title: Setting cumulative emissions targets to reduce the risk of dangerous climate change.
abstract: Avoiding "dangerous anthropogenic interference with the climate system" requires stabilization of atmospheric greenhouse gas concentrations and substantial reductions in anthropogenic emissions. Here, we present an inverse approach to coupled climate-carbon cycle modeling, which allows us to estimate the probability that any given level of carbon dioxide (CO2) emissions will exceed specified long-term global mean temperature targets for "dangerous anthropogenic interference," taking into consideration uncertainties in climate sensitivity and the carbon cycle response to climate change. We show that to stabilize global mean temperature increase at 2 degrees C above preindustrial levels with a probability of at least 0.66, cumulative CO2 emissions from 2000 to 2500 must not exceed a median estimate of 590 petagrams of carbon (PgC) (range, 200 to 950 PgC). If the 2 degrees C temperature stabilization target is to be met with a probability of at least 0.9, median total allowable CO2 emissions are 170 PgC (range, -220 to 700 PgC). Furthermore, these estimates of cumulative CO2 emissions, compatible with a specified temperature stabilization target, are independent of the path taken to stabilization. Our analysis therefore supports an international policy framework aimed at avoiding dangerous anthropogenic interference formulated on the basis of total allowable greenhouse gas emissions.
authors.affiliation: School of Earth and Ocean Sciences, University of Victoria, Victoria, BC, Canada V8W3V6. kirsten.zickfeld@ec.gc.ca
authors.forename: Kirsten
authors.initials: K
authors.lastname: Zickfeld
authors.forename: Michael
authors.initials: M
authors.lastname: Eby
authors.forename: H Damon
authors.initials: HD
authors.lastname: Matthews
authors.forename: Andrew J
authors.initials: AJ
authors.lastname: Weaver
mesh_terms: D002245:Carbon Dioxide / Q000032:analysis* / Q000737:chemistry; D002980:Climate; D004463:Ecology / Q000379:methods / Q000639:trends; D004784:Environmental Monitoring / Q000379:methods*; D005544:Forecasting; D005740:Gases / Q000032:analysis / Q000737:chemistry; D017752:Greenhouse Effect; D018570:Risk Assessment; D012307:Risk Factors; D013696:Temperature
chemical_list: D005740:Gases; D002245:Carbon Dioxide
references.citation: Proc Natl Acad Sci U S A. 2007 Jun 12;104(24):9949-54
references.pmid: 17548822
references.citation: Proc Natl Acad Sci U S A. 2005 Nov 1;102(44):15728-35
references.pmid: 16150711
references.citation: Nature. 2002 Apr 18;416(6882):719-23
references.pmid: 11961550
references.citation: Nature. 2000 Nov 9;408(6809):184-7
references.pmid: 11089968
references.citation: Science. 2002 Jan 4;295(5552):113-7
references.pmid: 11778044
references.citation: Nature. 2009 Apr 30;458(7242):1158-62
references.pmid: 19407799
references.citation: Nature. 2004 Aug 12;430(7001):768-72
references.pmid: 15306806
references.citation: Proc Natl Acad Sci U S A. 2004 Nov 23;101(47):16411-6
references.pmid: 15545606
references.citation: Nature. 2009 Jun 11;459(7248):829-32
references.pmid: 19516338
references.citation: Nature. 2006 Apr 20;440(7087):1029-32
references.pmid: 16625192