## New IPCC Report (Part 6)

guest post by Steve Easterbrook

(6) We have to choose which future we want very soon.

In the previous IPCC reports, projections of future climate change were based on a set of scenarios that mapped out different ways in which human society might develop over the rest of this century, taking account of likely changes in population, economic development and technological innovation. However, none of the old scenarios took into account the impact of strong global efforts at climate mitigation. In other words, they all represented futures in which we don’t take serious action on climate change. For this report, the new ‘RCPs’ have been chosen to allow us to explore the choice we face.

This chart sums it up nicely. If we do nothing about climate change, we’re choosing a path that will look most like RCP8.5. Recall that this is the one where emissions keep rising just as they have done throughout the 20th century. On the other hand, if we get serious about curbing emissions, we’ll end up in a future that’s probably somewhere between RCP2.6 and RCP4.5 (the two blue lines). All of these futures give us a much warmer planet. All of these futures will involve many challenges as we adapt to life on a warmer planet. But by curbing emissions soon, we can minimize this future warming.

(Fig 12.5) Time series of global annual mean surface air temperature anomalies (relative to 1986–2005) from CMIP5 concentration-driven experiments. Projections are shown for each RCP for the multi model mean (solid lines) and the 5–95% range (±1.64 standard deviation) across the distribution of individual models (shading). Discontinuities at 2100 are due to different numbers of models performing the extension runs beyond the 21st century and have no physical meaning. Only one ensemble member is used from each model and numbers in the figure indicate the number of different models contributing to the different time periods. No ranges are given for the RCP6.0 projections beyond 2100 as only two models are available.

Note also that the uncertainty range (the shaded region) is much bigger for RCP8.5 than it is for the other scenarios. The more the climate changes beyond what we’ve experienced in the recent past, the harder it is to predict what will happen. We tend to use the difference across different models as an indication of uncertainty (the coloured numbers shows how many different models participated in each experiment). But there’s also the possibility of ‘unknown unknowns’—surprises that aren’t in the models, so the uncertainty range is likely to be even bigger than this graph shows.

You can download all of Climate Change 2013: The Physical Science Basis here. Click below to read any part of this series:

Climate Change 2013: The Physical Science Basis is also available chapter by chapter here:

### 42 Responses to New IPCC Report (Part 6)

1. L Hedding says:

Hard Facts on China
China has 19% of the world’s population, but consumes…..
53% of the world’s cement
48% of the world’s iron ore
47% of the world’s coal
…. and the majority of just about every other major commodity.
By 2010, China produced 11 times more steel than the United States.
New World Record: China made and sold 18 million vehicles in 2010.
There are more pigs in China than in the next 43 pork producing nations combined.
China currently has the world’s fastest train and the world’s largest high-speed rail network.
China is currently the number one producer in the world of wind and solar power, but don’t use it themselves. While they manufacture 80% of the world’s solar panels, they install less than 5% and build a new coal fired power station every week. In one year they turn on more new coal powered electricity than Australia’s total output.
China currently controls more than 90% of the total global supply of rare earth elements.
In the past 15 years, China has moved from 14th place to 2nd place in the world in published scientific research articles.
China now possesses the fastest supercomputer on the entire globe.
At the end of March 2013, China accumulated US\$4.04 trillion in foreign currency reserves
–the largest stockpile on the entire globe.
Chinese people consume 50,000 cigarettes every second …
They are already the largest carbon dioxide emitter and their output will rise 70% by 2020.

• John Baez says:

The facts about China are interesting, and clearly China and India are crucial in the fight against global warming… but it is not true that it “will not make one iota of difference” what anyone does in the United States. Even if only the US were emitting CO2, we would have a significant problem. Canada and Australia are minor by comparison:

(Click for details.)

