Linking Mid-century Targets to Long-Term Climate Change Outcomes
Abstract
We conducted a probabilistic analysis of the range of long-term climate options corresponding to various interim climate targets (i.e. mid-21st century targets for equivalent CO2 concentration). Interim targets have been proposed to bridge the gap between short- and long-term targets, address concern about the rate of temperature change, and provide guidance in planning for energy infrastructure while improved scientific understanding and political agreement on a long-term climate target have yet to be achieved. We focused on uncertainties in the climate system (including climate sensitivity, ocean diffusivity, and aerosol forcing) rather than in mitigation options in this analysis. We used the MAGICC model to estimate the mid-century global mean greenhouse gas concentrations and rates of temperature change as well as the long-term temperatures associated with a wide range of emissions scenarios. Our results allow the user to determine the rate of emissions reductions necessary after the interim target year (e.g. 2050) to achieve a particular long-term temperature target, for a range of interim concentrations or emissions and for a range of probability levels. For example, we found that for a mid-century target of 450 ppm, staying below an average temperature over the 22nd century of 3 degrees above pre-industrial with 75% probability would require post-2050 emissions reduction of 1%/year; a mid-century target of 550 ppm would require emissions reduction of more than 3.5%/year for the same temperature increase. We also conducted separate analyses considering different scenarios for emissions from deforestation and considering distinct rates of emissions reductions for non-CO2 gases versus CO2. Finally, we compare the probabilistic range of temperature projections using estimates of transient climate response (TCR) to that using the multiple climate parameters.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2006
- Bibcode:
- 2006AGUFMGC22A..07W
- Keywords:
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- 1610 Atmosphere (0315;
- 0325);
- 1626 Global climate models (3337;
- 4928);
- 1632 Land cover change;
- 6309 Decision making under uncertainty