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A Stern Review of the Stern Review. Richard S.J. Tol Economic and Social Research Institute Hamburg, Vrije and Carnegie Mellon Universities. Agreement. Climate change is real and caused by humans Climate change is a problem Economics can shed light on climate policy - PowerPoint PPT Presentation
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A Stern Review ofthe Stern Review
Richard S.J. TolEconomic and Social Research
InstituteHamburg, Vrije and Carnegie
Mellon Universities
Agreement• Climate change is real and caused by
humans• Climate change is a problem• Economics can shed light on climate policy• Greenhouse gas emission reduction should
start now• Greenhouse gas emission reduction is best
implement with market-based instruments
• Stern is commended for putting this on the public and political agenda
Disagreement• Estimates of the costs of climate change• Estimates of the costs of emission
reduction• Optimal targets for emission reduction
• Stern is right for the wrong reasons – is this the best way of starting a public debate on the economics of climate policy?
Consensus• Being alone does not make you wrong,
but it should make you think – David Pearce
• Stern has been praised by the admirably fast readers Solow, Mirrlees, Sen, Stiglitz
• Stern has been criticised by Connelly, Helm, Hulme, Maddison, Mendelsohn, Nordhaus, Yohe, and by Dasgupta, Henderson, Varian, Weitzman
• Stern’s response to the criticism has been particularly vague
The Stern Review• The Stern Review was commissioned by
Gordon Brown and Tony Blair, perhaps in response to the critique of the House of Lords on the lack of economic analysis on UK climate policy
• There are 23 authors on the Stern Review, 50 or more consultants supported the review, and numerous experts attended workshops
• About 15 months of preparation• 575 pages, 36 background papers• Costs in excess of £2 million (estimate,
no information on Treasury website)
The Stern Review -2• The Stern Review is badly documented,
impossible to reproduce• Some of this was repaired later, including
several postscripts that undermine the headline conclusions and occasionally add more confusion
• One peer has admitted to having reviewed the Stern Review, and noted that his comments were not taken on board
• The Stern Review was circulated among the press before shown to experts on the economics of climate change
• Doesn’t HM Treasury have quality-control?
The Stern Review -3• The Stern Review is a literature survey –
there are no new data, no new models, no new analysis
• Yet, the Stern Review is completely out of step with the literature – and does not even alert the reader to this
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dollar per tonne of carbon
Is the Stern Review an outlier?
A Reconstruction• Three regions: poor, middle, rich• Income convergence• Population grows from 6 to 9 billion• Warming (2100) 2.3 / 3.1 / 4.5 K
with probability 0.15 / 0.70 / 0.15• Impact 5.6 / 3.3 / 1.0 %GDP for 3K
warming for poor / middle / rich• Impact quadratic in temperature• Very similar to PAGE2002 / SRES
A2
Welfare measures• Certainty- and equity-equivalent annuity
• CEEA calibrated to 5.3%• BGE dominated by scenario, BGE = -179.4%• The postscript to the postscript to the Stern
Review says they compute ΔBGE • ΔBGE = CEEA iff log util, implies scenario
independence
2200
,, , 2000
2200
, , ,, , , , 2000
ln (1 ) (1 )
ln (1 ) (1 )
ti t
i p m r t
tj i t i t j
j l mh i p m r t
y
y
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0.01 0.1 1 3
PRTP (%/ yr)
CEEA
(%
GD
P)
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CRRA (-)
CEEA
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P)
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I nequity aversion (-)
CEEA
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GD
P)
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2050 2100 2200 2300 2400 2500 3000 5000 12000
Horizon (yr)
CEEA
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Constant Falling
Vulnerability (% GDP/ 3K)
CEEA
(%
GD
P)
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957 750 700 650 600 550 500 450 400
Ambient CO2 in 2200 (ppmv)CEEA
(%
GD
P)
Summary• The Stern Review did not compute what
it said it did, and it used a particularly bad approximation
• A different set of ethical parameters – perhaps easier to defend, certainly more in line with the data – would have let to lower estimates
• Stern‘s benefit estimates were off by 30%
• Internally consistent scenario decreases estimates by 60%
Emission Reduction• Two papers support the Stern Review, but
the main report ignores Terry Barker‘s meta-analysis, and adopts Dennis Anderson‘s cost estimates instead
• Terry Barker gets the economics wrong, in subtle and complicated ways
• Dennis Anderson‘s work:– Stops at 2050– Suboptimal trajectory– No economic feedback– No capital stock turnover
Cost-Benefit Analysis• The Stern Review emphasizes the
uncertainties about climate change, but ignores those about emission reduction
• Inconsistent time horizons – recall that the impacts to 2050 are 1% of GDP, equal to the costs of abatement
• The Stern Review presents a cost-benefit analysis with two discrete alternatives:– Do nothing– Existing UK policy
• The range of policies is much wider
Cost-Benefit Analysis -2• Stern does a CBA with two alternatives:
– Do nothing– Existing UK policy
• Stern endorses the latter, even though his estimates of the costs of emission reduction are lower, and his estimates of the benefits are much higher than previous UK studies
• Stern resigned after UK climate policy did not change
• The EU has higher costs and lower benefits, but a stricter target
• I do not pretend to understand any of this
Conclusion• The Stern Review put the economics of
climate change on the public agenda• The Stern Review made a range of
procedural and technical errors• The Stern Review made peculiar ethical
assumptions• The quantitative results are fragile and
do not stand up to scrutiny, but the qualitative insights are robust – Stern was wrong but right
• HM Treasury hit a new low in quality• An economic case for emission
reduction now can be made – but the Stern Review missed the chance to make it
St Nicholas Rebuking the StormBicci di Lorenzo, 1433
Ashmolean Museum, Oxford