Climate Policy Michael Springborn Department of Environmental Science & Policy [image: USGCRP, 2010]
Climate policy questions and lenses • How aggressively and in what way should society take action to reduce damages from climate change? • balance between expected impacts/costs and policy response options and their costs • Mitigation versus adaptation • Economics/policy science/ ethics/climate science • game theory, theories on the use of science in policy and analysis of public attitudes. • International/national/state
The problem in a nutshell [Trenberth 2009]
Higher GHG concentrations map to uncertain but substantial changes in temperature [Pizer 2007]
The paleoclimatic record suggests anticipated GHG concentrations are quite unusual [Dieter et al. 2008]
The paleoclimatic record suggests anticipated GHG concentrations are quite unusual [NAS, 2014]
Predicted outcomes are uncertain:the recent mismatch between increasing GHG concentrations and flat temperature is a puzzle “The world added roughly 100 billion tonnes of carbon to the atmosphere between 2000 and 2010. That is about a quarter of all the CO₂ put there by humanity since 1750.” James Hansen (NASA): “the five-year mean global temperature has been flat for a decade” [The Economist, 2013]
Projected US temperature changes are substantial even for optimistic emissions scenarios From… U.S. Global Change Research Program: National Climate Assessment and Development Advisory Committee Draft Climate Assessment Report (2013). Temperature is relative to the 1901-1960 average. (USGCRP 2013, p. 20) • A2 scenario: high population growth, low economic growth, slower technology improvements and diffusion, and other factors that contribute to high emissions and lower adaptive capacity • B1 scenario: lower population growth, higher economic development, a shift to low-emitting efficient energy technologies that are diffused rapidly around the world through free trade, and other conditions that reduce the rate and magnitude of changes in climate averages and extremes as well as increased capacity for adaptation.
Undesirable impacts are expected as temperature increases across a range of settings [IPPC 2007]
The intensity of CO2/GDP is falling…but not fast enough to offset increases in GDP and population [Nordhaus, 2012]
Anthropogenic climate change represents the “biggest market failure the world has ever seen” -- Nicholas Stern.
Market failure specifies the root of the problem “greatest good for the greatest number” results when the actions of an agent (individual or firm) have an uncompensated effect on the wellbeing of other agents. EPA (2010)
Climate change externalities • (External) cost (damage) from a unit of emissions associated with a given unit of economic activity is not paid for by those producing or consuming the good. • Emissions inefficiently high • Innovators of new technologies (of any kind which addresses the GHG problem) may not receive all of the benefits from their inventions • Innovation is ineffeciently low
Each externality associated with climate change motivates consideration of particular policy instruments. Stern, 2013
What is the social cost of carbon (SCC) and why are we calculating it? U.S. Interagency Working Group on the SCC: The SCC is “an estimate of the monetized damages associated with an incremental increase of carbon emissions in a given year” [US IWGSCC, 2010]
Integrated assessment models are used to construct and analyze forecasts of the coupled economic-climatic system over centuries [Nordhaus, 2012]
Various IAMs project different levels of loss from temperature increases (IWGSCC 2010)
Economists have generally arrived at a consensus on the bottom-line: • “Virtually every activity directly or indirectly involves combustion of fossil fuels, producing emissions of carbon dioxide into the atmosphere. • Single bottom line for policy: “correct this market failure by ensuring that: • all people, everywhere, and for the indefinite future are confronted with a market price for the use of carbon that reflects the social costs of their activities.” Nordhaus et al. (2008)
Setting stringency: The policy ramp vs. the big bang • Climate “policy ramp” • Efficient GHG control policy: “modest rates of emissions reductions in the near term, followed by sharp reductions in the medium and long term.” (Nordhaus, 2007) • If implemented via a tax: ~$30/ton of CO2 initially, rising gradually to $200/ton towards 2100 (Krugman, 2010) • The “big bang”** (**Paul Krugman’s term) • Immediate and aggressive GHG control • Stern Review (2006): high profile challenge to the ramp
Regardless of whether the policy involves a tax or cap and trade, policy stringency can be expressed in terms of a carbon price Stringency of the policy ramp vs. big bang Stern: big-bang Nordhaus: policy ramp Nordhaus (2007)
The Ramp • The climate-policy ramp (gradualist approach) • Based on output of “integrated assessment models” (IAM) • DICE: Dynamic Integrated Model of Climate and the Economy (Nordhaus and colleagues) • Mathematical model of economic growth accounting for the effects of global warming. • Dynamic economics: choices over consumption, working (labor), production, investment • Geophysical dynamics: emissionsgreenhouse gas stock climate change • Estimated reduction in gross world product: • 4.5o F 2%. -- 9.0o F 5% (Krugman, 2010)
Economic logic of the ramp • Given that “capital is productive and damages are far in the future … the highest-return investments today are primarily in tangible, technological, and human capital.” (Nordhaus, 2007) • Capital • Human capital: stock of skills and abilities of the labor force • Technological capital: the tangible means of production (machines, tools, facilities, equipment, infrastructure, etc) • Decision: • At each moment in time we can choose whether to “invest” any given dollar in • capital (human, technological, etc) or in • costly actions to reduce GHG emissions.
