ovRi-YAcademyGeophysical19The 21st Conference of the Parties in Paris in December Various studies have been conducted regarding the 2.0C14CVautard et al., 2014; Sui et al., 2015; Jiang et al., 2016.Regional climates are the result of complex processes thatvary strongly with location and therefore respond differently* Corresponding author.E-mail address FU Y.-H..Peer review under responsibility of National Climate Center ChinaMeteorological Administration.Available online at ScienceDirectAdvances in Climate Changehttps//doi.org/10.1016/j.accre.2017.12.0012015 agreed to take steps towards limiting the global meanannual surface air temperature increase to well below 2C14Cabove pre-industrial levels, and to pursue efforts towards atarget of 1.5C14C. As of August 2017, 195 members of theUnited Nations Framework Convention on Climate Changesigned the Paris Agreement, and 160 of these members ratifiedit. Decision makers need reliable ination on the impactscaused by these warming levels for climate mitigation andadaptation measures. The Intergovernmental Panel on ClimateChange has accepted the invitation to generate a special reporton the impacts of global warming of 1.5C14C by 2018. As parttarget Joshi et al., 2011; Jiang and Fu, 2012; Zhang, 2012;Zhang et al., 2013; Vautard et al., 2014; Sui et al., 2015;Jiang et al., 2016. For instance, by analyzing the resultssimulated by Coupled Model Intercomparison Project Phase 3CMIP3 models, Jiang and Fu 2012 pointed out that the2.0C14C global warming is projected to occur in 2064, 2046 and2049 under the SRES B1, A1B and A2 in multi-modelensemble MME, respectively, but would occur in a 30e40-year period in the individual models. For the RepresentativeConcentration Pathways RCPs, the globally averaged tem-perature would cross the 2.0C14C threshold sometime between2030 and 2060 under RCP4.5 and RCP8.5 Zhang, 2012;1. Introduction of an ambitious and urgent plan, a wide-ranging analysis onthe effects of limiting global warming to 1.5C14C is required.This study investigated the projected changes in the annual mean surface air temperature SAT over China under the 1.5 and 2.0C14C targets,by analyzing the outputs from 22 models of the Coupled Model Intercomparison Project Phase 5. Under the 1.5C14C target, the scope of changesin the average SAT over China is quite narrow and has the largest probability to increase by 1.7e2.0C14C under the various RCP pathways,although the time of occurrence of the 1.5C14C target has a large spread of 40e60 years. Similarly, the models consistently show that the averageSAT over China would most likely increase by 2.4e2.7C14C under the 2.0C14C target. Furthermore, the warming shows a clear spatial distinctionover China being stronger in the northwest part and weaker in the southeast part. Under all RCP pathways, the SAT over the northwest partwould increase by 1.9e2.1C14C for the 1.5C14C target, which is much stronger than the SATincrease over the southeast part 1.3e1.5C14C. A similarspatial pattern appears for the 2.0C14C target.Keywords Temperature; Warming; 1.5C14C target; 2.0C14C target; ChinaChanges in surface air temperatureglobal warmingFU Yuan-Haia,*, LUaClimate Change Research Center, ChinesebNational Key Laboratory of Numerical Modeling for Atmospheric Sciences andof Sciences, BeijingReceived 27 September 2017; revised 16 NovAvailable onlineAbstract1674-9278/Copyright 2017, National Climate Center China Meteorological AThis is an open access article under the CC BY-NC-ND license http//creativecommons.orer China under the 1.5 and 2.0C14Ctargetsub, GUO Dongaof Sciences, Beijing 100029, ChinaFluid Dynamics, Institute of Atmospheric Physics, Chinese Academy100029, Chinaember 2017; accepted 13 December 2017December 2017Research 9 2018 Production and hosting by Elsevier B.V. on behalf of KeAi.g/licenses/by-nc-nd/4.0/.historical climate simulation HIST and future climate changeunder RCP2.6, RCP4.5, RCP6.0 and RCP8.5. Table 1 lists thedetailed features of the models, and additional details aredocumented at http//cmip-pi.llnl.gov/cmip5/index.htmlsubmenuheader0.For the models, 145-year historical simulations1861e2005 are used, and only one realization is chosen foreach model. The simulations for 2006e2100 under RCP2.6,RCP4.5, RCP6.0 and RCP8.5 in all models are used for futureglobal warming projections. The warming threshold in thisstudy is relative to the pre-industrial climate, and the years1861e1900 are used as the quasi-pre-industrial baseline tocalculate the years in which global warming would reach the113Change Research 9 2018 112e119to changes in global-scale influences. The CMIP3 MMEsuggested that the annual mean surface air temperature SATaveraged over China would be elevated by 2.7e2.9C14C whenthe 2.0C14C target occurred, but the scope of warming is quitelarge approximately 2.3e3.0C14C among the individualmodels Jiang and Fu, 2012. These authors also