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Turn Down The Heat: Why a 4C Warmer World Must Be Avoided
 

Turn Down The Heat: Why a 4C Warmer World Must Be Avoided

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Bill Hare, CEO of Climate Analytics, summarises the World Bank report Turn Down The Heat: Why a 4C Warmer World Must Be Avoided for The Climate Institute's Boardroom Lunch Conversation on 21 October ...

Bill Hare, CEO of Climate Analytics, summarises the World Bank report Turn Down The Heat: Why a 4C Warmer World Must Be Avoided for The Climate Institute's Boardroom Lunch Conversation on 21 October 2013.

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  • Schellnhuber et al., 2012 „Turn Down the Heat: Why a 4°C Warmer World Must be Avoided “, A Report for the World Bank by the Potsdam Institute for Climate Impact Research and Climate Analytics, 119 ppThis report provides a snapshot of recent scientific literature and new analyses of likely impacts and risks that would be associated with a 4° Celsius warming within this century. It is a rigorous attempt to outline a range of risks, focusing on developing countries and especially the poor. A 4°C world would be one of unprecedented heat waves, severe drought, and major floods in many regions, with serious impacts on ecosystems and associated services. But with action, a 4°C world can be avoided and we can likely hold warming below 2°C.
  • Schellnhuber et al., 2012 „Turn Down the Heat: Why a 4°C Warmer World Must be Avoided “, A Report for the World Bank by the Potsdam Institute for Climate Impact Research and Climate Analytics, 119 ppThis report provides a snapshot of recent scientific literature and new analyses of likely impacts and risks that would be associated with a 4° Celsius warming within this century. It is a rigorous attempt to outline a range of risks, focusing on developing countries and especially the poor. A 4°C world would be one of unprecedented heat waves, severe drought, and major floods in many regions, with serious impacts on ecosystems and associated services. But with action, a 4°C world can be avoided and we can likely hold warming below 2°C.
  • Whentheobserveddataareadjustedtoremovetheestimatedimpactofknownfactorson short-term temperaturevariations (ElNiño/southern oscillation, volcanicaerosolsand solar variability), the global warmingsignalbecomesevenmore evident asnoiseisreduced.IPCC projectionsare in linewiththeadjustedtemperaturesobservations.Comparingclimateprojectionstoobservationsupto 2011Environ. Res. Lett. 7 (2012) 044035 (5pp)Stefan Rahmstorf, Grant Foster and Anny Cazenavehttp://iopscience.iop.org/1748-9326/7/4/044035/pdf/1748-9326_7_4_044035.pdfAbstractWeanalyse global temperatureandsea-level dataforthepastfewdecadesandcomparethemtoprojectionspublished in thethirdandfourthassessmentreportsoftheIntergovernmental Panel on Climate Change (IPCC). The resultsshowthat global temperaturecontinuestoincrease in goodagreementwiththebestestimatesofthe IPCC, especiallyifweaccountfortheeffectsofshort-term variability due totheElNi˜no/Southern Oscillation, volcanicactivityand solar variability. The rate ofsea-level riseofthepastfewdecades, on theotherhand, isgreaterthanprojectedbythe IPCC models. This suggeststhat IPCC sea-level projectionsforthefuturemay also bebiasedlow.Figurecaptions:Fig.1:Sealevelmeasuredbysatellitealtimeter (redwith linear trendline; AVISO datafrom (Centre National d’EtudesSpatiales) andreconstructedfromtidegauges (orange, monthlydatafrom Church and White (2011)). Tide gaugedatawerealignedtogivethe same meanduring 1993–2010 asthealtimeterdata. The scenariosofthe IPCC areagainshown in blue (thirdassessment) andgreen (fourthassessment); theformerhavebeenpublishedstarting in theyear 1990 andthelatterfrom 2000.Fig.2:Figure 3. Rate ofsea-level rise in pastandfuture. Orange line, based on monthlytidegaugedatafrom Church and White (2011). The redsymbolwitherrorbarsshowsthesatellitealtimetertrendof 3.2 ± 0.5 mm yr−1 during 1993–2011; thisperiodistooshorttodeterminemeaningfulchanges in the rate ofrise. Blue/greenlinegroupsshowthelow, midand high projectionsofthe IPCC fourthassessmentreport, eachforsixemissionsscenarios. Curvesaresmoothedwith a singularspectrumfilter (ssatrend; Moore et al 2005) of 10 years half-width.
