IMF-缓解气候变化：到2050年实现净零排放的增长友好型政策（英）-2021.7-35正式版.ppt

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1、WPWP/2121/195Mitigating Climate Change:Growth-Friendly Policies toAchieve Net Zero Emissions by 2050by Florence Jaumotte,Weifeng Liu,and Warwick J.McKibbinIMFIMF Working PapersWorking Papers describedescribe research inresearch in progress byprogress by the author(s)and arethe author(s)and are publi

2、shedpublishedto elicit comments andto elicit comments and to to encourage debate.encourage debate.The views expressed in IMF Working Papersare those of the author(s)and do not necessarily represent the views of the IMF,itsExecutive Board,or IMF management.2021 International Monetary FundWP/21/195IMF

3、 Working PaperResearch DepartmentMitigating Climate Change:Growth-Friendly Policies to Achieve Net Zero Emissionsby 20501Prepared by Florence Jaumotte,Weifeng Liu,and Warwick J.McKibbinAuthorized for distribution by Oya CelasunJuly 2021IMF Working Papers describe research in progress by the author(s

4、)and are published toelicit comments and to encourage debate.The views expressed in IMF Working Papers arethose of the author(s)and do not necessarily represent the views of the IMF,its Executive Board,or IMF management.AbstractThe paper examines climate mitigation strategies to reach net-zero emiss

5、ions by mid-century,focusing on smoothing macroeconomic costs in the short-to medium-termthe horizonrelevant for policymakers.It explores a comprehensive policy package,which complementscarbon pricing with an initial green fiscal stimulus,consisting of green public investment andsubsidies to renewab

6、les production.Model simulations show that thanks to the green publicspending,the policy package boosts global output relative to the baseline for the first 15 yearsof the low-carbon transition.Subsequent transitional output costs resulting from furtherincreases in carbon prices are moderate of the

7、order of 1 percent of baseline global GDP by2050.The findings suggest that upfront green fiscal packages could help smooth the transitionto a low-carbon economy.In the current context of the Covid-19 economic crisis,they wouldhelp support the recovery from the crisis and put the global economy on a

8、greener,moresustainable path.JEL Classification Numbers:C51,C53,C54,C55,C68,F41,Q51,Q5Keywords:Climate Change,Net-Zero Emissions,Green Infrastructure,Macroeconomics,DSGE,CGE,G-CubedAuthors E-Mail Address:FJaumotteimf.org1 Background paper prepared for the October 2020 IMF World Economic Outlook.This

9、 paper provides a detailed presentation of thesimulation results from the October 2020 IMF World Economic Outlook chapter 3 and an additional scenario with carbon pricing only forcomparison with the comprehensive policy package where green investments were also included.This paper has greatly benefi

10、tted fromcontinuous discussions with Oya Celasun and Benjamin Carton on the design of simulations;contributions from Philip Barrett for part of thesimulations;and research support from Jaden Kim.We also received helpful comments from other IMF staff.All remaining errors are ours.McKibbin and Liu ack

11、nowledge financial support from the Australian Research Council Centre of Excellence in Population Ageing Research(CE170100005).TABLE OF CONTENTSI.Introduction.4II.Achieving Net-Zero Emissions by 2050.6III.Modeling Approach and Baseline Projections.8A.The Modeling Approach.8B.The Baseline Scenario.1

12、1IV.Net-Zero Emissions Scenario Design.13A.Net-Zero Emissions in 2050.13B.Policy Tools.14C.Cost-Benefit Analysis.16V.Results of Full Participation Scenarios.17A.Global Results.17B.Cross-Country Differences.22C.Policy Package vs.Carbon Tax Only.26VI.Results of Partial Participation Scenarios.29VII.Co

13、nclusion.31References.33FiguresFigure 1:Production Structure in the G-Cubed Model.10Figure 2:Baseline CO2 Emissions,GDP,and Energy Structure.13Figure 3:Global CO2 Emissions.18Figure 4:Global Real GDP.18Figure 5:Global Private Investment by Sector.19Figure 6:Global Employment by Sector.20Figure 7:Glo

14、bal Private Consumption.20Figure 8:Global Fiscal Impact.21Figure 9:Carbon Tax Rates by Region in the Policy Package.22Figure 10:Share of Low Carbon in Primary Energy by Region.23Figure 11:Regional Real GDP.23Figure 12:Co-Benefits by Region.24Figure 13:Private Investment by Region.25Figure 14:Private

15、 Consumption by Region.25Figure 15:Employment by Region.25Figure 16:Carbon Taxes by Region in the Carbon-Tax-Only Scenario.26Figure 17:GDP and Investment:Policy Packages vs.Carbon Tax Only.28Figure 18:Fiscal Impacts:Policy Package vs.Carbon Tax Only.29Figure 19:Partial Participation in Mitigation.30

