Editing Global warming potential (section)

== Other metrics to compare greenhouse gases ==

The ''Global Temperature change Potential'' (GTP) is another way to compare gases. While GWP estimates infrared thermal radiation absorbed, GTP estimates the resulting rise in average surface temperature of the world, over the next 20, 50 or 100 years, caused by a greenhouse gas, relative to the temperature rise which the same mass of {{CO2}} would cause.<ref name="ar5" /> Calculation of GTP requires modelling how the world, especially the oceans, will absorb heat.<ref name=":1" /> GTP is published in the same IPCC tables with GWP.<ref name="ar5" />

Another metric called GWP* (pronounced "GWP star"<ref name=Reply/>) has been proposed to take better account of short-lived climate pollutants (SLCPs) such as methane. A permanent increase in the rate of emission of an SLCP has a similar effect to that of a one-time emission of an amount of carbon dioxide, because both raise the radiative forcing permanently or (in the case of carbon dioxide) practically permanently (since the {{CO2}} stays in the air for a long time). GWP* therefore assigns an ''increase'' in emission rate of an SLCP a supposedly equivalent amount (tonnes) of {{CO2}}.<ref>{{cite journal |last1=Lynch |first1=John |last2=Cain |first2=Michelle |last3=Pierrehumbert |first3=Raymond |last4=Allen |first4=Myles |date=April 2020 |title=Demonstrating GWP*: a means of reporting warming-equivalent emissions that captures the contrasting impacts of short- and long-lived climate pollutants |journal=Environmental Research Letters |volume=15 |issue=4 |pages=044023 |bibcode=2020ERL....15d4023L |doi=10.1088/1748-9326/ab6d7e |pmc=7212016 |pmid=32395177}}</ref> However GWP* has been criticised both for its suitability as a metric and for inherent design features which can perpetuate injustices and inequity. Developing countries whose emissions of SLCPs are increasing are "penalized", while developed countries such as Australia or New Zealand which have steady emissions of SLCPs are not penalized in this way, though they may be penalized for their emissions of {{CO2}}.<ref>{{cite journal |last1=Meinshausen |first1=Malte |last2=Nicholls |first2=Zebedee |date=1 April 2022 |title=GWP*is a model, not a metric |journal=Environmental Research Letters |volume=17 |issue=4 |pages=041002 |bibcode=2022ERL....17d1002M |doi=10.1088/1748-9326/ac5930 |doi-access=free}}</ref><ref>{{cite journal |last1=Rogelj |first1=Joeri |last2=Schleussner |first2=Carl-Friedrich |date=1 November 2019 |title=Unintentional unfairness when applying new greenhouse gas emissions metrics at country level |journal=Environmental Research Letters |volume=14 |issue=11 |pages=114039 |bibcode=2019ERL....14k4039R |doi=10.1088/1748-9326/ab4928 |s2cid=250668916 |hdl-access=free |hdl=10044/1/77353}}</ref><ref name=Reply>{{cite journal |last1=Rogelj |first1=Joeri |last2=Schleussner |first2=Carl-Friedrich |date=1 June 2021 |title=Reply to Comment on 'Unintentional unfairness when applying new greenhouse gas emissions metrics at country level' |journal=Environmental Research Letters |volume=16 |issue=6 |pages=068002 |bibcode=2021ERL....16f8002R |doi=10.1088/1748-9326/ac02ec |doi-access=free}}</ref>