Comments on: Stern report 3: sensitivities, sceptics, and Doomsday

By: Eli Rabett

Eli Rabett — Mon, 27 Nov 2006 23:55:12 +0000

You cannot have thermal runaway on earth because the top of the atmosphere is constrained to be below the boiling point of water. This is because we are that much further from the sun. Water vapor will always condense out and fall back to earth at some level of the atmosphere. Thus boiling off water vapor, which is what messed up Venus, is not allowed. It can get plenty unpleasant here tho.

By: Valuethinker

Valuethinker — Sat, 18 Nov 2006 15:52:31 +0000

Sally
The report looks into the CO2/GDP ratio in some detail.
CO2 emission rises with GDP at a fairly constant rate *but*
there are distinct structural shifts at certain levels of GDP/ head.
one is at about $5000 per head, and another at about $25000 per head.
When countries cross those lines, further GDP growth tends to produce markedly less CO2 emission (per unit of growth) than previously.
The hypothesis of that Stern Report is that we can bring forward those points of structural reduction by better technology and by a system of carbon permits.
It’s worth remembering that if the world economy keeps growing at the rate it has done since 1950 (2.2% real pa) then in 2050 it will be 2.7 times the current level, and in 2100 7.7 times.
If it keeps growing at the post 1990 rate (2.9% real) it will be 3.5 times the current level in 2050, and 14.7 times the current level in 2100.
That underlines a couple of points:
- spending 1%, or even 5%, of that GDP on CO2 emission control is not going to be an unbearable expense
- the scale of the mountain ahead of us to climb, in terms of reducing CO2 emission relative to GDP
We have many, but not all, of the technological and economic building blocks to do the latter.
The fact that CO2 emitted *now* will affect the climate 100 years from now, underlines that we have to get *moving*, to stand any chance of preventing the more severe scenarios of global climate change.
We are *now* deciding the climate our grandchildren and great grandchildren will face.

By: Valuethinker

Valuethinker — Sat, 18 Nov 2006 15:33:08 +0000

Brett
We’ve argued the toss on geo-engineering before.
1. I did some back of the envelope calculations about man-made efforts to change the planet’s albedo. You get to enormous numbers: just covering 10% of the surface of the planet with tinfoil is a huge number.
It would be much cheaper simply to replace all our coal-fired stations with IGCCs and sequester the CO2 output off the syngas synthesisers.
2. SO2 injection into the atmosphere is only a short term solution: SO2 lasts weeks in the atmosphere, but CO2 over 100 years. And the acid rain could wind up killing more plant life.
3. I don’t know what other ‘geoengineered’ solutions you were thinking of but the generic problem with this class of ‘solutions’ is that injecting excess CO2 into the atmosphere and then injecting *something else* to offset the heating absorption effect is *not* the same thing as restoring the atmosphere to its original condition.
4. we might be able to do something with genetically engineered algae. But an algae bloom like that could kill all other sea life. And the ocean also needs nutrients (there were experiments with salting the ocean with iron pyrites, but they weren’t successful).
So if we get desparate we might try it, but it has big risks and problems, and we certainly don’t know how to do it now.
5. I’ll put orbital shades into the science fiction realm. At current costs per pound into orbit, we can’t do it. And if we could do it, we should go whole hog and have solar power satellites.

By: Valuethinker

Valuethinker — Sat, 18 Nov 2006 15:26:25 +0000

So to sum up, we have a number of ‘tipping points’, arising from the fact that what we are doing is geologically unprecedented (almost), pouring CO2 into the atmosphere:
- rainforest destruction — rainforest turns from a sequester of CO2 into a source (I’ve heard estimates of as little as 3 years of drought, certainly Australia is having the ’1 in 1000 year drought’)
- permafrost accelerated melt and methane release*
- decline in the earth’s albedo due to alpine ice melt and Arctic warming
- sudden climate change due to interruption of the THC
- Permian Extinction effects as described: the ‘redline’ is 1000ppm, but we don’t know at what point the positive feedback effects of global heating kick in (and then we can do, literally, nothing to stop it)
- (one I didn’t mention) – dying of oceanic life due to increased oceanic acidification. Already small hard-shelled creatures are dying off, because they cannot form their shells in the higher acidity. Kill enough ocean life, and the power of it to sequester CO2 is lost.
This is a new threat, and I don’t know much about it, but neither, I think, do the ocean biologists. But indeed, the ph of the ocean is changing.
* my calculation is off due to confusing Carbon and CO2 (1 tonne emitted carbon is 3.667 tonnes emitted CO2). 1 tonne CH4 (methane) = 20 tonnes CO2 in greenhouse gas effects = 5.45 tonnes Carbon release. Of course, CH4 decays in the atmosphere relatively quickly, combining with oxygen to produce CO2 as a residual gas.
The reality is we don’t know what kind of planet we will have, and what kind of civilization, if the weather warms more than 5 degrees centigrade.
Would this be the end of life on earth? I doubt it. Algae would evolve that would adapt to the higher CO2 levels, and eventually, perhaps over thousands of years, reduce them– there is precedent. James Lovelock says that a couple of hundred million of us will evolve a new, nuclear powered civilisation around the shores of a Meditteranean-like Arctic ocean.
What chance does one need of effects like the Permian Extinction to justify radical action? 1%? half a per cent? 0.1 per cent?
The bathtub metaphor is apt. We are already committed to a much warmer planet– the CO2 emitted up to now will last up to 100 years in the atmosphere. We have little or no control over the next 2 degrees centigrade of heating.
I know some geophysicists who think we have already passed the tipping point.

