AVOID 1: The economics and climate change impacts of various greenhouse gas emission pathways and a comparison between base line and policy emissions scenarios

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AVOID 1: The economics and climate change impacts of various greenhouse gas emission pathways and a comparison between base line and policy emissions scenarios

January 22, 2010
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Deliverable 1 of AVOID-WS1 produced emission scenarios that represented possible future global emission pathways for greenhouse gases during the 21st century. This was detailed in a simple fashion by varying three parameters: the year in which emissions peak globally, the rate of emission reduction (R), and the minimum level to which emissions are eventually reduced (H or L). The scenarios in deliverable 1 show emissions gradually deviating from a baseline, the A1B SRES scenario.

Deliverable 1 also produced the global climate change resulting from these various emission scenarios.

Deliverable 2 produced a literature review designed to provide an update on the key advances since the publication of IPCC AR4.

The analysis in deliverable 3 is based upon these scenarios and provides quantitative estimates of (i) the climate change impacts avoided by reducing the emissions relative to the baseline and (ii) the economic implications are of reducing these emissions relative to the baseline.

We calculate impacts averaged over three time periods:

2015-2044 (centred on 2030)
2035-2064 (centred on 2050)
2070-2099 (centred on 2085)

We drive the impacts with the median climate change outcome from the scenarios (from deliverable 1), and we use the downscaling model ClimGen, which is based on a simple pattern scaling approach, to produce climate change patterns on a 50x50km grid. Our default is to use HadCM3 derived pattern scaling. We also carry out two sensitivity studies (i) driving one of the scenarios with the 10% and 90% outcome, in order to understand the effect of uncertainty in climate sensitivity, ocean heat uptake and carbon cycle feedbacks (ii) driving one of the scenarios with an ECHAM4 derived pattern scaling, in order to understand the role of choice of GCM pattern.

The scenarios chosen for analysis in deliverable 3 have peak years of either 2016 or 2030. These scenarios are: 2030.R2.H, 2030.R5.L, 2016.R2.H, 2016.R4.L and 2016.R.Low. The emission profiles of these scenarios in absolute terms and also in terms of % emission reductions with respect to 1990 are shown in the Figure 1 and Table 1a and b below, together with the A1B reference scenario. Also shown for comparison are the baseline scenarios used by the AIM and E3MG economic models.

Many of the impacts and climate models used in AVOID WS1 are linked together in the integrated model CIAS (Warren et al 2008). This enables the avoided impacts from a wide range of scenarios to be deduced.