When the Old Man asked what the odds were, Tamino very helpfully put a scientific gloss on answers which were no great surprise at the cave. To help you if you missed it, here are some baseline numbers for the odds of some climate impacts by 2040:
- 65% chance of temperatures increasing by more than 0.5C from now.
- 87% cumulative chance that the increase will be greater than 0.3C.
- 90% chance that sea level rise will be greater than 10cm, 50% that it will be between 10-20cm.
- 85% cumulative chance that Arctic sea ice extent will decline by more than 10%.
- No clear indication that tropical cyclone activity will reduce, increase or stay the same. (it does change if you use different rulers to measure it).
- 60% cumulative chance that life in the oceans will decline by up to 25%.
- 60% cumulative chance that global forest area will decline by more than 10%.
Looked at as a package, the picture is not encouraging. These are not dramatic exaggerations or unrealistic expectations. You may feel that some of these things are more likely to come about than others. On the other hand, you may recognise that the odds are good that most or all of these things will happen in tandem with one another, as they all relate to how the change in climate is changing the systems within which our civilization functions.
Now you can turn those odds around; odds against a temperature rise of >0.3C, a sea level rise of >10cm, and an Arctic sea ice loss of >10%, are about 1 in 10; not a great prognosis.
There are other climate impacts which can be considered as important, too, though the odds are rather harder to calculate for some of them; once again, the marker is set at 2040: What are the odds of the following:
- the Palmer Drought Severity Index (the ‘standard’ measure of drought occurrence) showing an increase in globally drought-affected areas of more than 10%?
- ocean acidity levels (pH) increasing by more than10%?
- the number of persons displaced by climate impacts or development related to climate increasing by more than 20%?
- the economic cost of coastal damage to life and property increasing (at net present values) by more than 20%?
The Old Man would guess that the odds for each of these is probably comparable to the previous set of impacts; I await discussion with bated breath.
What is the point of bringing these things up? How significant are changes to individual measures at these relatively modest levels? It could be argued that a 10% increase in drought-afflicted areas is not ‘catastrophic’ (unless you depend on the land for a livelihood) in a global picture. The same argument could be made for any one of these impacts; in itself, no one impact need necessarily be seen to be a ‘disaster’.
But we aren’t talking about one, or even a couple, of highly likely climate impacts by 2040; we’re considering all of them, happening at the same time, together. And there’s no consideration of feedback effects, ‘knock-ons’ or, save us all, some or all of these impacts being worse than this ‘gentle change’ scenario suggests.
Two fairly obvious thoughts spring to mind. Firstly, the environmental and human consequences of such a collective transformation in the global ‘system’ will intermingle; the ‘big picture’ is far worse than the sum of the nasty little parts. It’s as if the planet has been run over by a large truck. The injuries sustained are none of them, individually, going to kill the patient, but the compound effect of all that trauma makes the odds of pulling through a whole lot lower.
The second thought is that the Economic A&E department is going to struggle to cope with all this damage. The recent reports on the economic costs of mitigation (or adaptation) have tended towards considering these in a 100-year timeframe. The argument here is that the likely compounded cost of climate change by 2040, even with some mitigation, is more than enough to justify immediate action to reduce emissions, and, beyond this, is of a far greater value than the Stern, IPCC or other assessments have allowed for.
The break-even line should be measured at 2040, not 2100. The chances are very good that nothing we can do about mitigation will prevent at least some of these impacts and costs by this time. But they are also quite good that we could see some real benefits from immediate action soon after this. As this is likely to coincide with the effective termination of readily-accessible oil and gas reserves (at current usage rates), there is a benefit for energy providers and resource managers, who can set a target deadline for the implementation of an 80% transfer of primary energy and fuel sources. It is also within the lifetimes of a large proportion of the world’s population. It is more real and more relevant.
So now it is your turn; the goalposts are going to move towards us, to 2040. What do we need to do, what policies need to be adopted, what messages need to be transmitted, to reach a state of the global human/environmental/climate system in 2040 which is, at the very least, no longer out of control?
Be loved.
Old man in a cave 
6 comments
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May 24, 2007 at 1:14 am
Hank Roberts
These folks have been making sense on concerns over this time scale:
Click to access InconvenientTruth2.pdf
Author Paul Baer has participated in some climate blog threads, I recall, about the probability range (probability distribution function). A while back, some of the climate scientists were dubious about the risk of exceeding the IPCC worst case. I gather that’s now happening.
See p. 4:
-quote———–
What, then, would it take to hold the 2°C line? Given the slow progress to date, the only honest answer is “a heroic effort.” To see just how heroic it would have to be, consider the three progressively more ambitious emissions trajectories shown in the figure [see the pdf file].
Attend, in particular, to the probability ranges, which, following the current treatment of the key scientific uncertainties6, estimate the risk that each trajectory would lead to a warming greater than 2ºC degrees.