You may not know that discussion of partisan politics is forbidden on this blog. For this reason, I’ve deleted the paragraph containing your claims that “the Left believes the planet can be ‘saved’ by destroying America and the West”, and that “internal enemies have sworn to destroy every vestige of freedom and happiness”. I didn’t do this because I believe these claims are false, just because they’re not on topic for this blog. There are many other blogs for discussing politics.

The World Resource Institute (which is amongst others funded by a not negligible quantity by Shell Foundation) has a chart with more countries. In this chart the TCO2e per capita is listed and if I looked correctly the winner is:

Kuwait 65.68

followed by

Brunei 53.30
Singapore 46.17
Qatar 42.69

• John Baez says:

I think these high figures come from oil refining, somehow. I don’t think people in Singapore use much more energy per capita than people in the US (more air conditioning, less driving), but it’s a small country with a lot of oil refineries. You can see flares of burning ‘waste’ petroleum products at night!

I think these high figures come from oil refining, somehow. I don’t think people in Singapore use much more energy per capita than people in the US (more air conditioning, less driving), but it’s a small country with a lot of oil refineries. You can see flares of burning ‘waste’ petroleum products at night!

This seems to be at least partially also to be the case for the other countries in my above list of most CO2 producing countries, if you include gas. Like Trinidad and Tobago seems to be mostly a gas than oil producer(?) and so I assume that they refine on the spot. Singapore seems however to import oil and gas (?). Where from? From Brunei?

Would be interesting to know in how far the import/export balance and the kind of “produced” or “refined” goods is taken into account in the CO2 negotiations. A country which doesn’t have enough land to feed its inhabitants has to refine and export. I guess this is the case for Singapore and by the way also for Germany. That is according to e.g. this newspaper the land needed for feeding a German with vegetarian food (!) is 2500 square meters (sorry couldn’t find the official source). That is for roughly 8 × 107 inhabitants one would need 2 × 1011 m2, but there are altogether just about 3.5 × 1011 m2 land alltogether in Germany. And even if you leave industrial areas away, that is even if one would return to a preindustrial economy, you need places for housing and roads (last but not least also for European through traffic) and for some wildlife habitats in order to keep at least some animal species alive. (I missed that aspect somewhat in the criticism about Germany’s exports.) Would be interesting to know whether this problem is also related to the purchase of farm land in foreign countires like in Africa or the Ukraine (by the way in east or west Ukraine?).

I tried more to get reliable information on the nutritional land need per person, however with no real success so far.

I found though a list of global arable land per person at world bank, which confirmed the information given at the blog “2000m2” that there is globally $2000 m^2$ of arable land per person available. This is somewhat in “dissonance” with the above need of $2500 m^2$ for an average veggie german.

• Graham Jones says:

Some figures for the UK. Total area 24Mha, population 63M. 11.5Mha is grass for livestock, 2.5Mha is food for livestock, 2.5Mha is food for people. That makes 16.5Mha/63M = 2600m2 each. The UK is 60% self-sufficient in food. ZCB says we could halve the area devoted to food production if we went mostly veggie.

Sources:

• Graham Jones says:

I meant to say: ZCB says we could halve the area devoted to food production and become 83% self-sufficient if we went mostly veggie.

Thanks Graham,

I found some of the assertions in the proposal of ZCB regarding food not fully comprehensible (like fish is recommended, where there is already a problem with overfishing) and the proposal was not very clear in how exactly the substitution of animal proteins should work (which crops, how much land use do these need etc. – like I could see problems in winter at least here in Brandenburg) but finally it is good to think about this in general.

I wrote:

That is according to e.g. this newspaper the land needed for feeding a German with vegetarian food (!) is 2500 square meters (sorry couldn’t find the official source).

I cited wrongly that is the newspaper wrote “mostly vegetarian” and actually it turned out this is a false information.
The article doesn’t say how big the need would be with purely vegetarian food.
That is the Landesanstalt in Baden now friendly sent me a link to the original article by Atsuko Wakamiya in the magazine Oekologie &Landbau Nr. 159, Ausgabe 3/2011.

