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New Climate-Economic Thinking

By Gernot Wagner and Martin L. Weitzman

Each ton of carbon dioxide emitted into the atmosphere today causes about $40 worth of damages. So at least says standard economic thinking.

A lot goes into calculating that number. You might call it the mother of all benefit-cost analyses. It's bean-counting on a global scale, extending out decades and centuries. And it's a process that requires assumptions every step along the way.

The resulting $40 figure should be taken for what it is: the central case presented by the U.S. Government Interagency Working Group on Social Cost of Carbon when using its preferred 3% discount rate for all future climate damages. But it is by no means the full story.

Choose a different discount rate, get a different number. Yale economist Bill Nordhaus uses a discount rate of slightly above 4%. His resulting price is closer to $20 per ton of carbon dioxide. The Stern Review on the Economics of Climate Change uses 1.4%. The resulting price per ton is over $80.

And the discount rate is not the only assumption that makes this kind of a difference. In Climate Shock, we present the latest thinking on why and how we should worry about the right price for each ton of carbon dioxide, and other greenhouse gases, emitted into the atmosphere. There are so many uncertainties at every step—from economic projections to emissions, from emissions to concentrations, from concentrations to temperatures, and back to economics in form of climate damages—that pointing to one single, final number is false precision, misleading, or worse.

Of course, that does not mean that we shouldn't attempt to make this calculation in the first place. The alternative to calculating the cost of carbon is to use a big fat zero in government benefit-cost calculations. That's clearly wrong.

Most everything we know about what goes into calculating the $40 figure leads us to believe that $40 is the lower bound for sensible policy action. Most everything we know that is left out would push the number higher still, perhaps much higher.

It's not over 'til the fat tail zings

As just one example, zero in on the link between carbon concentrations in the atmosphere and eventual temperature outcomes. We know that increasing concentrations will not decrease global temperatures. Thank you, high school chemistry and physics. The lower bound for the temperature impact when carbon concentrations in the atmosphere double can be cut off at zero.

In fact, we are pretty sure it can be cut off at 1°C or above. Global average temperatures have already warmed by over 0.8°C, and we haven't even doubled carbon concentrations from preindustrial levels. Moreover, the temperature increases in this calculation should happen 'eventually'—over decades and centuries. Not now.

What's even more worrying is the upper tail of that temperature distribution. There's no similarly definitive cut-off for the worst-case scenario. In fact, our own calculations (based on an International Energy Agency (IEA) scenario that greenhouse gas concentrations will end up around 700 parts per million) suggest a greater-than-10% chance of eventual global average warming of 6°C or above.

Focus on the bottom row in this table. If you do, you are already ahead of others, most of whom focus on averages, here depicted as "median Δ°C" (eventual changes in global average surface temperatures). The median is what we would expect to exceed half the time, given particular greenhouse gas concentrations in the atmosphere. And it's bad enough.

But what really puts the "shock" into Climate Shock is the rapid increase in probabilities of eventual temperatures exceeding 6°C, the bottom row. While average temperatures go up steadily with rising concentrations, the chance of true extremes rises rapidly:

Climate Shock Table 3.1

That 6°C is an Earth-as-we-know-it-altering temperature increase. Think of it as a planetary fever. Normal body temperatures hover around 37°C. Anything above 38°C and you have a fever. Anything above 40°C is life-threatening.

Global average warming of 3°C wouldn't be unprecedented for the planet as a whole, in all of it geological history. For human society, it would be. And that's where we are heading at the moment—on average, already assuming some 'new policies' to come into play that aren't currently on the books.

It's the high-probability averages rather than low-probability extremes that drive the original $40 figure. Our table links greenhouse gas concentrations to worryingly high probability estimates for temperatures eventually exceeding 6°C, an outcome that clearly would be catastrophic for human society as we know it.

Instead of focusing on averages then, climate ought to be seen as a risk management problem. Some greenhouse gas concentration thresholds should simply not be crossed. The risks are too high.

This kind of focus on temperature extremes is far from accepted wisdom. We argue it ought to be.

Gernot Wagner and Martin L. Weitzman are co-authors of Climate Shock (Princeton University Press, 2015). First published by The Institute for New Economic Thinking.

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Climate Shock in under 90 seconds

Think of the atmosphere as a giant bathtub. There’s a faucet—emissions from human activity—and a drain—the planet’s ability to absorb that pollution. For most of human civilization and hundreds of thousands of years before, the inflow and the outflow were in relative balance. Then humans started burning coal and turned on the faucet far beyond what the drain could handle. The levels of carbon in the atmosphere began to rise to levels last seen in the Pliocene, over three million years ago.