16、TablesTable 1:Regions in the G-Cubed Model.8Table 2:Sectors in the G-Cubed Model.9Table 3:Global Carbon Removal Potentials in 2050(Gt CO2).14Table 4:Share of Total Productivity Gains from Public Invesment Allocated to Each Sector.16Table 5:CO2 Taxes by 2050 in the Policy Package and Carbon-Tax-Only

17、Scenarios.274I.INTRODUCTIONGlobal warming continues apace.The increase in the earths average temperature since theindustrial revolution is estimated at 1C and is believed to be accelerating.Each successivedecade since the 1980s has been warmer than the previous one,the past six years(20152020)were t

18、he warmest ever reported,and 2020 was the hottest year on record,tying 2016.Risingpressure on Earth systems is already evident from more frequent weather-related naturaldisasters.2 Global sea levels are rising,and evidence is mounting that the world is closer toabrupt and irreversible changesso-call

19、ed tipping pointsthan previously thought(Lentonand others 2019).The window to keep temperature increases to safe levels is rapidly closing.Scientists havewarned that temperature increases relative to preindustrial levels need to be kept well below2Cand ideally 1.5Cto avoid reaching climate tipping p

20、oints and imposing severe stresson natural and socioeconomic systems(IPCC 2014,2018a).The objective of limitingtemperature increases by 2100 to 1.52C was endorsed worldwide by policymakers in the2015 Paris Agreement.Sizable and rapid reductions in GHG emissions are needed for this goalto be met;spec

21、ifically,net GHG emissions need to decline to zero by mid-century(IPCC 2014,2018a).Achieving this goal means that GHG emissions must be eliminated or that anyremaining GHG emissions must be removed from the atmosphere by natural(for example,forests,oceans)or artificial(for example,carbon capture and

22、 storage)sinks.Even with suchdrastic reductions,temperatures may temporarily overshoot the target until the stock ofaccumulated GHG in the atmosphere is sufficiently reduced by absorption by carbon sinks.Tangible policy responses to reduce greenhouse gas emissions have been grossly insufficientto da

23、te.3 While the Covid-19 crisis has reduced emissions,it is already evident that this declinewill only be temporary.Under unchanged policies,emissions will continue to rise relentlessly,and global temperatures could increase by an additional 25C by the end of this century,reaching levels not seen in

24、millions of years,imposing growing physical and economicdamage,and increasing the risk of catastrophic outcomes across the planet.4A growing number of countries are announcing commitments to reach net-zero emissions bymid-century.To this day,58 countries accounting for 53.3%of global GHG emissions h

25、avecommunicated a net-zero target,including some of the largest emitters(the European Union,Japan,Korea,China,and the US).This paper focuses on reducing net carbon emissions to5zero by 2050 in each country/region.It examines how mitigation policies can be designed in agrowth-and employment-friendly

26、way.It considers a comprehensive policy package,complementing carbon pricing with upfront green supply policies,specifically green publicinvestment and subsidies to renewables production partly financed through debt financing.Theinitial green fiscal stimulus is key to supporting economic activity in

27、 the short run.As the2 See also Chapter 2 of the April 2020 Sub-Saharan Africa Regional Economic Outlook,Chapter 3 of the October 2017 World EconomicOutlook,and Kahn and others(2019).3 For most countries,the Nationally Determined Contributions pledged under the Paris Agreement are deemed insufficien

28、t to meet either the1.5C or the 2C target,and,judging by current policies,unlikely to be met in the first place(see Climate Action Tracker Warming ProjectionsGlobal UpdateDecember 2019).Views about the shortfalls of stated polices have been echoed by others,such as the International EnergyAgency,whi

29、ch points out that significantly more ambitious policies are needed to reach the targets(IEA 2019).4 Absent climate change mitigation policies or massive migration,one-third of the global population could experience mean annualtemperatures above 29C by 2070.Such temperatures are currently found in o

30、nly 0.8 percent of Earths land surface,mostly in Africa,andare projected to cover 19 percent of land by 2070(Xu and others 2020).The economic costs of rising climate risks are explored in Fernandoet al(2021).5 Net-zero Target Status|Explore Net-Zero Targets|Climate Watch Data5economy embarks on its

31、transition to a low-carbon path,it allows to offset the carbon taxsfinancial costs.In addition to the initial lift to aggregate demand,it boosts productivity in low-carbon sectors,increasing profitability and triggering more significant private investment inthese sectors.This policy also creates mor

32、e employment in low-carbon sectors,supporting theemployment transition out of high-carbon sectors.Finally,reducing emissions through a rangeof alternative approaches reduces the needed level of the carbon price and,hence,associatedtransitional economic costs.Such a policy aims to smooth the macroeco