By: Valuethinker

Valuethinker — Sat, 18 Nov 2006 15:12:53 +0000

2 (cont’d) — we emit 7 Gt of carbon pa, and estimated sequestration is half that. So a 180mt release pa of methane is going to do as much damage, again, as all our CO2 release.
3. the Arctic heats up because as the snow cover lasts less time and there is less of it, there is less albedo (solar reflectivity). Again a positive feedback loop is created. The temperature swing in the Arctic is going to be much bigger than the 2 to 5 degree centigrade swing at the equator.
The above 3 are the key ‘tipping points’ *that we know about*. But see 5.
4. there is the Atlantic thermo-haline circulation (THC). This is also known as the Gulf Stream and the Atlantic Conveyor. We don’t know what happens if increased icewater release interrupts that.
What we do know is that the earth’s climate goes through long stable periods, and then occasional sudden ‘flippings’ or ‘pulsings’.
The effect of 4 might be to cool Europe dramatically, or it might not.
5. The Permian Extinction is the poster child of the rapid CO2 rise. The result was the extinction of 90% of animal life on the planet.
http://www.sciam.com/article.cfm?articleID=00037A5D-A938-150E-A93883414B7F0000&sc=I100322
(cont’d next post)

By: sally

sally — Fri, 17 Nov 2006 21:32:19 +0000

Within the same long time lag we are now looking at, have we assumed the continuing same rate of CO2 contributions by GDP?
Then how do we spend our money? More to hedge the “runaway warming”, or reduce the growth rate of Co2 contributed by GDP(or production)?
Can we control the “runnaway warming”? If we can, will it reduce the rate of CO2 growth rate contributed by GDP(or production)?
If the latter is preferred, how much confidence should we put into the past Co2 growth rate?

By: Brett Bellmore

Brett Bellmore — Fri, 17 Nov 2006 18:21:45 +0000

To be fair, the level of CO2 in the atmosphere has been generally declining at the same time that the Sun’s output has been *rising*, so it’s not totally implausible that we could see thermal runaway at a CO2 level which the planet endured in the *very distant* past.
However…
“Once we pass the ‘tipping point’ then nothing we do will halt the inexorable rise of CO2 in the atmosphere.”
Got a rather constricted view of what we’re capable of doing if we really have to, don’t you?

By: Jane Galt

Jane Galt — Fri, 17 Nov 2006 16:44:27 +0000

Valuethinker, that makes no sense. The planet started off with a lot of carbon dioxide in the air; it’s been progressively declining since the invetion of photosynthesis. We’re putting some of the carbon, not all of it, that used to be there back. By what mechanism doesn’t putting the carbon dioxide that used to be in the atmosphere, back into it, suddenly trigger a runaway effect?

By: Valuethinker

Valuethinker — Fri, 17 Nov 2006 16:35:55 +0000

Jane
I posted a long answer, complete with cites. It hasn’t appeared, not sure why.
The short answer is it took millions of years to sequester all the carbon in coal, oil and natural gas.
We are releasing that, plus other greenhouse gases such as CFC, plus CO2 from biomass, in the space of less than 350 years, 1750 to 2150 roughly.
In fact, it is much worse than that: something like half that CO2 release has been since 1945.
The effect is like overfilling a bathtub. Carbon dioxide released sits in the atmosphere for 100 years.
The planet has a capacity to absorb c. 4.5bn tonnes of carbon a year.
We are emitting 7bn tonnes carbon pa, plus another 2bn tpa from land use changes, deforestation etc.
This *could* become a runaway process, if there is massive methane release from permafrost melt, if there is massive die-off of the rainforests due to drought.
It is also the case that plants become less efficient removers of CO2 as CO2 concentrations rise.
Once we pass the ‘tipping point’ then nothing we do will halt the inexorable rise of CO2 in the atmosphere.
We don’t know what that tipping point is, but some scientists think it could be as low as 550ppm (v. 380ppm now) or even lower. At current growth rates of CO2 emission growth, that is less than 75 years away.