According to this article the 2500 m2 are referring to the current consumption patterns of an average german, which means for a lot of germans: too much meat. With a recommended meat consumption the need would be around 1081 m2 according to the article:

Beispielsweise empfiehlt die Deutsche Gesellschaft für Ernährung (DGE) 300 bis 600 Gramm Fleisch pro Woche (DGE, 2010) zu essen. Daraus ergibt sich eine jährliche Obergrenze von etwa 31 Kilogramm.

and

Wie würde der Flächenbedarf aussehen, wenn nur so viel tierische Lebensmittel wie empfohlen gegessen würden? Basierend auf den von Woitowitz (2007) berechneten verringerten Verzehrmengen ermittelt die Studie einen halbierten Flächenbedarf für die Produktion tierischer Produkte; er re- duziert sich von 2.143 auf 1.081 Quadratmeter (Tab. 2).

The newspaper eventually erred because the above statistics was made for organic food.

Die analysierten Daten zur Produktionsweise beziehen sich auf die ökologische Landwirtschaft.

and a lot of people set organic equal to vegetarian.

Organic farming has a lower yield (which might at least partially be due to the fact that often organic farmers are at not so good locations) and is more labour intense, but according to a recent EU study(via 2000m2 ) that doesn’t necessarily mean less profits:

Organic farming practices are more extensive, except when it comes to labour input, so yields are lower, but the higher prices make up for this.

In sum, there is no clear pattern in performance: each country and sector has different rates of income per annual work unit
.

• Graham Jones says:

I’m glad the German figures are now more consistent with UK figures. On the forum, I just posted something about agriculture and diet.

Would be interesting to know in how far the import/export balance and the kind of “produced” or “refined” goods is taken into account in the CO2 negotiations. A country which doesn’t have enough land to feed its inhabitants has to refine and export.

One should also note at this place that “meat production” (this is also meant as a reference to a comment I made later) should probably account for as a kind of “refinement” in this context. In particular a new study in which

Researchers calculate ‘hidden’ emissions in traded meat it is found that:

“Our analysis of livestock emissions embodied in the international trade of meat highlights the regional variation in emissions intensities and quantifies a significant barrier to effective regional and national policies regulating livestock emissions.

“A developing country, for example, may lack specific infrastructure and therefore emit large amounts of GHGs when producing meat from livestock. These emissions can be increased when demand from more developed countries is placed on this country to produce more meat.

(side remark: Germany seems to be exporting meat to Italy:

In Europe, meat exported from France to Italy and Greece embodied 1.4 Mt and 1.2 Mt of CO2-eq emissions respectively, and Italian imports of meat from Poland, Germany and Netherlands embodied 0.7, 0.6, and 0.7 Mt of CO2-eq emissions, respectively.

)

Unfortunately with the fall of customs and not much other mechanisms in sight to easily track down the origins and pathways of products it will be hard to invigorate better investigations of the involved costs and balances let alone invigorate political measures, which reflect the involved balances accordingly. That’s amongst others also why I critized the CETA trade negotiations here on this german blog (and signed a protest against it).

The seclusion of the origin and pathways of a product may have -especially with respect to food production- of course eventually even worse unpleasant consequences.

• John Baez says:

Singapore seems however to import oil and gas (?). Where from? From Brunei?

They probably import it from many places. Let’s see… Wikipedia says:

Singapore was the top 10th country in oil imports in 2008: 50 megatonnes. For comparison, oil imports in Spain were 77 megatonnes (the top 8th country, with a population of 45.59 million) and in Italy they were 73 megatonnes (the top 9th country, with 59.89 million persons).

But where does it come from? The Singapore government will tell me the amount of exports by country and the amount of non-oil exports by country, so I could subtract those to find the amount of oil exports, but I want oil imports.

And I’m not even sure that oil refining is responsible for Singapore’s big carbon footprint.

