Thursday, March 18, 2010

Richard Tol: The feasibility of two degrees

Guest comment by Richard Tol

In 1995, the Scientific Council of the German Federal Government for Global Environmental Changes (WBGU) recommended that it would be appropriate to keep the global mean surface air temperature below a two degrees Celsius warming relative to the start of the industrial revolution. The “two degrees target” was adopted by the German government and the European Union; and has been endorsed by the G8 and noted by the United Nations.

Two degrees is a vague target. With or without natural variability? Can we exceed the target in the interim or not? For sure or with a 50% probability? Let us assume that the target is without natural variability, in the long run, and with something like a 50% chance. (Note that this makes the target softer.) This means that anthropogenic radiative forcing should not exceed some 2.5Wm-2.

The forcing from long-lived greenhouse gases is already at 2.6 Wm-2. Total anthropogenic forcing is 1.6 Wm-2 – but we want to get rid of aerosols because of concerns about health and environment. Therefore, the two degrees target is very tough.

The Energy Modeling Forum (EMF), hosted at Stanford University, organises model comparisons for climate economists. The latest exercise, EMF22, was about stringent climate targets. Fourteen models from around the rich parts of the world participated. The results are published here (open source). More accessible material is here.

The following results emerged on the two degrees target. Six out of fourteen models simply could not meet the target whatever was tried. The other eight impose the following conditions on meeting the target:
1. All countries will have to start reducing emissions by 2020;
2. The price of carbon in 2020 in all countries for all emissions should be at least $15/tCO2 (roughly what it is today in the regulated half of Europe), but may need to be as high as $263/tCO2;
3. Emissions from rich countries will have to be around 20% of their 2000 levels by 2050 and emissions from poor countries will have to be round 50% of their 2000 levels by 2050;
4. There are no constraints on the expansion of carbon-neutral energy, such as wind or nuclear power.
If any of these conditions are violated, then carbon-negative energy is needed. Carbon dioxide emissions in 2000 were some 25 GtCO2. In 2100, this would need to be -15 GtCO2 – that is a reduction of 160%. This would require providing a large share of the world’s energy needs by biomass (without affecting world food supply) and carbon capture and storage at a massive scale. This places a lot of faith in technologies that have yet to be demonstrated.

I would be surprised if any of these conditions are met, let alone all. I therefore think that the two degrees target is infeasible.


_Flin_ said...

It seems to me that some links went missing in these sentences: "The results are published here (open source). More accessible material is here."

richardtol said...


Werner Krauss said...

Puuh, that looks bad, indeed. However, what is the use of calculations that are based on so many hypothetical assumptions? The 2 degree goal is not 'infeasible'; instead, it is nonsense. Right?

richardtol said...

Many analysts used to ignore the two degrees target as just another wild plan by the EU.

But then it got political legs, and the IPCC same along:

Now we make our models commit unnatural acts.

Werner Krauss said...

Would you agree: The imperfections of the peer review process in the IPCC report are a minor problem compared to the implausibility of the political targets such as the 2 degree goal.
What I want to say: as the science concerning the basic understanding of anthropogenic climate change is mostly settled (Hans von Storch), the political targets / goals / conclusions are what is really at stake. Of course, the political dimension in turn influences the quality of science. The 2 degree goal almost naturally invites catastrophic scenarios; a diversified political strategy (punctual adaptation strategies; focus on production of carbon free energy; higher investment in R&D etc) would invite more 'realistic' and less catastrophic scenarios.

By the way: models always commit unnatural acts; to pretend that they don't leads consequently to climate determinisms such as '2 degree limit or apocalypse!'

Anonymous said...

Yes, If we accept the IPCC central estimate of 3 C for climate sensitivity, then the 2 C target is almost impossible to meet.

But there's some good news. As Lucia Liljegren at the Blackboard is showing in various ways, the IPCC number is almost certainly an overestimate.

