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The relationship between long-term climate goals and short/medium-term emission targets forms crucial information for the design of international climate policy. Since IPCC's 4th Assessment Report (AR4), a large number of new scenario studies have been published. This paper reviews this new literature and finds that there is more flexibility in the timing of short-term emission reductions compared to the earlier scenarios assessed by the AR4. For instance, the current literature suggests that a peak of emissions in 2020 and even 2030 would be consistent with limiting temperature change to about 2°C in the long term. The timing when emissions peak depends on whether negative emissions in the long-term can be achieved. The recent scenarios further indicate that global emissions by 2050 should be 40-80% below 2000 levels. Above all, the paper argues that there is no clear, single 'law' that would directly determine the required emissions levels in 2020, but that instead policy-makers need to consider trade-offs between the likelihood of achieving long-term targets, the short-term costs, and their expectation with respect to future technologies (and their possible failure). The higher flexibility might be important in finding acceptable agreements on international climate policy. [ABSTRACT FROM AUTHOR]

Preparatory talks to the next round of negotiations seem to indicate that a comprehensive agreement to mitigate climate change will not be easily attainable, despite the intentions of the US administration and the high expectations surrounding the Copenhagen meeting. One key reason is to what extent fast growing economies, and especially China, should take actions to reduce their growth of emissions. This paper argues that a turning point for international negotiations on climate change could be achieved if China were to agree on carbon obligations in the future. Results from modelling work suggest that the optimal investment behaviour is to anticipate the implementation of a climate policy by roughly 10 years, and that thus future commitments—if credible—could lead to significantly earlier steps towards carbon mitigation. If fast growing economies, and foremost China, believe in the long term objective of global stabilization of carbon concentrations, it might be economically rationale to sign on future targets, provided developed countries take on immediate action. Such a provision could be beneficial for both the developing and developed world. [ABSTRACT FROM AUTHOR]