History of the 2^°C climate target

Abstract

Policymakers, scientists, and social scientists have debated a wide array of responses to the realities and prospects of anthropogenic climate change. The focus of this review is on the 2 • C temperature target, described as the maximum allowable warming to avoid dangerous anthropogenic interference in the climate. The temperature target has its roots in the ways in which scientists and economists developed heuristics from the 1970s to guide understanding and policy decision making about climate change. It draws from integrated assessment modeling, the 'traffic light' system of managing climate risks and a policy response guided as much by considerations of tolerability of different degrees of climate change as by simply reducing carbon dioxide emissions. The European Union (EU) proposed 2 • C as the policy target in 1996, with support from some environmentalists and scientists. It was subsequently listed as the desirable temperature target in the 2009 Copenhagen Accord. Yet the figure has a range of critics from scientific experts to economists arguing that the target is infeasible, expensive, and an inappropriate way of framing climate policy. Tracing the historical development of the target helps understand the context it emerged from and its various strengths and weaknesses.

Switch: A Planning Tool for Power Systems with Large Shares of Intermittent Renewable Energy

“…This ensures that the costs calculated for operation of the power system are based on the resources that are typically available in each hour, not the maximum that could be available if every piece of equipment worked correctly. 1 This de-rated capacity is similar to the "unforced capacity" used for generating plants in the NYISO and PJM capacity auctions (4).…”

“…Little information is available on the cost of providing this service, but this value is in the range suggested by several sources: (1) E3 ( Ofgem (UK) (35) reports that distribution costs make up 25-30 percent of British power bills. If they make up a similar proportion of California power bills, and California has a load factor of 0.6 and average power costs of $0.12/kWh, then this would mean that a customer with a 1 kW peak load would incur 0.6 kWa/kWp × 8760 hours/year × $0.12/kWah × 0.25 = $160/kWp/year in distribution costs.…”

“…1 The best estimate is that this will require limiting cumulative CO 2 emissions to about 10 12 tonnes of carbon before fossil fuels are completely phased out. 2 However, it is possible that the safe emissions budget is as low as half this levelapproximately the amount we have already emitted.…”

The level of climate-change mitigation depends on how humans assess the risk arising from missing the 2°C target

“…T he 2°C climate target stipulates that globally averaged surface warming should be limited to less than 2°C above pre-industrial levels (Rijsberman and Swart, 1990;WBGU, 1995;Ott et al, 2004;Tol, 2007;Ramanathan and Feng, 2008;Randalls, 2010;Cointe et al, 2011;Jaeger and Jaeger, 2011;Moellendorf, 2011). The 2°C target has emerged as the most prominent candidate (Randalls, 2010;Cointe et al, 2011;Jaeger and Jaeger, 2011) for fulfilling the mandate by the United Nations Framework Convention on Climate Change (UNFCCC) to "prevent dangerous anthropogenic interference with the climate system" (UNFCCC, 1992).…”

“…The 2°C target has emerged as the most prominent candidate (Randalls, 2010;Cointe et al, 2011;Jaeger and Jaeger, 2011) for fulfilling the mandate by the United Nations Framework Convention on Climate Change (UNFCCC) to "prevent dangerous anthropogenic interference with the climate system" (UNFCCC, 1992). However, meeting a temperature target alone cannot comprehensively avoid dangerous interference (Steinacher et al, 2013;IPCC, 2014); furthermore, some fundamental critique of the 2°C target has been levied (Shaw, 2010;.…”