What to do? That’s the question John Sterman, an MIT professor, asked two hundred graduate students. More specifically, he asked what to do to stabilize concentrations of carbon dioxide in the atmosphere close to present levels. How far do we need to go in turning off the faucet in order to stabilize concentrations? Here’s what not to do: stabilizing the flow of carbon into the atmosphere today won’t stabilize the carbon already there at close to present levels. You’re still adding carbon. Just because the inflow remains steady year after year, doesn’t mean the amount already in the tub doesn’t go up. Inflow and outflow need to be in balance, and that won’t happen at current levels of carbon dioxide in the tub (currently at 400 ppm) unless the inflow goes down by a lot.

That seems like an obvious point. It also seems to get lost on the average MIT graduate student, and these students aren’t exactly 'average'. Still, over 80 percent of them in Sterman’s study seem to confuse the faucet with the tub. They confuse stabilizing the inflow with stabilizing the level.

Watch this video to avoid making the same mistake:

Excerpted from Climate Shock.

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What if bees had value?

Episode 5 of Paul G. Allen and Morgan Spurlock’s We The Economy explores the hidden value of natural capital:

A Bee's Invoice from We The Economy, starring Adrian Grenier, Gernot Wagner, Jodi Beggs, and Robert F. Kennedy Jr.

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World's Carbon Markets: EDF, IETA launch online resource on emissions trading programs

(This post first appeared on EDF Climate Talks.)

While Washington is stuck in gridlock, other jurisdictions around the world are moving forward on climate policy.

Market-based approaches to cutting carbon are in place in jurisdictions accounting for nearly 10% of the world’s population. Above: areas shaded blue have emissions trading programs that are already operating; areas in green have programs that are launching or being considered.

Market-based approaches to cutting carbon are already in place in jurisdictions accounting for nearly 10% of the world’s population and more than a third of its GDP. Many more jurisdictions are either moving ahead with market-based measures, or actively considering them.

As interest grows around the world, policymakers are increasingly seeking information about the range of existing and proposed initiatives.

In response, EDF has partnered with the International Emissions Trading Association (IETA), a trade association that represents businesses involved in carbon trading and climate finance, to launch The World's Carbon Markets: A case study guide to emissions trading.

The online resource provides detailed information about key design elements and unique features of 18 emissions trading programs that are operating or launching around the world.

EDF has also put together a quick reference chart that makes comparing the 18 programs even faster and easier.

Growing interest in emissions trading

Market-based policies are a proven way to limit carbon pollution and channel capital and innovation into clean energy, helping to avert the catastrophic consequences of climate change.

While emissions trading programs around the world, like the ones we have looked at in detail, vary in their features, they all share the key insight that well-designed markets can be a powerful tool in achieving environmental and economic progress.

The countries, states, provinces and cities highlighted in this report, which are moving ahead with strong action on climate change, constitute a vital and dynamic world of “bottom-up” actions that complement multilateral efforts such as the ongoing United Nations climate negotiations.  Jurisdictions considering market-based approaches can use this new resource to learn from their growing number of peers already headed in that direction.

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Single-action bias

We all want to do something, anything. We don't just want to sit idle and watch events unfold around us. Call it "action bias."

Then there's "single-action bias."

We all want to do something, anything, but once we've done that one thing, we move on. For something as intractable and complex as global warming, that's a real problem.

Yes, replace your inefficient incandescent light bulb with more efficient compact fluorescent ones, but don't believe for a second that single action solved the problem.

Recycle. Just don’t think it’ll stop global warming. Make the planet notice.

For daily musings like these, take a look at EDF economist Gernot Wagner's personal blog.

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Jobs, jobs, jobs

Co-authored with Nat Keohane.

Marc Gunther lists ten reasons why "Cancun can’t." We won't go into his other nine points here, but number three on the list hit home:

Environmentalists have been disingenuous about the climate issue. They’ve argued that regulation of carbon dioxide will create green jobs and grow the economy. Typical is this graphic from Environmental Defense. (“Get a step-by-step picture of how a carbon cap will spark new jobs, lift the economy and clean the air.”) Uh, no. Most economists agree that dealing with global warming will entail short term costs. (See Eric Pooley’s excellent analysis at Slate.)

Talking about jobs is one of the most difficult things to do well in the arena of climate policy. The jobs issue is highly politically charged—and for good reason, given the state of the economy. But it struck us as unfair for Marc to use EDF as his bête noire.

To begin with, the graphic that Marc links to doesn’t make the claim he ascribes to it. We weren’t saying that climate policy was a free lunch. What we were pointing out was that doing something about climate can also create good jobs in some unexpected places. More on that in a minute.

We have bent over backwards to be as balanced and rigorous as possible in our assessment of the economics of climate change.

This turns out to be perfectly illustrated by Eric Pooley’s analysis—the same one Marc links to.

Eric's indeed excellent analysis makes two points:

First, there is a broad consensus that the cost of climate inaction would greatly exceed the cost of climate action.

That's the main, often-forgotten point because it seems so obvious: "it's cheaper to act than not to act."

We should really stop here and reflect on that for a second. Many—if not most—economists do, in fact, agree on that statement and have for a while.

But that's not our point here, either. Read More »

Also posted in Cap and Trade, International, Politics| 1 Response
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