Some of the slow climate change response to increasing greenhouse gas concentrations can be prevented by reducing greenhouse gas concentrations after a peak is reached. Such so-called ‘peaking scenarios’ can have a 10-20% greater probability of meeting climate targets (e.g. restricting the rise in temperature to a maximum of 2 degree) or have the same probability of achieving the climate targets at up to 40% lower costs. Peaking profiles can be especially important for making ambitious climate targets achievable.
Peaking profiles can achieve global temperature targets with more likelihood at lower costs
In long-term climate strategies to date both policy and research have focused particularly on the question how to stabilise the greenhouse gas concentrations in the atmosphere and on the climate effects associated with this stabilisation. Den Elzen and Van Vuuren demonstrate what cost and environmental benefits can be realised by focusing on long-term climate strategies based on so-called concentration peaking scenarios.
The reason these peaking scenarios are so advantageous is that – as the climate response always lacks behind the concentrations – a substantial part of the temperature rise still has to occur at the moment of stabilisation. This article shows that it is possible to prevent some of the slow part of the temperature rise by forcing the concentrations further into decline after stabilisation. In this way an increase in the probability of meeting climate targets can be reached at almost the same cost. Similarly, the same ambitious climate targets can be achieved with a slightly retarded peaking scenario at lower costs than in a stabilisation scenario. Both of these alternative strategies can play an essential role in achieving ambitious climate targets. On the basis of these results more attention in science and policy discussions should be paid to ‘peaking’ and ‘peaking level’ of concentrations than to ‘stabilising’ and ‘stabilisation level.’
It should be noted, however, that these advantages are only attainable in situations where the concentration peaks are confined. The advantages mentioned will disappear if the ‘overshoot’ in targeted concentrations is too high – or more crucially – if the overshoot lasts too long.
The article is an open access article and can be downloaded free of charge at the PNAS site