The Big Bang & the Stern Review (SR) • 2006: UK government releases a report: The Economics of Climate Change: The Stern Review, lead by Sir Nicholas Stern (Nobel Laureate) • SR estimates of costs of global warming are substantially higher than earlier estimates • Used similar data and methodology (IAM) • Review summary: • Unabated, climate change could result in an annual 5-20% decline in global output by 2100. • Comparison: US great depression – 1929-1930 real GDP fell by 9% • Costs to mitigate are around 1% of GDP • Policies for strong GHG reductions should be implemented immediately. • Why did the SR come to such a starkly different conclusion than the ramp? • Discounting (lower discount rate) • Damages (higher damages)
Discounting – Ramsey equation • Ramsey optimal growth model: • central framework for thinking about dynamic investment decisions • organizing principle for setting long-run discount rates • The Ramsey equation holds in the welfare optimum • r = ρ + ƞ *g Utility(c) low ƞ social rate of time preference/ utility discount rate real return on capital/ consumption disc. rate elasticity of marginal utility of consumption growth rate of consumption high ƞ ct ct+1 c: consumption growth, g • ƞ: specifies how quickly marginal utility falls as consumption rises.
Specifying a social discount rate for long-run climate policy analysis often employs the Ramsey framework Ramsey (1928) optimal growth model: Economy operates as if a “representative agent” selects consumption and savings to max PV of the stream of utility from consumption over time. One implication of the Ramsey model is the following equation: • r = ρ + ƞg • r: return to capital (real, long-run) • ρ: pure rate of time preference “time discount rate”, due to “impatience” • ƞ: elasticity of marginal utility w.r.t. consumption • g: average growth in consumption per capita
Two different perspectives on parameterizing the Ramsey discounting equation lead to very different results. ρ: pure rate of time preference; ƞ: elasticity of marginal utility w.r.t. consumption; g: average growth in consumption per capita • Descriptive approach/Nordhaus & the DICE model • Use economic data to estimate parameters: • Nordhaus (2008): • r = ρ + ƞg = 0.04 (average over the next century (Nordhaus, 2008, 10)) • 5.5% over first 50 years (61). • Economic growth and population growth will slow, rate will fall over time. • Prescriptive approach/Stern & the Stern Review (2006) • Argument: No ethical reason to discount future generations due to a pure rate of time preference except for the possibility that we might not be here at all (ρ reflects only ann. prob. of extinction). 1.3% growth assumed. • r = ρ + ƞg = 0.001 + 1*0.013 = 0.014
Nordhaus on Stern’s discounting approach Nordhaus (2008, p. 174)
Comparison of the discount rate Discount weight under various assumptions The level at any given time t represents the weight given to consumption arriving at year t. Discount weight
Damages SR used a level of GHG damage at the high end of the expected range. • The ratio of aggregate damages to the size of the economy ($D/$GDP) 100 years from now • commonly assumed: 1-4%. (Weitzman, 2007) • SR: >= 5% Nordhaus (2008, p. 51)
Some conclusions • Weitzman (2007): `On the political side … my most-charitable interpretation of (the Stern Review’s) urgent tone is that the report is … • an essay in persuasion… • that is more about gut instincts regarding the horrors of uncertain rare disasters whose probabilities we do not know… • than it is about (conventional) economic analysis. • SR might be right (“act now”) for the wrong reasons (due to bad model parameters instead of a careful analysis of uncertainty).’