  • FifthAssessment Report (2013):likely in the range 1.5°C to 4.5°C (high confidence)extremely unlikely less than 1°C (high confidence)very unlikely greater than 6°C (medium confidence)
  • FifthAssessment Report (2013):likely in the range 1.5°C to 4.5°C (high confidence)extremely unlikely less than 1°C (high confidence)very unlikely greater than 6°C (medium confidence)
  • Global surface temperature change for the end of the 21st century is likely to exceed 1.5°C relative to 1850 to 1900 for all RCP scenarios except RCP2.6. Warming will continue beyond 2100 under all RCP scenarios except RCP2.6Unlikely to exceed 2°C for RCP2.6 (medium confidence). Warming as likely as not to exceed 4°C for highest of new IPCC scenarios (RCP8.5) (medium confidence). {12.4} by 2080-2100 averageSince rate of warming by that time is over 0.5°C/decade and percentage probability for >4°C is already 62% for 2081-2100 obviously by 2100 exceeding 4°C is likely and grows to very likely past 2100 ...For emissions-driven runs uncertainty range of warming is bigger and median warming higher due to C-cycle feedbacks (2.6-4.7°C for concentration-driven and 2.5-5.6°C for emissions-driven runs 2081-2100 above 1986-2005).
  • Global mean sea level will continue to rise during the 21st centuryUnder all RCP scenarios the rate of sea level rise will very likely exceed that observed during 1971–2010 due to increased ocean warming and increased loss of mass from glaciers and ice sheetsFor RCP8.5 the rise by the year 2100 is 0.52 to 0.98mRate of rise during 2081–2100 of 8 to 16 mm/yrFor RCP2.6sea level rise for 2081−2100 likely in the range of 0.26 to 0.55mRelative to 1986–2005
  • Uncertainty still considerableFor highest scenario RCP8.5 sea-level rise is 0.5-1 m by 2100High end of uncertainty is hard to establish:“… it has been concluded that there is currently insufficient evidence to evaluate the probability of specific levels above the assessed likely range” (IPCC AR5 WG1 SPM)Observations show that Antarctica mass loss is accelerating, equivalent to 0.1 mm/yr of SLR over 1992-2001, to 0.4 mm/yr over 2002-2011. However, AR5 projections assume zero contribution from AntarcticaA “… collapse of marine-based sectors of the Antarctic ice sheet, if initiated, could cause global mean sea level to rise substantially above the likely range … this additional contribution would not exceed several tenths of a meter of sea level rise during the 21st century” (IPCC AR5 WG1 SPM)
  • Rahmstorf et al (2012) “Comparing climate projections to observations up to 2011”, Environ. Res. Lett. 7 (2012) 044035 (5pp)Figure 2. Sea level measured by satellite altimeter (red with lineartrend line; AVISO data from (Centre National d’EtudesSpatiales)and reconstructed from tide gauges (orange, monthly data fromChurch and White (2011)). Tide gauge data were aligned to give thesame mean during 1993–2010 as the altimeter data. The scenariosof the IPCC are again shown in blue (third assessment) and green(fourth assessment); the former have been published starting in theyear 1990 and the latter from 2000.Abstract We analyse global temperature and sea-level data for the past few decades and compare themto projections published in the third and fourth assessment reports of the IntergovernmentalPanel on Climate Change (IPCC). The results show that global temperature continues toincrease in good agreement with the best estimates of the IPCC, especially if we account forthe effects of short-term variability due to the El Ni˜no/Southern Oscillation, volcanic activityand solar variability. The rate of sea-level rise of the past few decades, on the other hand, isgreater than projected by the IPCC models. This suggests that IPCC sea-level projections forthe future may also be biased low.
  • Schellnhuber et al., 2012 „Turn Down the Heat: Why a 4°C Warmer World Must be Avoided “, A Report for the World Bank by the Potsdam Institute for Climate Impact Research and Climate Analytics, 119 ppThis report provides a snapshot of recent scientific literature and new analyses of likely impacts and risks that would be associated with a 4° Celsius warming within this century. It is a rigorous attempt to outline a range of risks, focusing on developing countries and especially the poor. A 4°C world would be one of unprecedented heat waves, severe drought, and major floods in many regions, with serious impacts on ecosystems and associated services. But with action, a 4°C world can be avoided and we can likely hold warming below 2°C.
