Impact of Current Climate Proposals
| Published date | 01 February 2016 |
| Date | 01 February 2016 |
| DOI | http://doi.org/10.1111/1758-5899.12295 |
| Author | Bjorn Lomborg |
Impact of Current Climate Proposals
Bjorn Lomborg
Copenhagen Consensus Center
Abstract
This article investigates the temperature reduction impact of major climate policy proposals implemented by 2030, using the
standard MAGICC climate model. Even optimistically assuming that promised emission cuts are maintained throughout the
century, the impacts are generally small. The impact of the US Clean Power Plan (USCPP) is a reduction in temperature rise by
0.013°C by 2100. The full US promise for the COP21 climate conference in Paris, its so-called Intended Nationally Determined
Contribution (INDC) will reduce temperature rise by 0.031°C. The EU 20-20 policy has an impact of 0.026°C, the EU INDC
0.053°C, and China INDC 0.048°C. All climate policies by the US, China, the EU and the rest of the world, implemented from
the early 2000s to 2030 and sustained through the century will likely reduce global temperature rise about 0.17°C in 2100.
These impact estimates are robust to different calibrations of climate sensitivity, carbon cycling and different climate scenarios.
Current climate policy promises will do little to stabilize the climate and their impact will be undetectable for many decades.
The goal of any climate policy is to reduce the very real
problem of global warming. Mitigation policies focus mostly
on reducing greenhouse gas emissions, thereby reducing cli-
mate change. The most prominent indicator of climate
change is temperature rise. Here I define impact of a mitiga-
tion climate policy as its reduction in temperature rise.
To evaluate a mitigation climate policy it is crucial to know
the impact of this policy. The classic article to assess a mitiga-
tion policy is Wigley (1998), which estimated the impact of
the Kyoto Protocol on temperature rise and sea level rise.
However, a Web of Science search does not indicate any
numerical impact reviews of later significant policy proposals.
1
Thus, this article will produce an update of Wigley (1998) for
the most important new climate policies, including the
Intended Nationally Determined Contributions (INDCs) sub-
mitted in advance of the Paris COP21 negotiations.
Methodology
The current paper will use the same basic methodology as
Wigley (1998). First, Wigley identifies the policy to be analyzed
(the Kyoto Protocol). Second, he identifies the baseline of
emissions –what would have happened had there been no
Kyoto Protocol. Third, he makes a number of extrapolations of
the Kyoto policy throughout the 21st century. Fourth, he runs
the baseline and the Kyoto emissions through a climate
model, evaluating the impact of the Kyoto climate policy in
terms of temperature rise reduction and sea level rise reduc-
tion. Fifth, he does a sensitivity analysis by running the scenar-
ios through more and less CO
2
-sensitive models.
When identifying the climate policies to be analyzed, we
can identify the most important in terms of CO
2
reduction
from the recent overview of the INDCs by Boyd, Turner and
Ward (2015). Here they find the reductions of the US, the EU
and China to constitute 75–81 per cent of all reductions in
2030. The updated analysis provided below finds a pretty sim-
ilar total reduction from the US, the EU and China, although
the US reductions are much lower and the EU reductions
much higher than found in Boyd, Turner and Ward (2015).
Finally, the analysis includes the totality of all the INDC pro-
mises, including the remaining 22 per cent from Canada,
South Korea, Russia, Japan etc.
There are a vast number of potential baselines. We need
both a global baseline and a policy-relevant baseline, e.g.
for the EU or China. For a global baseline, Wigley (1998)
uses the original Intergovernmental Panel on Climate
Change (IPCC) business-as-usual (BAU) scenario, IS92a. This
has since been superseded by two newer scenario collec-
tions, the Special Report on Emissions Scenarios (SRES) from
2000 and the Representative Concentration Pathways (RCP)
from 2011, neither of which have a simple BAU scenario.
Indeed, the RCP scenarios are predominantly climate science
focused, and do not have any consistent socioeconomic
design (van Vuuren et al., 2011). For the most recent IPCC
report, AR5, the literature holds about 250 BAU scenarios
(UNEP, 2014, p. 34). The choice of global BAU scenario
determines the absolute temperature. Since we are inter-
ested in the difference between a BAU scenario and the sim-
ilar BAU scenario with a policy emission reduction, the
global BAU scenario decision matters little. Here I use the
RCP8.5, which is regarded as a worst-case scenario.
Sensitivity analysis shows that the results change little when
using other scenarios like RCP6 and SRES A1B, which are
better-case outcomes. The median of the main AR5 BAU
scenarios used below lie right inbetween RCP8.5 and RPC6
(see supplementary information).
For the BAU scenarios for the US, the EU, and China, I use
the official baseline for the US Energy Information Agency
(EIA) (EIA, 2015a), and the median of the latest two big
socioeconomic studies of the EU (Energy Modeling Forum
28; Knopf et al., 2013) and of China (Asia Modeling Exercise
(Calvin et al., 2012)).
Global Policy (2016) 7:1 doi: 10.1111/1758-5899.12295 ©2015 The Authors. Global Policy published by Durham University and John Wiley & Sons Ltd.
This is an open access article under the terms of the Creative Commons Attribution-NonCommercial-NoDerivs License, whic h permits use and
distribution in any medium, provided the original work is properly cited, the use is non-commercial and no modifications or adaptations are made.
Global Policy Volume 7 . Issue 1 . February 2016 109
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