And small adjustments to the climate sensitivity downwards will have a much more powerful effect than any co2 reductions conceivable. At least within the next 40 years.

A real world sensitivity of 2 C or lower will automatically transform the risk of catastrophy into a benign warming.

This is why the estimate of climate sensitivity is so important and so forcefully contested. The 3 C must not be questioned.

Jonas B1

richardtol said...

Yes and no. If the IPCC had been a proper advisor, it would have highlighted that the political goals are implausible. Instead, the IPCC choose to reinforce the notions (1) that there are monsters beyond two degrees and (2) that emission reduction is easy and cheap.

Sure. If the climate sensitivity is lower (higher), two degrees is more (less) feasible.

_Flin_ said...

What do you all see as the exact problem?

Point 1 can happen. It depends on the USA, China and India. The EU already reduces CO2 emissions, according to the EEA report 9/2009.

Is there any problem with point 2? Isn't it a question of policy to set a price on carbon?

Concerning 3: Europe is already reducing. If the USA takes emission reduction serious, they have a lot more potential than other countries, if only for their high per capita use of CO2. So why shouldn't 20% be feasible until 2050? (I wondered about the 50% for poor countries, though. Isn't it easier to reduce emissions where there are many? Or is this due to the marginal costs being the control knob?)

So the decisive point is 4. What are the constraints in your opinion? Are we already using the technologies available to us or have we just started? When I look around my street, everyone uses gas for heating, some use oil. 1 heat pump exists. In my county, the third geothermal plant just got online, although only one of them has hot enough water for electricity, the rest are for district heat. But this can be improved by using existing technology like Organic Rankine Cycles. Or take LED Lamps. Lighting controlled with measuring current brightness. Servers that shut down or slow down when not used. Cars that drive farther with the same amount of gas.
The efficiency potential is immense. And we have just started to use it.

Doesnt it comes down to policy in the end? Set the price for CO2 high enough and it is not a question of possibility but of profit.

mheimann said...

"The EU already reduces CO2 emissions,...", yes, but as I mentioned already in a previous thread, only because we outsource the emissions to China. Where are your Nike shoes and your t-shirt coming from? Check this out:
Davis and Caldeira, PNAS (doi:10.1073/pnas.0906974107)

richardtol said...

2. So you think there is non-zero probability that China in 2020 will have a carbon tax that is, say, ten times the current price of CO2 in Europe?

3. In order to get to 80% emission reduction, we'd need to go 100% in power generation as that's where abatement is cheapest and easiest. Power plants have a life-time of 40 years or more. At the moment, Europe is still building new gas-fired power plants. These will still be there in 2050, so electricity will not be carbon-neutral.

4. You may want to have a look at German objections to nuclear or English objections to wind.

Anonymous said...

How many degrees are the "temperature preindustrial level"?
How was it established?
Two degrees above how many degrees?

Marco said...

@Jonas B1:
I'm looking forward to Lucia's rebuttal in the literature of the large range of papers that get to the 3 degrees climate sensitivity.

Put I'm not holding my breath she will even try and publish it...

@ReinerGrundmann said...

"Set the price for CO2 high enough and it is not a question of possibility but of profit."

The problem with the current structure of the economy is that profits are linked to jobs, which are linked to economic growth, which is linked to carbon prices ...
If you want to reduce carbon by reducing profits you price whole segments of the population out of their jobs and other parts of the world out of access to electricity. Politicians know this. For this reason you cannot rely on them setting the price high enough if this means they will lose the vote.

This is where I have a question for
How convincing are scenarios for "green growth"?

richardtol said...

Is the question "How likely is it that massive government intervention in and substantial subsidies to the energy sector will accelerate economic growth?" or "How likely is it that certain companies will reap large rents from such policies?" or "How likely is it that future energy supply will be less carbon-intensive than today's?"

Close to 0, close to 1, and 90%, respectively.

Marco said...