The role of uncertainty in climate change policy—Weitzman (2009) • What happens to expected utility-based BCA for fat-tailed disasters? • Can “turn thin-tail-based climate-change policy on it’s head” (p. 2). • Concretely: a fat-tailed distribution over a climate sensitivity parameter (S) which maps CO2 changes into temperature changes. • Can drive applications of EU theory more than discounting (p. 5).
Economists often favor market-based instruments (MBI) • Advantages of MBI’s over C&C (Stavins, 1998): • Cost effectiveness (least cost) • Flexibility (within and between polluters) • Encourage behavior change through market signals rather than with explicit behavioral requirements. • Key attribute: MBI’s take advantage of private information that polluters have • RE: means and procedures they could use to reduce pollution • Stronger incentives for technological innovation
Cost effectiveness comparison over alternative instruments -- Clean Air Act
Carbon tax versus cap and trade: can accomplish essentially the same thing but with minor differences
Key design components for a cap and trade policy include:(1) cap, (2) scope, (3) allocation, (4) cost containment, & (5) offsets cap scope • [Newell, 2012]
Observed carbon prices over the last several years have been below $20/ton CO2 • [Newell, 2012]
Carbon offsets • Carbon offsets: a tradable credit for reducing carbon emissions by some amount (e.g. ton) generated outside a regulated system, recognized within a regulated system (e.g. a cap-and-trade regime) as a substitute for holding and using an emissions permit.
Attributes for carbon offset effectiveness Offset issues: is the offset… • Real: has the unit of emissions actually been avoided and not just claimed? • Additional: was the unit avoided due to the offset policy or would it have been avoided regardless of the offset mechanism? (Was this criteria satisfied in the “Cheat Neutral” ‘example’?) • Permanent: is the unit avoided permanently or only temporarily (e.g. will a planted tree just be burned in 10 years)? • Verifiable: can we ensure that each attribute above is actually attained so that stakeholders in the over-arching climate policy can ensure that the policy is not being undermined?
Offsets present substantial measurement challenges grey additional (action taken for payment) verifiable? permanent [Beede and Powers, 2013]
Problemswithadditionalityhavebeensubstantial. http://tocsin.ordecsys.com/ (2009) [Fig.: Newell et al. 2012; Data: Fenhann (2012)]
Measurement uncertainty doesn’t have to preclude mitigation projects f(y): probability density confidence yc: credited level y: true level of mitigation E(y): expected level confidence deduction • Verifiability of offsets: • Certainty? No. • Meeting or exceeding stated/credited levels with a specified level of confidence.
Managing carbon stocks as a global open access resource:game theory and the prospects for international cooperation
Mitigation goals will be difficult/impossible to achieve for rich countries acting alone [Nordhaus, 2010]
Game theory can provide traction on the “Tragedy” as a strategic action problem “Adam Smith was wrong.”
Game theory & international environmental agreements (IEAs) Game theory: the study of multi-agent decision problems where the payoffs to actions depend on the actions of others. A simplified story of the transboundary/international pollution problem: • Two countries, A & B, contribute to emissions of a transboundary pollutant. • Currently, neither A nor B is addressing the pollution issue but both are considering doing so • Discrete strategies: each country will choose either to contribute or shirk (not contribute) • Non-cooperative game theory: A & B will not negotiate but rather simply choose (irreversibly) a strategy. • Each behaves individually rationally • Information is complete: payoffs are fixed and common knowledge • Static, one-shot game: the actions of A & B are selected once, simultaneously, and are permanent. • Any “agreement” to take action must be self-enforcing—there is no higher authority to impose constraints. Finus, M. (2001)
The cost/benefit structure Assumptions: • Costs: • effective action: 4 total • If one country takes effective action (“contributes”) its costs are 4. • If both “contribute” then each faces a cost of 2. • no action: zero cost • Benefits • effective action: 3 each • Both countries receive benefits of 3 regardless of whether the effective action is due to the efforts of one or both countries • no effective action by either: 0 each **This example based on Keohane and Olmstead (2007, p. 79)
Assumptions: • Costs: • effective action: 4 total • If one country takes effective action (“contributes”) its costs are 4. • If both “contribute” then each faces a cost of 2. • no action: zero cost • Benefits • effective action: 3 each • Both countries receive benefits of 3 regardless of whether the effective action is due to the efforts of one or both countries • no effective action by either: 0 each The payoff matrix: for each possible outcome, the net benefits to each country are give by: (NBA, NBB) Country B Contribute Shirk Contr. Country A Shirk Note: payoffs to A depend on the choice of B and vice versa.