33、nomic output costs in the short to medium termthe horizon most relevant to policymakersand at easing the response to carbon taxation byputting in place key infrastructure and scaling up low-carbon sectors(thereby reducingadjustment costs).The comprehensive policy package is compared with a scenario

34、that reliesentirely on carbon pricing,highlighting the latters less favorable output and employmentoutcomes.In the current economic recession related to the Covid-19 crisis,many have pointedout that the fiscal stimuli implemented in the recovery phase could be an opportunity.Theycan support the reco

35、very from the economic crisis and put the global economy on a greenerand more sustainable path by boosting green and resilient infrastructure investment.6Simultaneously,the results highlight that carbon pricing is a critical element of a policypackage to net-zero emissions.Green supply policies(of p

36、lausible magnitude)are in and ofthemselves unlikely to be sufficient to curb emissions to net-zero.While both green supplypolicies and carbon pricing increase the relative price of high-to low-carbon activities,onekey channel through which carbon pricing is more effective at curbing emissions is rai

37、sing thecost of energy and incentivizing energy efficiency.Contrary to most of the literature,we assume that each country/region sets an independentcarbon price designed to reduce emissions to net-zero by 2050,after considering the emissionsreduction effect of the green fiscal stimulus.Having countr

38、y-specific carbon prices isconsistent with the lack of appetite for global coordination on carbon pricing.The onlyexception is a group of selected oil-exporting and other economies where policies only targetto keep emissions at current levels;indeed,the economic activity in this group is alreadysign

39、ificantly affected by other regions mitigation efforts.Policy simulations are implemented using the G-Cubed global macroeconomic model(McKibbin and Wilcoxen 1999,2013;Liu and others 2020).The model features tencountries/regions,detailed energy sectors,forward-looking agents,real and nominal rigiditi

40、es,and fiscal and monetary policies.Because it has many short-term Keynesian features,it is wellsuited to examine the effects of mitigation policies on the macroeconomic dynamics in theshort and medium term,in addition to looking at long-term effects.The model focuses oncarbon emissions from fossil

41、fuel consumption,which is the primary driver of human-madegreenhouse gas emissions(IPCC 2014,2018a).Other sources of greenhouse gas emissionsbeyond domestic fossil fuel CO2 emissions(forestry,agriculture,methane leaks,industrialprocess emissions,F-gases,international aviation/maritime emissions)are

42、not covered.Other policy options,such as the further development and adoption of negative emissiontechnologies(e.g.,carbon capture and storage),are assumed to contribute to reaching net-zero6 For discussions on this,see Batini and others(2020),Black and Parry(2020),Hepburn and others(2020),and Bhatt

43、acharya and Rydge(2020).6emissions by offsetting some of the remaining emissions in 2050.However,they are notexplicitly modeled in the paper.The findings of the paper can be summarized as follows.First,an initial green investment pushcombined with initially moderate and gradually rising carbon price

44、s can deliver the neededemission reductions at reasonable output effects.The policy package has a net positive impacton global output for the initial 15 years,raising output on average by about 0.7 percent ofbaseline global GDP each year.After 15 years,the drag from the carbon tax is more significan

45、t,resulting in small net output losses of about 1 percent of baseline GDP by 2050.The estimatedtransitional GDP costs in this paper are within the range of other studies(0.56.5 percent ofGDP by 2050),albeit on the lower side of estimates.The lower costs reflect the support toeconomic activity from g

46、reen infrastructure investment and higher substitutability betweenhigh-and low-carbon energy in G-Cubed than in engineering-based models(see Chapter 6 ofIPCC 2014).These are moderate output losses in the context of the expected 120 percentcumulative global GDP growth over the next 30 years and the a

47、voidance of severe damagesfrom climate change in the second half of the century.Second,preannounced and graduallyrising carbon prices are an essential policy to deliver the quick and substantial reductions incarbon emissions required to reach net-zero emissions by 2050.Most of the emissionsreduction

48、s are driven by the carbon tax,reflecting its strong incentivizing of energy efficiency.Third,the economic costs of the low-carbon transition differ across the world.Countries withfast economic and population growth(such as India,and to a lesser extent China),those withheavy reliance on high-carbon

49、energy(such as China),and most oil producers bear moresignificant transition costs.However,for fast-growing countries,these costs remain smallgiven the projected growth of these economies over the next 30 years(even under mitigation).These costs also need to be weighed against substantial avoided da

50、mage from climate changeand co-benefits from climate change mitigation,such as reduced local pollution and mortalityrates.For fossil fuel producers,the required diversification of their economies will be difficult,but many of them also stand to benefit from global climate change mitigation.Last but