  • Schellnhuber et al., 2012 „Turn Down the Heat: Why a 4°C Warmer World Must be Avoided “, A Report for the World Bank by the Potsdam Institute for Climate Impact Research and Climate Analytics, 119 ppThis report provides a snapshot of recent scientific literature and new analyses of likely impacts and risks that would be associated with a 4° Celsius warming within this century. It is a rigorous attempt to outline a range of risks, focusing on developing countries and especially the poor. A 4°C world would be one of unprecedented heat waves, severe drought, and major floods in many regions, with serious impacts on ecosystems and associated services. But with action, a 4°C world can be avoided and we can likely hold warming below 2°C.
  • Schellnhuber et al., 2012 „Turn Down the Heat: Why a 4°C Warmer World Must be Avoided “, A Report for the World Bank by the Potsdam Institute for Climate Impact Research and Climate Analytics, 119 ppThis report provides a snapshot of recent scientific literature and new analyses of likely impacts and risks that would be associated with a 4° Celsius warming within this century. It is a rigorous attempt to outline a range of risks, focusing on developing countries and especially the poor. A 4°C world would be one of unprecedented heat waves, severe drought, and major floods in many regions, with serious impacts on ecosystems and associated services. But with action, a 4°C world can be avoided and we can likely hold warming below 2°C.
  • Nelson, G. C., Rosegrant, M. W., Koo, J., Robertson, R., Sulser, T., Zhu, T., … Lee, D. (2010). The Costs of Agricultural Adaptation to Climate Change.Objective showing that 8.5% decrease in total production will have detrimental consequences for per capita calories availabilityFor per capita availability, population projections used for the calculation are below UN projections (1.7 against 1.9).Per capita availability decreases steeply due to a global decrease in food production by the 2050s when global temperature is 2 degrees above pre-industrial levelIf African population was to remain constant between 2010 and 2050, per capita kcal availability would be between 2 and 3 times higher
  • Awp Assets wealth householdsAbp  Assets bottom (poor) householdsHouseholds driven into poverty traps do not have the capacity to cope and recover Carter, M. R., Little, P. D., Mogues, T., & Negatu, W. (2007). Poverty Traps and Natural Disasters in Ethiopia and Honduras. World Development, 35(5), 835–856. doi:10.1016/j.worlddev.2006.09.010Hallegatte, S., & Przyluski, V. (2010). The Economics of Natural Disasters Concepts and Methods. Washington, DC.
  • Schellnhuber et al., 2012 „Turn Down the Heat: Why a 4°C Warmer World Must be Avoided “, A Report for the World Bank by the Potsdam Institute for Climate Impact Research and Climate Analytics, 119 ppThis report provides a snapshot of recent scientific literature and new analyses of likely impacts and risks that would be associated with a 4° Celsius warming within this century. It is a rigorous attempt to outline a range of risks, focusing on developing countries and especially the poor. A 4°C world would be one of unprecedented heat waves, severe drought, and major floods in many regions, with serious impacts on ecosystems and associated services. But with action, a 4°C world can be avoided and we can likely hold warming below 2°C.
  • Global mean surface warming above 2°C under RCP2.6 is unlikely (medium confidence). Global mean surface warming above 4°C by 2081–2100 is unlikely in all RCPs (high confidence) except for RCP8.5 where it is as likely as not (medium confidence). Global warming reaches 0.6°C [0.0 to 1.2°C] under the RCP2.6 extension where sustained negative emissions lead to a further decrease in radiative forcing, reaching values below present-day radiative forcing by 2300. See  For RCP2.6, the models project an average 50% (range 14– 96%) emission reduction by 2050 relative to 1990 levels. It is about as likely as not that sustained globally negative emissions will be required to achieve the reductions in atmospheric CO2 in RCP2.6 

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