Robert Laughlin article, not all bad

At this late stage I just got around to reading the controversial article by Robert Laughlin, Nobel-prize-winning physicist, "What the Earth Knows." Large parts seem totally uncontroversial to me:

Carbon dioxide from the human burning of fossil fuel is building up in the atmosphere at a frightening pace, enough to double the present concentration in a century. This buildup has the potential to raise average temperatures on the earth several degrees centigrade, enough to modify the weather and accelerate melting of the polar ice sheets.

The IPCC couldn't say it better. And he understands the distinction, which I discussed here, between what is a big deal for humans and a big deal in terms of the time scale of the earth.

It's not at all controversial to say AGW will be a tiny ripple in geologic history: global thermonuclear war would be a tiny ripple in geologic history. That's a function of the vastness of geologic time; on a human timescale these things are quite a bit more important.

There are a couple of silly ideas, one, which has been discussed at length in the blogosphere, being the idea that there is "no solid scientific support" for our ideas about the causes of past climate change. That mistake could be a function of ignorance of the subject, or it could be a function of a physicist's unrealistic idea of what constitutes "solid scientific support" outside his own field.

Then, after seeming to comprehend so well the difference between human and geologic time, he goes off the rails and equates them:

The geologic record suggests that climate ought not to concern us too much when we’re gazing into the energy future, not because it’s unimportant, but because it’s beyond our power to control.

No. This is like saying that because the earth is sometime struck by giant meteors, it's pointless to try and avoid nuclear war. Human-caused is different in a very practical sense from natural changes, because natural changes happen over geologic time: that is, from a human perspective, they occur hugely infrequently and usually very slowly. They occur so infrequently, in the earth's 4.5 billion-year history, that the chances of the next thousand years seeing even one of these natural shifts is tiny.

Whereas human-triggered changes occur with blinding swiftness by the earth's standards and, by logical necessity, humans are always around to suffer the consequences.

Open Mind calls it

I have to give a shout out to Tamino at Open Mind, who call the low point of Arctic ice within 1% of the true value. Amazing! He predicted 4.78 million km^2. The actual value was 4.81 million km^2.

Needless to say, he kicked denier butt on this one -- Anthony Watts and Steve Goddard, whose frequent posts on the state of the Arctic brightened our summer, missed the mark by 960,000 km^2 (High or low? Do you have to ask?)

Besides demonstrating yet again the value of recognizing the reality of global warming when making predictions about the physical world, what's notable about Tamino's eerile accurate prediction is that he generated it by plotting an exponential decline in the Arctic ice cover -- that is, in popular terms, a death spiral.

Between the science and a hard place, Part Two: Confidence and Risk

As you sit in what is hopefully a comfy chair, blissfully consuming this fine, robustly flavored, 100% complimentary content, have a moment's sympathy for the lot of the climate blogger. Many are his (or her) woes.

Fer instance, I want to talk to you today about the Scylla and Charybdis of lukewarmism, confidence intervals and risk. I would normally pursue this much as I did in the last installment, by plugging in some lukewarmist assumptions and discussing the results. But the trouble with this, as we saw in Part One, is that even the most conservative lukewarmist predictions imply equilibrium warming greater than 2 degrees C – a condition not seen for millions of years, which climate scientists predict will lead to disaster. In order to talk about the problems of confidence intervals and risk, though, we need a projection that doesn't definitely lead to disaster.

My solution is to pull from the AR4 absolutely the lowest-warming model, based on the lower bound of the 95% confidence interval for the lowest-emission scenario family, B1. This family is described as follows:

The B1 scenarios are of a world more integrated, and more ecologically friendly. The B1 scenarios are characterized by:
• Rapid economic growth as in A1, but with rapid changes towards a service and information economy.
• Population rising to 9 billion in 2050 and then declining as in A1.
• Reductions in material intensity and the introduction of clean and resource efficient technologies.
• An emphasis on global solutions to economic, social and environmental stability.

This is a totally unjustifiable procedure on a couple of levels. Obviously at the moment we are not making anything that could be described as rapid progress towards an "integrated . . . ecologically friendly world." Put that to one side. You also cannot simply take the lowest bound of the lowest temperature rise scenario and call that your estimate; that's cherry-picking of the worst kind. But this is the only way to get an estimate this low, so . . . I'm going to have to ask you to play along.