• Robert Smart says:

This fails to mention that China is putting serious effort into advanced nuclear power, which is our best (perhaps only) chance to make fossil fuels unnecessary.

2. arch1 says:

Does anyone have good pointers to something like a global warming Beaufort scale? E.g. more than just predicted sea level rise.

It would be especially interesting to see such a scale ranging into negative deltas (not just positive ones), both for context and because this would force contact w/ historical reality.

3. Martin Lewitt says:

Once again, that is not an uncertainty range in the chart, it is just a range of model results. No attempt has been made to account for the uncertainty introduced by the known knowns, much less the unknown unknowns. There is a wealth of diagnostic literature documenting known issues with the models. I realize you are just presenting what the IPCC claims errors and all and not vouchsafing its correctness but did the IPCC actually try to claim that was an uncertainty range, or is that your addition?

• John Baez says:

Martin Lewitt wrote:

Once again, that is not an uncertainty range in the chart, it is just a range of model results.

[…] did the IPCC actually try to claim that was an uncertainty range, or is that your addition?

Steve said what the error bars mean in the graph here. In the caption he wrote:

Projections are shown for each RCP for the multi model mean (solid lines) and the 5–95% range (±1.64 standard deviation) across the distribution of individual models (shading).

In simpler English: the solid line is the average of the temperatures all the models predict. The shaded region includes what 90% of the models predict… leaving out only the hottest 5% and the coldest 5%.

(Fig 12.5) Time series of global annual mean surface air temperature anomalies (relative to 1986–2005) from CMIP5 concentration-driven experiments. Projections are shown for each RCP for the multi model mean (solid lines) and the 5–95% range (±1.64 standard deviation) across the distribution of individual models (shading). Discontinuities at 2100 are due to different numbers of models performing the extension runs beyond the 21st century and have no physical meaning. Only one ensemble member is used from each model and numbers in the figure indicate the number of different models contributing to the different time periods. No ranges are given for the RCP6.0 projections beyond 2100 as only two models are available.

4. David Lyon says:

What does this study showing that the United States is an oligarchy, not a democracy mean for choosing our future? If political power comes from money, and many of the most profitable companies globally are oil companies, can they be meaningfully opposed? If anything, oil will become more profitable as demand increases while supply decreases over the next 20 years.

• John Baez says:

The Carbon Tracker Initiative argues that there’s a ‘carbon bubble’: a lot of fossil fuel assets that are overvalued because there’s a limit to how much carbon we can burn without pushing temperatures 2 °C above their pre-industrial level.

John Fullerton summarizes the idea thus:

• The Potsdam Institute calculates that in order to reduce the risk of exceeding 2 degrees Celsius warming to a 20 percent chance (not all that comforting), the global carbon budget for 2000 – 2050 cannot exceed 886 GtC02. Minus emissions in the first decade of the century, this leaves a budget of 565 GtC02 over the next 40 years.

• Total “proved” fossil fuel reserves listed on public company balance sheets and State reported reserves is estimated at 2795 GtC02, nearly 5 times the remaining budget, implying 80 percent of these reserves should be left in the ground.

• Seventy four percent of these reserves are State owned (Russia, China, Saudi, Venezuela, Iran, Iraq, etc.) or owned by private companies, 26 percent are owned by the 200 largest public energy companies.

According to James Leaton at Carbon Tracker, the market value of the top 100 public oil and gas companies and the top 100 public coal companies listed in the report exceeds \$7 trillion, approximately 12% of the global public equity market. Making a simple assumption that State-owned companies and reserves have an equivalent market value per unit of carbon would suggest the global market value of proved fossil fuel reserves equals \$27 trillion.

A real cap on carbon emissions designed to limit warming to two degrees implies sovereign states and public corporations will need to strand 80 percent of their \$27 trillion of proved reserves. Rounding down, this implies a potential \$20 trillion write off.