showed thatthe warming is stronger towards the north and on the Qinghai-Tibetan Plateau. Based on the simulations of the CoupledModel Intercomparison Project Phase 5 CMIP5 models, theMME showed that the annual mean SAT averaged over Chinawould increase by 2.6C14C under a 2.0C14C global warming Suiet al., 2015, and Northwest China shows the fastest warmingtrend and followed by Central North China and NortheastChina Zhang, 2012.Unlike the 2.0C14C target, the 1.5C14C target is relativelyunexplored, and there is a relative lack of scientific knowledgeabout the implications of 1.5C14C warming Hulme, 2016;Mitchell et al., 2016; Schleussner et al., 2016; Zhai et al.,2017; Zhang et al., 2017. The CMIP5 MMEs showed thatthe global mean 1.5C14C warmings related to the pre-industriallevel 1861e1900 would occur by approximately 2036, 2028,2033 and 2025 under RCP2.6, RCP4.5, RCP6.0 and RCP8.5,respectively Hu et al., 2017. At the moment, the meantemperature over Asia would increase by 2.3C14C, with strongerwarming in high latitudes than in low latitudes, and it wouldbe 0.5e1.0C14C lower than that under the 2.0C14C target Xuet al., 2017. A warming of 0.5C14C from 1.5C14Cto2C14Cwould lead to significant increases in the temperature andprecipitation extremes in most regions Wang et al., 2017.However, these studies have focused solely on global-scalerather than China. The possible changes over China related tothe pre-industrial level that are associated with the 1.5C14C targethave not yet been investigated in detail. Zhou et al. 2016ashowed widespread significant changes in temperature ex-tremes are consistent with warming in observations. In addi-tion, the surface warming over global dry lands is 20e40higher than over humid lands in the past century Huang et al.,2017. According to the differential warming over land andocean and dry- and wet-land, it is believed that the impacts of a0.5C14C warming mitigation over China deserve to be quanti-tatively assessed, which would provide a better insight into thebenefits of limiting from 2.0 to 1.5C14C to the regional stake-holders e.g., hydrologists, ecologists, resource planners.Thus, we will investigate the possible changes in the SAT overChina under the 1.5 and 2.0C14C targets to provide a regionalperspective under the global warming targets.The organization of this paper is as follows. In Section 2,the datasets and s used in this study are described. Thechanges in the SAT averaged over China under the 1.5 and2.0C14C targets are shown in Section 3. Section 4 shows thespatial characteristics of the changes. Section 5 providesconclusions and discussion.2. Data and sFU Y.-H. et al. / Advances in ClimateWe analyzed the results of 22 models in the World ClimateResearch Programmes CMIP5 multi-model archive for their1.5 and 2.0C14C targets under the various RCP pathways. Allsimulation data have been interpolated onto a common2.5C14C2 2.5C14grid to enable the MME analysis and the com-parison between the individual simulations. The MME is ob-tained by simply averaging the available models withequivalent weights.3. Changes in SATaveraged over China under the 1.5 and2.0C14C targetsFig. 1a shows the projected changes in the global meanannual SAT relative to the pre-industrial reference period1861e1900 in the MMEs. Generally, the 1.5C14C warmingtargets would occur in 2029 under RCP2.6, 2027 underRCP4.5, 2031 under RCP6.0 and 2025 under RCP8.5. Thetimes are almost the same as those in Hu et al. 2017 and Shiet al. 2018, except the target is hit approximately 7 yearsearlier than that in Hu et al. 2017 under RCP2.6. In addition,the globally averaged temperature would not exceed 2.0C14Cabove the pre-industrial level under RCP2.6. The globalwarming would pass the 2.0C14C threshold in 2048, 2054 and2039 under RCP4.5, RCP6.0 and RCP8.5, respectively.Unfortunately, there is a large diversity among the timeswhen the 1.5 and 2.0C14C thresholds are crossed in the indi-vidual models Fig. 2, which is consist with Shi et al. 2018.Under the low emission scenario RCP2.6, the 1.5C14C target isprojected to occur in 16 models approximately 73 at timesranging from 1998 to 2051, showing a spread of 54 yearsFig. 2a. Only eight models project the 2.0C14C target thatTable 1Descriptions of the models used in this study.Model I.D. Resolution Model I.D. ResolutionBCC-CSM1 128 C2 64 GISS-E2-R 144 C2 89BCC-CSM1-1-M 320 C2 160 HadGEM2-AO 192 C2 145CCSM4 288 C2 192 HadGEM2-ES 192 C2 145CESM1-CAM5 288 C2 192 IPSL-CM5A-LR 96 C2 96CSIRO-MK3.6 192 C2 96 IPSL-CM5A-MR 144 C2 143FGOALS-s2 128 C2 108 MIROC5 256 C2 128FIO-ESM 128 C2 64 MIROC-ESM 128 C2 64GFDL-CM3 144 C2 90 MIROC-ESM-CHEM 128 C2 64GFDL-ESM2G 144 C2 90 MRI-CGCM3 320 C2 160GFDL-ESM2M 144 C2 90 NorESM1-M 144 C2 96GISS-E2-H 144 C2 89 NorESM1-ME 144 C2 96Change114 FU Y.