The 2ºC Crash Program, its Alternatives and its Odds
Emissions pathways for three scenarios – a “2ºC Crash Program” and typical pathways for 450 ppm or 550 ppm CO2 stabilization – along with the risk of exceeding the 2ºC threshold (as calculated by Baer and Mastrandrea 2006).
The most stringent of these trajectories, which I’ll call the “2°C Crash Program,” is heroic indeed. It has emissions peaking in 2010 and then dropping by a resolute 5% per year, leading to peak carbon-dioxide concentrations around 410 parts per million. Note then, that even with this almost inconceivable effort, we’d still be exposed to an alarming 9-26% risk of exceeding 2ºC degrees.7
Note, too, what this analysis tells us about today’s conception of political realism. For the 450 ppm CO2 trajectory (which was, until very recently, cited by most large U.S. climate organizations as being both safe and achievable) is likely to far overshoot 2ºC.
—– end quote———
May 24, 2007 at 2:17 am
Simon D
I applaud the effort to express things this way. It is, however, tough to really work out odds from the IPCC since the SRES scenarios are intended to be independent, different possible futures, not a defined range for estimating probabilities. In reality, say, there could be a 60% of the world landing in one of the four main scenarios, rather than a 25% chance.
Nonetheless, it’s worth trying to articulate the evidence in this manner. If you’re speaking of 2040, most research is showing that without some adaptation by corals, coral bleaching events will be occuring every one or two years across much of the tropics by that time.
May 24, 2007 at 11:13 am
fergusbrown
Welcome to you both, Hank, Simon, thank you for commenting.
EcoEquity is indeed an interesting site for it’s content, but I don’t think they have a weblog, so I have already asked Paul Baer to provide something for the Cave: his answer suggested he might. Tom Athanasiou is the ‘other half’ of the organisation, and he already posts as a regular on Grist (in blogroll).
To clarify, when the quotation refers to ‘the 2C pathway’, are we to understand that Paul is referring to a total warming of 2C, eventually, from pre-industrial average temperatures? If this is the case, how do we relate this to the 2040 target date? I’d guess that, if +0.5C is close to unavoidable as things stand, making for a total of +1.5C from the pre-industrial, then 2C by the end of the century is only avoidable if there are no emissions at all after 2040-50, and some effective geoengineering solution has been put in place to artificially suppress temperature rises; perhaps something like the ‘Bower boats’ that have been discussed on the Google Globalchange group page.
I’d be inclined to agree with those climate scientists who see a rise of 3C as the more realistic probable net temperature gain, possibly later this century or in the next. But we can’t rule out the possibility of this kind of rise by 2080 either, if mitigation policies don’t address the atmospheric concentration of greenhouse gases effectively.
Simon: you may have guessed that the numerical expression of probabilities has used material beyond the IPCC AR4 analysis, from the journals, as well as the IPCC material. Both Tamino and I are reading similar material, which is not limited by the need to conform to the IPCC’s ‘rules’; as a result, most of them are much more recent than the papers on which the AR4 analysis is based.
Another reason why 2040 is a useful target date is that the range of different effects from different SRES scenarios is much smaller at this timescale; the relevance of their development scenarios really hits in during the second half of the 21st century and beyond. I’ll think about the SRES and the odds of each pathway being acheivable later; I’d guess that at least one scenario can be all but eliminated already.
Do you know what the effect of the coral bleaching will be? How will a loss of this component of the ocean system impact on sea life, and further, on human society or coastal security? You’re a Princeton man (yes, I’m impressed); any thoughts?
Be loved.
May 27, 2007 at 3:51 pm
inel
Hello again, fergus!
Did you see today’s Times article?
I know this is not exactly what your post was aiming at, but I thought the idea of betting on green markets is worth discussing from an ethical and philosophical point of view, as well as economics. I am tossing this over in your direction, as I am not well-versed in any of these areas, but you could be the very man for the job of commenting on this whole business of making money out of climate change.
June 2, 2007 at 9:56 am
fergusbrown
Thanks for the heads-up, Inel; I’ll be thinking about this during the morning as I catch up with the blogs and the news and prepare a comment for the day. it reveals an important underlying attitude to all matters to do with the future which needs raising.
Regards,
June 3, 2007 at 4:01 pm
inel
Welcome back, fergus.
Nick Davies wrote another note in yesterday’s Guardian which makes for some unpleasant reading. Good for him for revealing it. In my simplistic interpretation, it boils down to a case of gambling on the environment, with gamblers winning, and the environment losing.
Truth about Kyoto: huge profits, little carbon saved
These stories make me feel sick. It is hard enough getting valid attention and changes of attitude in a good direction, let alone having to deal with people manipulating figures in order to benefit as climate profiteers. We urgently need economic goals to align with what’s best for the environment. Period.