Carbon Tracker calls these \$20 trillion of carbon ‘unburnable’. However, this is optimistic. We can also imagine this carbon as \$20 trillion worth of arguments that we should keep burning fossil fuels.

This is why some of us should prepare for the consequences of a very dangerous ‘business as usual’ scenario.

• Bruce Smith says:

Isn’t this argument ignoring the possibility of more expensive ways of burning the oil which don’t emit CO2 into the atmosphere? As long as some process like that is feasible as an energy source, it only makes the oil have less value, not no value. And with energy prices presumably going higher (since at present prices demand would outstrip supply, under these assumptions), profits of the resource owners would not necessarily be lower at all.

To me, the main argument for such a bubble would instead be that the current valuation assumes oil is the main practical future energy source. That same \$20 trillion could buy a lot of R & D and investment in alternatives.

BTW I agree with your fear that protecting \$20 trillion of hoped-for value can justify paying for a lot of lobbying (etc).

• John Baez says:

Bruce wrote:

Isn’t this argument ignoring the possibility of more expensive ways of burning the oil which don’t emit CO2 into the atmosphere?

Yes, I guess so. The Carbon Tracker website says:

Climate scientists (Meinhausen et al 2009) have calculated that if 886 Gt CO2 is released globally during the period 2000 – 2050, there is a 20% chance global warming will exceed 2°C. In 2011, we have already burnt over one third of this 886 Gt CO2 budget, and the known fossil fuel reserves easily exceed the remaining allowance. The reserves beyond this limit are what we refer to as unburnable carbon.

This neglects developments such as carbon capture and storage for coal-fired power plants, which we’ve been writing about on the Azimuth Wiki.

For example, according to Nature, in 2009, the government-owned Huaneng Group opened a carbon capture facility at an existing power station:

The system scrubs roughly 120,000 tonnes of CO2 a year from 3% of the facility’s flue gases, but what has caught everybody’s eye is the cost that Huaneng quotes: a mere US\$30–35 per tonne of CO2, including the further expense of purifying the captured gas for use in the food and beverage industry.

That is far below the \$100 or more typically estimated for first-generation projects to retrofit existing power plants for carbon capture and storage (CCS) in the United States and Europe, and it is within the range of past carbon prices in the European Union emissions trading system.

This press release announced a plant to determine the potential feasibility of applying Huaneng Group’s low-cost carbon capture process at unit 3 of Duke Energy’s Gibson Station in Indiana:

• Duke Energy, Duke Energy and China Huaneng Group expand cooperation to develop carbon capture and sequestration technologies, 13 February 2012.

• There is an interesting exchange of posts on the fact that cost of climate mitigation is supposedly very low (0.06% of GDP).

While I agree with the fact that more growth doesn’t necessarily mean “more stuff”, I find hard to reconcile this finding with the “common sense” notion that reaching an 80% target for energy (electrical only, i guess, but not sure) coming from low carbon supplies by 2050 (in just 35 years) must be a near-monumental achievement.

I also tend to disagree with Krugman’s statement that

In fact, it’s possible that solar will displace coal even without special incentives.

The cost of solar panel module is only a fraction of the total cost needed to install solar power, other costs like installation, maintenance, replacement after 20 years or so, and the opportunity cost of not being able to use the land in any other way must also be considered. And, above all, currently to keep the grid stable more than half of electrical energy supply needs to come from sources that can be ramped up or down depending on load conditions (Hydro, Nuclear, Coal, Oil).

Therefore in order for solar or wind to supply more than 50% of electricity it also needs a good amount of energy storage, which adds to the total cost.

In fact this even more interesting article in The Economist seems to suggest that costs are indeed likely to be higher.

Quoting from the article:

Pressure from governments forced it to strip out of its deliberations a table showing the link between greenhouse gases and national income, presumably because this made clear that middle-income countries such as China are the biggest contributors to new emissions. It also got rid of references to historical contributions, which show that rich countries bear a disproportionate responsibility.

