularly our federally elected representatives and candidates for President):
     
     http://www.synapse9.com/design/ClimateLags.pdf
     
     The graph is from an 2001 IPCC report (the scientists that just won the Nobel prize with Al Gore) and the text below the graph is from the Centre for Environmental Management, School of Geography, University of Nottingham (excerpt below):
     
     "The key point this model illustrates is the fact that the time lags between mitigation

     actions and a system response in the biophysical systems are likely to be very long and varied.

     Even if the stabilization of CO2 concentrations in the atmosphere is achieved, this will only

     result in a gradual leveling off of the temperature increase (red curve), with a stabilization after

     an additional time lag of 50 – 100 years. The temperature increase before this leveling off will

     cause a rise of sea levels by thermal expansion of water that will continue for many centuries

     after the stabilization of GHG and temperature (blue solid curve). If we also consider the effect

     on the polar ice caps of the temperature increase, the sea level rise is likely to continue over

     millennia (blue dashed curve)."
     

     
     Reply to this
• 1/5/2008 3:42 PM Jim Blair wrote:
  Hi,
  
  The latest Scientific American has a proposal for replacing coal and natural gas with solar. There is a summary and some discussion at:
  
  http://www.earthportal.org/forum/?p=423#comment-1609
  
  My comments are included
  Reply to this

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