Authors: Nathan Rive Asbjørn Torvanger Terje Berntsen Steffen Kallbekken
Publish Date: 2007/03/10
Volume: 82, Issue: 3-4, Pages: 373-391
Abstract
The question of appropriate timing and stringency of future greenhouse gas GHG emission reductions remains an issue in the discussion of mitigation responses to the climate change problem It has been argued that our nearterm action should be guided by a longterm vision for the climate possibly a longterm temperature target In this paper we review proposals for longterm climate targets to avoid ‘dangerous’ climate change Using probability estimates of climate sensitivity from the literature we then generate probabilistic emissions scenarios that satisfy temperature targets of 20 25 and 30°C above preindustrial levels with no overshoot Our interest is in the implications of these targets on abatement requirements over the next 50 years If we allow global industrial GHG emissions to peak in 2025 at 14 GtCeq and wish to achieve a 20°C target with at least 50 certainty we find that the low sensitivity estimate in the literature suggests our industrial emissions must fall to 9 GtCeq by 2050 equal to the level in 2000 However the average literature sensitivity estimate suggests the level must be less than 2 GtCeq and in the high sensitivity case the target is simply unreachable unless we allow for overshoot Our results suggest that in light of the uncertainty in our knowledge of the climate sensitivity a longterm temperature target such as the 20°C target proposed by the European Commission can provide limited guidance to nearterm mitigation requirements
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