• John Baez says:

Giampiero wrote:

There is an interesting exchange of posts on the fact that cost of climate mitigation is supposedly very low (0.06% of GDP).

While I agree with the fact that more growth doesn’t necessarily mean “more stuff”, I find hard to reconcile this finding with the “common sense” notion that reaching an 80% target for energy (electrical only, i guess, but not sure) coming from low carbon supplies by 2050 (in just 35 years) must be a near-monumental achievement.

Yes—what’s going on here?

This is something worth understanding. It seems this conflict is built into the IPCC reports. In your first link there, Joe Romm says this:

Now you might think it would be a no-brainer that humanity would be willing to pay a very high cost to avoid such catastrophes and achieve the low emission “2°C” (3.6°F) pathway in the left figure above (RCP2.6 — which is a total greenhouse gas level in 2100 equivalent to roughly 450 parts per million of CO2). But the third report finds that the “cost” of doing so is to reduce the median annual growth of consumption over this century by a mere 0.06%.

You read that right, the annual growth loss to preserve a livable climate is 0.06% — and that’s “relative to annualized consumption growth in the baseline that is between 1.6% and 3% per year.” So we’re talking annual growth of, say 2.24% rather than 2.30% to save billions and billions of people from needless suffering for decades if not centuries. As always, every word of the report was signed off on by every major government in the world.

Global mitigation costs for stabilization at a level “likely” to stay below 2°C (3.6°F). Cost estimates shown in this table do not consider the benefits of reduced climate change as well as co-benefits of mitigation. The green columns show the consumption loss in the years 2030, 2050, and 2100 relative to a baseline development without climate policy. The light green column shows that the annualized consumption growth reduction over the century is 0.06%. Source: IPCC 2014.

So, that’s an annual growth loss of 0.06%. That sounds small. I should try to translate it into dollars spent—then it will sound bigger. But later in his same post, he points out that it will require this seemingly enormous task:

The IPCC notes, “In the majority of low stabilization scenarios, the share of low carbon electricity supply [renewable energy, nuclear, and carbon capture] increases from the current share of approximately 30% to more than 80% by 2050.” That kind of rapid growth in near-zero-carbon energy over the next 3 1/2 decades leaves very little room for any new fossil fuel generation.

I trust him to be correctly reporting what the IPCC says, but that just means I need to dig into the report and see if it makes sense. Can we really increase the share of low-carbon electricity from 30% to 80% in 36 years—and do a lot of other stuff, too!—at such a low cost as they’re saying?

Where did someone actually crunch the numbers?

• John Baez says:

Joe Romm wrote:

The IPCC notes, “In the majority of low stabilization scenarios, the share of low carbon electricity supply [renewable energy, nuclear, and carbon capture] increases from the current share of approximately 30% to more than 80% by 2050.” That kind of rapid growth in near-zero-carbon energy over the next 3 1/2 decades leaves very little room for any new fossil fuel generation.

I wrote:

I trust him to be correctly reporting what the IPCC says…

Well…. I’m sure he’s not making up that quote, but look what Steve said in Part 7! It paints a more dramatic picture of what the IPCC report says:

Only one of the four future scenarios (RCP2.6) shows us staying below the UN’s commitment to no more than 2 °C of warming. In RCP2.6, emissions peak soon (within the next decade or so), and then drop fast, under a stronger emissions reduction policy than anyone has ever proposed in international negotiations to date. For example, the post-Kyoto negotiations have looked at targets in the region of 80% reductions in emissions over say a 50 year period. In contrast, the chart below shows something far more ambitious: we need more than 100% emissions reductions. We need to become carbon negative:

(Figure 12.46) a) CO2 emissions for the RCP2.6 scenario (black) and three illustrative modified emission pathways leading to the same warming, b) global temperature change relative to preindustrial for the pathways shown in panel (a).