The German coal industry currently receives 70,000 euros of subsidy *per employee* (2.5 billion a year, 34000 employees). It's actually cheaper for the government to have these people on social security!

There are quite a few other countries where fossil fuel industries get amazing amounts of subsidies, including the US.

Sadly, when renewable energy is discussed, everyone points to the subsidies, but the subsidies to nonrenewables is forgotten.

@ReinerGrundmann said...

my question had employment levels in mind, which are based on less carbon intensive industries. Can you point to studies that have been done?

@ReinerGrundmann said...

this may be true but does not invalidate my argument.

richardtol said...

See (now conditionally accepted)

In short, job creation in green energy would be offset but job destruction in brown energy. Dearer energy means slower job creation in the rest of the economy. The latter effect dominates.

Rob Maris said...

@ Reiner/13:
"... whole segments of the population out of their jobs and other parts of the world out of access to electricity. Politicians know this. For this reason you cannot rely on them setting the price high enough if this means they will lose the vote".

This shows a weak point of democracy. But we won't give up this system (most of us, I guess), so it heavily depends on the courage of politicians together with ngo's and media to tell an unconvenient truth, as to cite Gore.

It is true that profit is linked to jobs, but currently jobs are also killed due to automation etc. When you see that politicians ignore even this fact - still believing in full occupation - I have not much confidence regarding our future.

One can also tell unconvenient truths as having positive side-effects, as practized recently by worldwatch. Look as this (german) site about this:

This worldwatch issue completely coincides with ideas of Prof. Egbert Tellegen / Utrecht(NL): "We are living in an age where consumers cannot keep track of production volumes, instead of the reverse way. We MUST consume, not because we need the products, but because otherwise stock values fall and the employees will lose their jobs."
"total taboo-issue: income. A high income is very bad for the environment." - he points out that a narrow correlation between environment impact and income exists (note: shorted translation by me).

Conclusion: when politicians won't act regarding economic restructuring due to a couple of other causes, we'll get in severe trouble, even before climatic changes will infer our way of life.

_Flin_ said...

@Reiner Grundmann: "If you want to reduce carbon by reducing profits you price whole segments of the population out of their jobs and other parts of the world out of access to electricity."

I do not intend to reduce profits. I intend to reduce profits that are made by damaging public goods. Right now we all (= the world) have to pay for the damages that are caused by emission of CO2. The profits go to the shareholders and employees of the companies emitting CO2.

The damages exist and will increase. They are very hard to allocate. How big are the damages to the north german tourism industry because warm sea water leads to a belt of jellyfish around the islands? How big are the damages to coffee exporters because of changing climate? Are they balanced by the higher profits for... let's say... canadian farmers?

Are jobs for Appalachian coal miners and Kuwaitian construction workers in any way better than those for Kansas wind turbine technicians and Columbian coffee farmers? Probably depends on whether you ask the Senator from Kansas or from West Virginia.

So the profit statement I made was more about ways of producing clean energy, transporting goods efficiently or saving energy becoming profitable enough to invest in and thus creating new jobs. And not so much about reducing profit for anyone.

@Richard Tol:
Concerning 2: no. That is zero probability.

Concerning 3: I think I misread your statement. I mixed up "20% of year 2000" with "20% lower than 2000" and was thinking: What is the problem with that. 20% of 2000 is... well... impossible. Looks like we are in quite some trouble. So the communication towards policy should probably be more like: "You've made your bed, now you must lie in it" instead of "Everything will be ok if we act now".

Concerning 4: Yes, the german Green parties nuclear <-> climate policy remains a mystery to me, too.

Hans von Storch said...

_Flin_ - what is this "damages to the north german tourism industry because warm sea water leads to a belt of jellyfish around the islands"? Where do you have that from? This would mean that we would have now more jellyfish than in my childhood. Do we? What about other drivers, such as eutrophication? -- Hans

isaacschumann said...