So say I'm a lukewarmer, and I think we're in for about 1.1C in warming over the next century. Add that to the 0.7C seen since the start of the industrial revolution, and you end up with 1.8C of warming – a princely 0.2C below our maximum safe-ish warming of 2C. Provide we do not care anything about what happens after 2100, as for example, in 2120 or 2130, we're golden.

Having ascended to these lofty height of assumption, we can finally deliver the coup de grace (the stress is causing me to mix my metaphors – who would be dealing out mercy killings on a mountaintop?) We have our lukewarmer, and they have their 1.1C by 2100. First question: What is your level of confidence in that projection? Let's look at some real-life estimates of climate sensitivity, based on actual data:

Royer, et al. (2007)[24] determined climate sensitivity within a major part of the Phanerozoic. The range of values—1.5 °C minimum, 2.8 °C best estimate, and 6.2 °C maximum—is, given various uncertainties, consistent with sensitivities of current climate models and with other determinations.http://en.wikipedia.org/wiki/Climate_sensitivity - cite_note-24

Annan and Hargreaves (2006)[22] presented an estimate that resulted from combining prior estimates based on analyses of paleoclimate, responses to volcanic eruptions, and the temperature change in response to forcings over the twentieth century. They also introduced a triad notation (L, C, H) to convey the probability distribution function (pdf) of the sensitivity, where the central value C indicates the maximum likelihood estimate in degrees Celsius and the outer values L and H represent the limits of the 95% confidence interval for a pdf, or 95% of the area under the curve for a likelihood function. In this notation their estimate of sensitivity was (1.7, 2.9, 4.9)°C.

Based on analysis of uncertainties in total forcing, in Antarctic cooling, and in the ratio of global to Antarctic cooling of the last glacial maximum relative to the present, Ganopolski and Schneider von Deimling (2008) infer a range of 1.3 to 6.8 °C for climate sensitivity determined by this approach.[12]

Andronova and Schlesinger (2001) found that the climate sensitivity could lie between 1 and 10°C, with a 54 percent likelihood that it lies outside the IPCC range.http://en.wikipedia.org/wiki/Climate_sensitivity - cite_note-15

The first thing you likely noticed about these calculations is that to continue to test lukewarmism we have really, really underestimated the magnitude of the warming expected in the 21st century. But the second thing you should notice is that the ranges -- the confidence intervals -- are really large. Climate sensitivity is a fiendishly difficult thing to pin down with precision, and most honest scientists come up with a range of 4-9 degrees C for the sensitivity that may be implied by any given data set or model. Those assimilating the results of many experiments and model runs can do substantially better, with recent estimates of 2.6-4.1C, a range of only 1.5C, or 2.6C if we reach down and include the unlikely possible of a sensitivity of 1.5C.

So the critical question then becomes: what is the lukewarmers' range? Consensus scientists estimate climate sensitivity at about 3C, but concede that it might be 1.5C, 4.5C or even higher (and very unlikely to be much lower). What range do lukewarmers think is plausible?

So far, to my knowledge, no self-identified lukewarmer has been persuaded to answer this question. They will find it difficult. Because they have positioned themselves as participants in the scientific debate, they can hardly claim 100% confidence in X climate sensitivity, no error bars. If they are reasonable, they have to accept they they are as fallible as the rest of the scientific community, and although they think the climate sensitivity is 1.5C (say) it might be 1.0C, or 2.0C, or even (gasp!) 3.0C (where the consensus puts it).

So even if they see 1.5C as the most likely number, they have to concede the possibility the number may be higher or lower. Emissions, too, may be higher or lower -- and so could the 2C estimate for disastrous climate change, which is just an estimate, be low or, what is more likely, high.

And this leads us to the problem of risk. What amount of risk will we accept in the next century that our civilization will be severely affected by global warming? Five percent? One percent? A tenth of one percent?