The graph on the left shows four possible CO2 emissions paths that would all deliver the RCP2.6 scenario, while the graph on the right shows the resulting temperature change for these four. They all give similar results for temperature change, but differ in how we go about reducing emissions. For example, the black curve shows CO2 emissions peaking by 2020 at a level barely above today’s, and then dropping steadily until emissions are below zero by about 2070. Two other curves show what happens if emissions peak higher and later: the eventual reduction has to happen much more steeply. The blue dashed curve offers an implausible scenario, so consider it a thought experiment: if we held emissions constant at today’s level, we have exactly 30 years left before we would have to instantly reduce emissions to zero forever.

How come the IPCC says we can do this with only 0.06% less annual economic growth???

• Assuming a 3% annual growth from 2015 to 2100 leads to a multiplication factor of (1+3/100)^(2100-2015) = 12.34.

Removing 0.06% over the same period leads to (1+(3-0.06)/100)^(2100-2015) = 11.74.

Since global GDP is currently 85 T\$, the difference is 85*(12.34-11.74), which is exactly 51 T\$ (using 2100 dollars).

Assuming it makes sense to discount to the present at the same average rate, the present (2015) value of 51 T\$ in 2100 is around 4.3 T\$, which is not a lot.

Perhaps the real issue is who is going to bear this cost (and when is that meant to happen) especially if that requires a big initial investment (which could be if nuclear plays a substantial part).

• John Baez says:

Thanks for doing this calculation! I still need to find out how this 0.06% annual loss of growth figure was computed! It’s discussed on page of the final draft of the Summary for Policymakers of the Working Group 3 AR5 report. But I think we need to wait until the whole WG3 report comes out to dig into the details.

The summary says:

Estimates of the aggregate economic costs of mitigation vary widely and are highly sensitive to model design and assumptions as well as the specification of scenarios, including the characterization of technologies and the timing
of mitigation (high confidence).

Scenarios in which all countries of the world begin mitigation immediately, there is a single global carbon price, and all key technologies are available, have been used as a cost‐effective benchmark for estimating macroeconomic mitigation costs (Table SPM.2, green segments). Under these assumptions, mitigation scenarios that reach atmospheric concentrations of about 450ppm CO2eq by 2100 entail losses inglobal consumption—not including benefits of reduced climate change as well as co-benefits and adverse side‐effects of mitigation—of 1% to 4% (median: 1.7%) in 2030, 2% to 6% (median: 3.4%) in 2050, and 3% to 11% (median: 4.8%) in 2100 relative to consumption in baseline scenarios that grows anywhere from 300% to more than 900% over the century. These numbers correspond to an annualized reduction of consumption growth by 0.04 to 0.14 (median: 0.06) percentage points over the century relative to annualized consumption growth in the baseline that is between 1.6% and 3% per year.

So, one reason this 0.06% figure is so low it’s that it’s assuming a ‘world without friction’: all countries of the world begin mitigation immediately, there is a single global carbon price, and all key technologies are available!

• I think that part of the problem is that “loss of growth” is the wrong way to think about costs. Remember that GDP is a measure of the flow of money through the economy. If all the governments of the world invest like crazy in clean energy infrastructure, it will create amazing economic growth (remember that GDP includes government spending as well as private sector) – it’s like putting the world on a war footing and maximizing industrial output of things like solar panels, wind turbines, electric vehicles, etc. That’s likely to create an economic boom unlike anything we’ve ever seen.

On the other hand, all the economics models used for this analysis are useless in such a world. They assume a market-driven capitalist economy, with growth built as a basic assumption. At the same time that we do this massive investment in clean energy infrastructure, we have to dismantle the consumer economy and replace it with one that does not rely on economic growth, because the only way to feed continuing growth in the long term is via growth in consumption. And indefinite growth in consumption is not possible on a finite planet. The best analysis of the economics of this is probably Tim Jackson’s work.

