Log of Scoreboard Changes

We recently updated the Reference Scenarios (RS) to improve our methodology for downscaling from the more spatially aggregated data sources, i.e., SRES scenarios and EMF22 models. As a result, the global projections for BAU emissions remain largely unchanged but the allocation of future BAU emissions between C-ROADS regions has shifted. Consequently, pledges act on different regional baselines, resulting in different climate implications. Specifically, our new default, which remains based on SRES A1FI, now has a greater share of the global emissions coming from the Developed and Developing non-MEF regions. Just as before the RS updates, the trajectories of these regions under pledges decrease only slightly from their RS levels because pledges from these regions are a weighted average of all the member countries, many of which do not have any pledges. The higher reference scenario emissions for these regions thus give rise to higher emissions under pledge scenarios. Accordingly, the atmospheric concentrations, temperature change, and sea level rise with pledges are now all greater than previous Scoreboards because of our new default RS.

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Due to recent model improvements, the scoreboard and widget have been updated. While there have been several minor adjustments to the structure, the increase in reference scenario CO2 concentrations and temperature change relative to previous versions of C-ROADS primarily result from a few key advances.

The carbon cycle now includes a flux of C due to the oxidation of CH4 into the atmosphere. Also represented now are the fluxes of C from biomass and from humus, the sum of which are natural emissions of CH4. These natural emissions, converted to units of Mtons CH4 per year, replace the constant value previously used in the methane cycle.

Another major change in the model is the inclusion of carbon and methane-climate feedbacks in the system. While some of these feedbacks are set to zero in the reference run, the uptake of C to biomass and to the ocean now defaults to reflect the mean values of feedback from Friedlingstein et al., 2006.

Finally, the carbon and climate sectors, which were structured as 11 and 1 layers, respectively, now both have 5 layers. The eddy diffusion coefficient driving the movement of carbon through the deep ocean is now correlated with the movement of heat through the climate sector. As such, in the C-ROADS reference run, based on A1FI emissions, the 2100 CO2 concentration is 977 ppm, the CO2eq concentration is 1,444 ppm, and the temperature change from preindustrial levels is 5.0°C. These are increases from the values with the previous version of C-ROADS of 966 ppm, 1408 ppm, and 4.8°C, respectively.

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As there were no proposal updates resulting from the Bonn UNFCCC meeting, the only update to the June 2011 Scoreboard is a new potential proposal by the UK for reducing emissions 50% below 1990 by 2050.

Please also note that for Scoreboard purposes, the Monaco proposal is considered to be included in the France (and thus EU) commitments.

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The May 2011 Scoreboard reflects proposal updates resulting from the March 10, 2011 UNFCCC publication documenting Annex I emissions targets (http://unfccc.int/resource/docs/2011/sb/eng/inf01.pdf) and presentations to the UNFCCC meeting in Bangkok April 2011.

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Though there have been no new proposals released since August 2010, the March Scoreboard release includes an update to the default reference scenario for C-ROADS. For detailed information on these changes, please review this document.

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Starting with the August 2010 release, the format of the Scoreboard graphs have been updated to provide more alternatives for emissions trajectories after the last target year specified by countries or blocs. The "cap" designation indicates a scenario where emissions are held constant if they were falling during the approach to the target year and allowed to grow at the BAU rate if they were growing prior to the target year. The "BAU" designation assumes that BAU growth rates will resume after the target year, and the "continue decline" designation assumes emissions will continue to decrease at the rate at which emissions were falling in the approach to the target year. Our Scoreboard widget reflects the 4°C temperature change from the "Confirmed Proposals - cap" scenario.

Additionally, though there have been no changes to the list of publicly reported proposals, we have revised our proposal table so that countries included in the EU are no longer listed as their own entry.

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