-H. et al. / Advances in Climatewould occur in a 73-year period 2014e2086. Under RCP4.5,the 1.5C14C target would occur in all models within a 52-yearperiod ranging from 1998 to 2049 Fig. 2b. At the sametime, the 2.0C14C target would occur within 72 years2013e2084 in 18 models. The RCP6.0 is also a mediumstabilization scenario that stabilizes the radiative forcing at6.0 W mC02in 2100 without ever exceeding that value vanVuuren et al., 2011. Under this pathway, the global warm-ing would reach 1.5C14C within a 63-year period from 1998 to2060, and cross 2.0C14C within a 70-year period from 2010 to2079 in all models Fig. 2c. Under the highest emissionscenario RCP8.5, the models show a relatively narrowerspread in the years when the 1.5 and 2.0C14C thresholds arecrossed than those under the other three pathways Fig. 2d.The global warming would exceed the 1.5C14C target in theyears ranging from 1998 to 2041, and cross the 2.0C14Cthreshold in the years from 2012 to 2055 for all models, bothwithin a 44-year period.Fig. 1. a The 31-year slipping changes in annual mean global SAT relativeto the pre-industrial baseline 1861e1900 under RCP2.6, RCP4.5, RCP6.0 andRCP8.5 in MME. b, same as in a, but for the annual mean SAT averagedover China Shading indicates the dispersion of one standard deviation fromMME result.Under the global 1.5C14C target, the average warming overChina would be approximately 1.8C14C relative to the pre-industrial level in the MMEs for all RCP pathwaysFig. 1b. Under the 2.0C14C target, the annual mean SAT overChina would increase by approximately 2.6C14C in the variouspathways. These results suggest that the warming over Chinais faster than the global mean, which is consistent with pre-vious studies Jiang and Fu, 2012; Hu et al., 2017; Shi et al.,2018.For both the 1.5 and 2.0C14C targets, the average warmingover China are quite concentrated among the individualmodels under the various pathways, although certain di-versity exists Fig. 2. Under RCP2.6, the average warmingsover China are projected to be within the range of1.5e2.0C14C under the 1.5C14C target in almost all models, nomatter when the targets are reached Fig. 2a. For the 2.0C14Ctarget, the average SAT would increase by 2.6e2.9C14Cinsixof the eight models that cross the 2.0C14C threshold. Underthe other three pathways, the SAT over China would in-crease by 1.5e2.2C14C in almost all models under the 1.5C14Ctarget, except for two models under RCP4.5 and RCP6.0and one model under RCP8.5 which do not project theglobal 1.5C14CwarmingFig. 2bed. Under the 2.0C14C target,the warmings would be within the range of 2.2e2.9C14Cin17, 18, and 20 of the models under RCP4.5, RCP6.0 andRCP8.5, respectively.We calculated the probability density function PDF of theprojected warming averaged over China under the 1.5 and2.0C14C targets to further quantitatively uate the warmingrates among the individual models Fig. 3. Under the 1.5C14Ctarget, the largest PDF values are approximately 2.0, 1.8, 1.7and 1.9C14C under RCP2.6, RCP4.5, RCP6.0 and RCP8.5,respectively Fig. 3a. The diversity is very small among thues. This result suggests that with a global 1.5C14C warming,the SAT averaged over China has the largest probability toincrease by 1.7e2.0C14C relative to the pre-industrial level. Theshapes of the PDF curves are very similar. The mean valuesare approximately 1.8C14C for all RCP pathways, and thestandard deviations StDs are approximately 0.2, 0.2, 0.3, and0.2C14C under RCP2.6, RCP4.5, RCP6.0 and RCP8.5, respec-tively Table 2. The concentrated mean values and StDsfurther certify the unanimous results among the variouspathways. The StDs are only approximately 11 of the meanvalues, indicating a very weak dispersion among the models.Under the 2.0C14C target, the largest PDF values areapproximately 2.7, 2.5, 2.4 and 2.6C14C under RCP2.6, RCP4.5,RCP6.0 and RCP8.5, respectively Fig. 3b. The warming ismost pronounced under RCP8.5, followed by RCP4.5 andRCP6.0, but with a difference of only approximately 0.1C14C.The models that evolved in the PDF calculations are themodels that are very sensitive to global warming, and thusresult in strong warming under RCP2.6 Fig. 2a. Therefore,the average warming over China is most likely increase by2.4e2.7C14C when global warming crosses the 2.0C14C threshold.In addition, the mean values are 2.6, 2.5, 2.5 and 2.6C14C, whichResearch 9 2018 112e119are very consistent with each other under the various path-ways, while the StDs are 0.3, 0.3, 0.3 and 0.2C14C under the fourFig. 2. Scatter diagram of the target times and the corresponding changes in theindividual models and MMEs under a RCP2.6, b RCP4.5, c RCP6.0 and dFig. 3. Probability density functions PDFs of the changes in the annual meanSAT averaged over China in individual models under RCP2.6, RCP4.5,RCP6.0 and RCP8.5 for the a 1.5 and b 2.0C14C targets.FU Y.-H. et al. / Advances in Climate Change1.01.52.02.53.03.51990 2010 2030 2050 2070 2090Temperature anomaly
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