Put it another way: rapid cuts in emissions are estimated to cost between 1-3% of the GDP. Suppose there is a revolver to your head with a thousand cylinders (it's a big revolver). For a 3% raise, how many chambers are you willing to have loaded before your boss pulls the trigger? One? Maybe if you're hard up. One in a thousand's not a huge chance to take. Ten? Probably not, if you have anything to live for. A hundred? Never in a million years.

People differ in their appetites for risk, but I think most people would agree that a 1% risk of major climate disruptions like multi-meter sea level rise, massive droughts, mass extinctions, and millions of climate refugees, is around the upper limit of acceptable. And that's the end of lukewarmism (again). Any remotely reasonable estimate of climate sensitivity, even if centered on 1.5C or even lower, even if it gives you a central estimate of less than 2C, will carry with it the very significant chance that the real value is 2C or 2.5C or 3C. Traveling with it will be uncertainties about the rate of growth of emissions, and the possibility that less than 2C will get us to planetary disruptions like the rapid melting of most of the ice sheets or large-scale methane release.

Once you've acknowledged the greenhouse warming caused by CO2 and other greenhouse gases, even a ludicrously low estimate of climate sensitivity will not save you from the iron logic of risk assessment: "maybe not" and even "probably not" are unacceptable for the kind of impacts we're talking about. Even 1% is too high. But, absent a new data set allowing a much, much more exactly calculation of climate sensitivity than we have been able to provide to date, there is no way even the most Pollyanna estimates of climate sensitivity and future emissions can provide any acceptable level of assurance that "business as usual" is anything but a road to ruin.

Between the science and a hard place: The intellectual incoherence of lukewarmism. Part One: jimming the Overton window.

In recent years, the climate wars have witnessed the rise of a group of self-identified "lukewarmers," people who, to borrow Greg Easterbrook's self-description, believe that:

[G]lobal warming is scientifically confirmed but exaggerated as a threat; that greenhouse gas regulation is justified, but not an emergency need.

The first use of the term I have found was by David Smith, on "Watts Up With That" (a bit of foreshadowing, that):

I am a “lukewarmer” who thinks that the world is warmer than it would otherwise be due to anthropogenic gases (but doubts that the impact will be extreme).

Probably the most famous "lukewarmer" is Lucia Liljegren, a mechanical engineer (surprise!) whose blog, The Blackboard, can be found on the blogroll here. The Blackboard entertains many lukewarmers, along with a bunch of deniers and a smattering of pro-consensus folks, including myself.

Another self-described lukewarmer, Steven Fuller, has stepped into the giant floppy red shoes of Steven Goddard at WUWT, now that Steve has metastasized to his own blog. His self-description is the closest to providing a clear, testable proposition, as well as reflecting, by my reading, the central thrust of the comments by the "lukewarmers" on The Blackboard:

It’s because I am a ‘lukewarmer,’ one who believes that the physics of climate change are not by theselves controversial, but who believes that the sensitivity of the earth’s atmosphere to a doubling of concentrations of CO2 is not yet known, but is likely to be lower than activists have claimed.

Before I get into what the climate sensitivity might be, it's important to note who the lukewarmers are, which is slightly different from their self-definition. The lukewarmers to a person are critical of the IPCC, but when we take a look at the estimates of climate sensitivity cited by the IPCC, it's clear that thinking climate sensitivity is low is not enough to get on the outs with them:



Most estimates of climate sensitivity, regardless of how they are derived (and there are several lines of evidence including comparisons with paleoclimate, response to modern forcings like the Mount Pinatubo eruption, and climate modeling) include in their 95% confidence interval sensitivities between 1-2C. In some cases, the central estimate is between 1.2-1.5C for a doubling of CO2. So favoring a low number for climate sensitivity is not, by itself, enough to put you at odds with the "consensus." You need the other piece – the it's-not-a-big-deal piece. And that's where the trouble starts.

There is a half-full glass here, which is that a number of people who clearly identify emotionally and politically with the denialist movement have taken major steps towards the scientific consensus in order to maintain their credibility. While sharing the denialosphere's loathing of "activists" and its demonization of scientists like Hansen and Mann (whose unforgivable sin was to establish beyond a reasoned doubt that humans are causing a rapid and substantially unprecedented warming of the earth's climate) the lukewarmers avoid three major pitfalls of denialism:

1. They do not have to deny the basic physical laws which dictate that greenhouse gases cause warming.

2. They do not have to refute the massive physical evidence that the climate is warming.

3. They do not have to pretend that the vast majority of scientists who accept the theory of AGW are participating in a vast conspiracy to hide the truth about (1) and (2).