A related article in the Guardian today from the U.N. ambassador of Bolivia:

He states:

"the commission confirmed that the pledges by developed countries are equal to between 13.2% and 17.8% in emissions reductions by 2020 – far below the required 40%-plus reductions needed to keep global temperature rise to less than 2C degrees."

This is supposedly a "dargerous approach" that will "condemn millions."

To me, these calculations; what level of CO2 will produce what amount of warming, what real world effects this warming will have, are too arbitrary to be as central to the debate as they are. Its not that I think we should not consider these questions, just that they are treated with far more certainty than I believe exists at the moment.

And to Richard, what is your opinion of the feasibility and costs of a 40% or even 20% reduction from 1990's levels by 2020? Thank you. To me, there seems a disconnect here.

isaacschumann said...


Apologies, your post makes clear your opinion on the feasibility of these targets.

But what would the real world implementation of these targets look like? What level of carbon price/regulation etc. would be needed to meet these levels? I would imagine them to be quite severe. It seems a political pipe dream that an elected government could impose these conditions.

richardtol said...

Follow the first link in the original post.

_Flin_ said...

@Hans von Storch: The last time I was there, which was in 2002, there was a belt of small jellyfish around every island I went (Sylt, Amrum, Hooge, Föhr). About 2m wide and 1m deep.

While there are of course other causes for that as well (less fish and natural enemies, too much fertilization), rising temperature and longer reproduction cycles is one of them.

The example was just for something rather far fetched where damages might exist because of AGW, but if there are, it's hard to allocate and quantify. Probably would've made more sense if the example had been the burning of Greece in 2007.

isaacschumann said...


Thanks, the carbon tax rates explored in krey and riahi do indeed look prohibitively high for more aggressive scenerios.

I take from your piece that it is better for all countries to begin mitigation now as this is more effective since radiative forcing from ghg's will increase faster because of reduced participation making future abatement more expensive? very interesting, please correct me if I am incorrect in this assessment.

P Gosselin said...

eduardo said...


Dear Marco,

correct me if I am wrong, but the reason why the coal industry in Western Europe receives public subsidy is to protect it from foreign competition due to cheaper foreign coal and lower foreign labour costs, not because the production costs of coal-based electricity are higher than from renewable sources. The latest figures I read for production costs were something like 5 cents Kwh for coal, wind about 10 cents, and thermal solar about 50 cents per Kwh.

You are right that those subsidies do not seem to make economic sense and aim at conserving an energy source for political/strategic/electoral reasons. This highlights how difficult an energy transformation really is: we have on the one side the German Chancellor boasting her Green credentials and on the other side the German government subsidizing German coal

Marco said...

I can't think of any country that does *not* subsidies its coal industry.

What I wanted to indicate is that you have the paradox of providing enormous subsidies so a national production can be competitive on the world market (I don't think you get even close to 5 cents/Kwh for German coal when taking the subsidies into account), while at the same time also introducing national taxes to get the product out of the national market. You could also provide the subsidies to the national renewable energy sources, thus making it competitive versus coal. But I know that economists will have all kinds of objections to that.

Regarding the subsidies: Merkel at least took the discussion to phase out the coal subsidies.

Jonas Bhend said...


According to, Germany produces some 600TWh per year. Thus the subsidies of 2.5 billion Euro per year affect the price by only fractions of a cent.

Marco said...

Hmmm, apparently I've made a factor 100 error somewhere. Thanks. Shouldn't do any calculations before 8 am, I guess!

(but do note that the 600 TWh is for the total energy production, not for coal alone).

_Flin_ said...

NZZ said in 2007 that the price to produce a ton of Steinkohle is 160 Euros. With 8141 kWh per ton and an average German degree of efficiency of 38% for coal plants thats 5,17 €-cent/kWh without accounting for the plant. So actually producing the power is probably more in the range of 7,50 €C/kWh. Without external costs for CO2.

So German coal is more expensive than wind (which is actually a funny statement to make, when I think about it).