• Steve wrote:

If all the governments of the world invest like crazy in clean energy infrastructure, it will create amazing economic growth

I think this is a very good point, especially in this low-growth high-unemployment economic climate. I tend to agree with this view, even though i don’t think that war-like massive government investments are going to happen, unfortunately.

On the other hand, all the economics models used for this analysis are useless in such a world.

I’d be curious to actually have a look at the model they used. They have probably assumed that these energy investments will necessarily “crowd out” other investments and possibly better (more efficient) use of resources, therefore leading to a “multiplier” on these investments less than one.

But the reality is that it’s hard to model the impact of these investments trough the economy. This article says that:

Germany and Spain have gone further than most in using public subsidies to boost the share of renewable energy (though to nothing like 80%) and their bills have been enormous: 0.6% of GDP a year in Germany and 0.8% in Spain. The costs of emission-reduction measures have routinely proved much higher than expected.

Moreover, the assumptions used to calculate long-term costs in the models are, as Robert Pindyck of the National Bureau of Economic Research, in Cambridge, Massachusetts, put it, “completely made up”. In such circumstances, estimates of the costs and benefits of climate change in 2100 are next to useless.

I want to read the article on prosperity without growth, i think it’s super-interesting. However i don’t agree with you when you say that:

… we have to dismantle the consumer economy and replace it with one that does not rely on economic growth, because the only way to feed continuing growth in the long term is via growth in consumption.

First, growth in consumption does not have to mean consuming more material stuff, (think about services for example).

You can still make the case that service consumption is limited (e.g. by our time or attention) and it is anyway linked to somehow using energy (and i would probably agree), but the case is not really clear-cut.

Also if by “consumer economy” you mean an economy in which consumer spending plays a big role (e.g. US) then such an economy does not really rely on growth (an “investment” economy like China does). Perhaps you are advocating an economy in which the majority of spending comes for the government, which to some extent might be a good idea.

But in any case it’s not clear to me that we “have to” “dismantle” the current economic system (and replace it with something new/different) in order to address climate change. Besides, changing the economic system, is another huge challenge in itself, and taking on too many challenges at the same time might very well be a receipt for failure on all fronts.

• Something related:

http://www.newscientist.com/article/dn25846-stopping-harmful-climate-change-is-surprisingly-cheap.html

To avoid dangerous climate change, the world needs to boost spending on green energy by \$1 trillion a year. That sounds scarily large, but we could cover a lot of it using the subsidies currently handed to fossil fuels.

5. and all key technologies are available

I am not sure what that means exactly, but i’d say that the key technologies (dependable sources of energy that cost less than extract and burn fossil fuels) are clearly not available. Not even in the most technologically advanced countries.

• John Baez says:

I hope they are restricting the phrase ‘key technologies’ to technologies that actually exist: the ability to teleport CO2 molecules to Mars would be great, but…

Anyway, I’ll need to read the detailed report when it comes out.

6. John Baez says:

I have a new project, which is to understand why the economist Richard Tole, in this paper:

• Richard Tole, The economic effects of climate change, Journal of Economic Perspectives, 23 (2009) 29–51.

estimates that economic models predict that global warming will be beneficial to the GDP until it reaches 2.8° C above pre-industrial levels, at which point the harm will start to outweigh the benefits. This is in contrast to the IPCC recommendation to hold global warming below 2 °C.

The discussion I had with David Friedman is the reason I got interested in this.

7. I think this short blog post is very relevant to the discussion we had in the thread above:

http://krugman.blogs.nytimes.com/2014/05/19/demography-and-the-bicycle-effect/

my take is that at the end of the day we have to pick our own poison, (and we already know who is going make the decision).

8. […] Easterbrook S (2019) Novo Relatório do IPCC (Parte 6). Azimute. https://johncarlosbaez.wordpress.com/2014/04/16/what-does-the-new-ipcc-report-say-about-climate-chan&#8230; […]

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