By: Bruce Wilder

Bruce Wilder — Fri, 17 Nov 2006 16:27:23 +0000

I’m sorry, Dano, but your point is very unclear to me. What is the “only” option?

By: Valuethinker

Valuethinker — Fri, 17 Nov 2006 07:25:52 +0000

Hmmm.
My comments aren’t appearing. I twice drafted a long reply to Jane Galt, which hasn’t appeared.
James, is there a problem?
(drop the ‘at’ in email if you wish to email me)

By: Dano

Dano — Fri, 17 Nov 2006 00:44:26 +0000

Bruce,
The pace-of-change you refer to is known in ecology as ‘rate of change’ and the threshold is the ‘tipping point, best thought of as a sigmoid curve (sorry no HTML here to enhance my comments).
Ecosystems that resist catastrophe with stress are ‘resilient’. The issue is that we cannot control resilience with our current technology, so managing ecosystems to the tipping point is a poor strategy due to our current knowledge; managing this way in hopes of technology coming up with a solution may best be termed as crazy.
Thus, your point of slow pace-of-change (wrt ‘emissions’) is, with our current knowledge set, the best [only] option in my view. And what I think James is getting at in his middle graph.
Best,
D

By: Bruce Wilder

Bruce Wilder — Thu, 16 Nov 2006 22:00:34 +0000

I appreciate the effort to think through the issue, on the level of good democratic citizen.
I don’t know if I can express my concern clearly enough, but I’ll give it a go:
I get that the time lags between atmospheric chemistry and climate are long, but doesn’t that make the critical policy variable either a critical threshold or a sustainable pace of change?
Is the aim of policy going to be to slow the rate of increase in emissions to a level consonant with a “safe” or sustainable pace of change? Or, is the objective of policy going to be to avoid some expected threshold, the risks of which are viewed as being too extreme?
What I get, through the filter of journalism, is that the wide band of uncertainty on target (Y2100) values actually reflect a high degree of certainty that the pace-of-change cannot be usefully controlled, without identifying a companion threshold limit.
Pace-of-change, by itself, imposes costs, which at higher rates of change, accelerate. Resources expended in amelioration or adjustment costs can be balanced against reducing the pace-of-change, by reducing the rate at which additional carbon emissions change the atmospheric and oceanic chemistry.
Pace-of-change, however, can not be considered in isolation from threshold values. Above certain threshold values, the pace of change may not be controllable. That there is a substantial risk that the pace of change might become uncontrollable is the real meaning of the fairly wide range of Y2100 target values.
A threshold, beyond which pace-of-change becomes uncontrollable, would seem critical to identify. Beyond that threshold, policy would be useless. Not only would the adjustment/amelioration costs accelerate, but the economic foundation providing the resources to meet those costs might be deteriorating uncontrollably. And, there would no longer be a policy option to restrain pace-of-change by restraining carbon emissions.
The brakes must be applied to carbon emissions, with an eye toward not crossing that critical threshold. The threshold, not estimates of Y2100 conditions, ought to be the objective of policy-oriented analysis.

By: No Nym

No Nym — Thu, 16 Nov 2006 15:20:10 +0000

Oops. The journal for that cite is:
ScientificWorldJournal. 3:357-411.

By: No Nym

No Nym — Thu, 16 Nov 2006 15:18:26 +0000

You should refer all skeptics to this paper:
Keller, CF (2003) Global warming: the balance of evidence and its policy implications. A review of the current state-of-the-controversy. 3:357-411.
It considers all the data, their sources, alternative explanations, etc. Overall a good review.
Even the most skeptical models, relying on sunspot cycles and so forth, have the result that 50-70% of the warming is due to carbon emissions.

By: Jane Galt

Jane Galt — Thu, 16 Nov 2006 03:03:26 +0000

While I am a firm believer in global warming, a physicist friend pointed out the ridiculousness of the “runaway warming” scenario. We’re putting the carbon back into the air that was there during the Jurassic; that’s where the plants that ultimately turned into fossil fuels got it. The planet has supported life capably for 4 billion years; adding back the carbon that was once removed is unlikely to change that, though it may have all sorts of adverse effects on Africans and those living below sea level.
Venus is a lot closer to the sun, and has all sorts of other greenhouse gasses floating around in there; there is absolutely no reason to think it will happen here. One can’t rule it out, but one also can’t rule out the snowball earth scenario, or the not entirely unlikely possibility that our current carbon output is staving off the return of another ice age.