<![CDATA[Grist - Comment Feed for 47 groups urge Obama to endorse 2-degree C warming threshold]]> Grist Comment Feed en Comment #1 by Earl Killian http://www.grist.org/article/2009-07-01-obama-two-degrees/ Wed, 01 Jul 2009 20:17:39 -0700 http://www.grist.org/article/2009-07-01-obama-two-degrees/1 We passed 2°C a while ago, if you don't count air pollution. In other words, keeping under 2°C means a permanent committment to polluting our air. Read the abstract of http://www.pnas.org/content/105/38/14245.full for more information:

The observed increase in the concentration of greenhouse gases (GHGs) since the preindustrial era has most likely committed the world to a warming of 2.4°C (1.4°C to 4.3°C) above the preindustrial surface temperatures. The committed warming is inferred from the most recent Intergovernmental Panel on Climate Change (IPCC) estimates of the greenhouse forcing and climate sensitivity. The estimated warming of 2.4°C is the equilibrium warming above preindustrial temperatures that the world will observe even if GHG concentrations are held fixed at their 2005 concentration levels but without any other anthropogenic forcing such as the cooling effect of aerosols. The range of 1.4°C to 4.3°C in the committed warming overlaps and surpasses the currently perceived threshold range of 1°C to 3°C for dangerous anthropogenic interference with many of the climate-tipping elements such as the summer arctic sea ice, Himalayan–Tibetan glaciers, and the Greenland Ice Sheet. IPCC models suggest that ≈25% (0.6°C) of the committed warming has been realized as of now. About 90% or more of the rest of the committed warming of 1.6°C will unfold during the 21st century, determined by the rate of the unmasking of the aerosol cooling effect by air pollution abatement laws and by the rate of release of the GHGs-forcing stored in the oceans. The accompanying sea-level rise can continue for more than several centuries. Lastly, even the most aggressive CO2 mitigation steps as envisioned now can only limit further additions to the committed warming, but not reduce the already committed GHGs warming of 2.4°C.

]]> We passed 2°C a while ago, if you don't count air pollution. In other words, keeping under 2°C means a permanent committment to polluting our air. Read the abstract of http://www.pnas.org/content/105/38/14245.full for more information:

The observed increase in the concentration of greenhouse gases (GHGs) since the preindustrial era has most likely committed the world to a warming of 2.4°C (1.4°C to 4.3°C) above the preindustrial surface temperatures. The committed warming is inferred from the most recent Intergovernmental Panel on Climate Change (IPCC) estimates of the greenhouse forcing and climate sensitivity. The estimated warming of 2.4°C is the equilibrium warming above preindustrial temperatures that the world will observe even if GHG concentrations are held fixed at their 2005 concentration levels but without any other anthropogenic forcing such as the cooling effect of aerosols. The range of 1.4°C to 4.3°C in the committed warming overlaps and surpasses the currently perceived threshold range of 1°C to 3°C for dangerous anthropogenic interference with many of the climate-tipping elements such as the summer arctic sea ice, Himalayan–Tibetan glaciers, and the Greenland Ice Sheet. IPCC models suggest that ≈25% (0.6°C) of the committed warming has been realized as of now. About 90% or more of the rest of the committed warming of 1.6°C will unfold during the 21st century, determined by the rate of the unmasking of the aerosol cooling effect by air pollution abatement laws and by the rate of release of the GHGs-forcing stored in the oceans. The accompanying sea-level rise can continue for more than several centuries. Lastly, even the most aggressive CO2 mitigation steps as envisioned now can only limit further additions to the committed warming, but not reduce the already committed GHGs warming of 2.4°C.

]]> Comment #2 by Clifford Wells http://www.grist.org/article/2009-07-01-obama-two-degrees/ Thu, 02 Jul 2009 11:23:22 -0700 http://www.grist.org/article/2009-07-01-obama-two-degrees/2 Let me ask a theoretical question.  If we banned all CO2 right now, not a single extra ton, what would happen? 

Part of the answer is that the mean residence time for CO2 can be decades or even centuries, although such numbers can be disputed.  Obviously, it is unlike aerosol and sulfur compounds that settle or are scrubbed from the atmosphere in days or weeks or months. 

Houston we have a problem.

My point is that given the long residence times for CO2 and lag in temperature effects, "two degrees" doesn't make a lot of sense.  Could what we have already emitted into the atmosphere add two degrees?  I don't think the models are very good at that, since some tipping points and feedbacks may have been crossed already.  I declare "mass mumbo jumbo of the third degree!"  Haha.

Be careful when you want to set goals for CO2 and climate change in degrees.  They are NOT linear, although are correlated and plausible.  Think about that.  What if the only additional man-made CO2 was from animals when they exhale?

]]> Let me ask a theoretical question.  If we banned all CO2 right now, not a single extra ton, what would happen? 

Part of the answer is that the mean residence time for CO2 can be decades or even centuries, although such numbers can be disputed.  Obviously, it is unlike aerosol and sulfur compounds that settle or are scrubbed from the atmosphere in days or weeks or months. 

Houston we have a problem.

My point is that given the long residence times for CO2 and lag in temperature effects, "two degrees" doesn't make a lot of sense.  Could what we have already emitted into the atmosphere add two degrees?  I don't think the models are very good at that, since some tipping points and feedbacks may have been crossed already.  I declare "mass mumbo jumbo of the third degree!"  Haha.

Be careful when you want to set goals for CO2 and climate change in degrees.  They are NOT linear, although are correlated and plausible.  Think about that.  What if the only additional man-made CO2 was from animals when they exhale?

]]> Comment #3 by Salzman http://www.grist.org/article/2009-07-01-obama-two-degrees/ Thu, 02 Jul 2009 12:32:25 -0700 http://www.grist.org/article/2009-07-01-obama-two-degrees/3 Comment #4 by Peter Wood http://www.grist.org/article/2009-07-01-obama-two-degrees/ Sat, 04 Jul 2009 03:05:47 -0700 http://www.grist.org/article/2009-07-01-obama-two-degrees/4 We should have a global emissions budget that is consistent with a significantly greater than 50% probability of staying below 2 degrees. A 50% chance of exceeding 2 degrees (something being discussed in the current UNFCCC negotiating text) would be associated with some very serious risks.

]]> We should have a global emissions budget that is consistent with a significantly greater than 50% probability of staying below 2 degrees. A 50% chance of exceeding 2 degrees (something being discussed in the current UNFCCC negotiating text) would be associated with some very serious risks.

]]> Comment #5 by Username http://www.grist.org/article/2009-07-01-obama-two-degrees/ Tue, 14 Jul 2009 10:25:09 -0700 http://www.grist.org/article/2009-07-01-obama-two-degrees/5 It looks pretty bad.

]]> It looks pretty bad.

]]>