The lukewarmist position also allows one to position oneself as a moderate threading the needle between two extremes. Steven Fuller again:

The operation of CO2 as a greenhouse gas is one of the least controversial ideas in physics. The calculations that show a temperature rise of between 1 and 2 degrees Celsius if concentrations double is also widely accepted, including by all skeptic scientists without (AFAIK) exception.

We don’t know the sensitivity of the atmosphere to a doubling of CO2, so the effects of feedbacks are not know. Activists think it is 3 degrees or higher. Contrarians think it is very low–1, maybe 2, tops, some thinking it is even lower.
If activists are right we have a very big problem on our hands. If contrarians are right we don’t. If both are wrong, there is a lukewarmer’s way.

Note that the best science around puts climate sensitivity between 2.6-4.1C. It's not "activists" who put climate sensitivity at around 3C or higher – except as far as the activists are saying: Hey, those scientists that have spent their lives in this field probably are the best source of information regarding climate sensitivity.

The real contrast here is not between "activists" and "skeptics" but between deniers and everybody else – between the science and the right-wing lunacy. But lukewarmers are exploiting the shift in the Overton window brought about by voluble climate deniers to position their radical views as a sane middle ground.

Here's the problem. Lukewarmism doesn't get its adherents where they want to go – because even if we accept at face value their claims, the world would still require intense efforts to reduce the emissions of greenhouse gases in order to stave off disaster.

Scientists estimate a warming of 2C as the upper limit of what our civilization can adapt to, and not suffer disaster on a planetary scale. This is probably an optimistic number:

… even a “moderate” warming of 2°C stands a strong chance of provoking drought and storm responses that could challenge civilized society, leading potentially to the conflict and suffering that go with failed states and mass migrations. Global warming of 2°C would leave the Earth warmer than it has been in millions of years, a disruption of climate conditions that have been stable for longer than the history of human agriculture. Given the drought that already afflicts Australia, the crumbling of the sea ice in the Arctic, and the increasing storm damage after only 0.8°C of warming so far, a target of 2°C seems almost cavalier.

The hard lower limit of climate sensitivity -- the lowest it can possibly be and account for our direct observations – is about 1.1C (the real number is very likely to be in that range of 2.6C-4.1C – but we are following the "lukewarmist" argument to see where it leads). The change in forcings expected from a "business as usual" 21st century are +8.5W/m^2 – about 2 1/3 doublings of CO2.

Hence with the lowball number – the number Steven Fuller attributes not to lukewarmers but to out-and-out deniers – put us on course for 2.5C of warming this century. In other words, the lukewarmers' own numbers belie their causal attitude to reducing greenhouse emissions.

Now the deniers – sorry, excuse me, the "lukewarmers" – may say the projected emissions are much too high; that the IPCC is way off with those numbers as well. Or they could take the bull by the horns and claim, despite all the evidence to the contrary, that warm can tolerate warming of 3C or 4C without any major problems (the last time the world was that hot was several million years ago; there were no ice caps to speak of and the sea level was hundreds of feet higher). The trouble with that position is that it undermines the whole thrust of lukewarmism – which is to acquire credibility (or, to be fair, possibly to exercise intellectual honesty) via the advantages (1), (2), and (3).

Disputing one point with the scientific community – climate sensitivity – is compatible with a reasonable, pro-science argument. Hey, it happens -- an idea becomes the established consensus, and it turns out to be, not completely wrong maybe, but off (this has already happened several times in climate science -- unfortunately, every time, to date, the majority of the mistakes have been in the direction of under-estimating the speed and magnitude of the effects of global warming.)

However, when you begin to argue that not only does science have climate sensitivity wrong but also emissions and maybe impacts to boot – well, you're going to have a hard time explaining why thousands of scientists have made not one but a series of mistakes, all supposedly exaggerating the dangers of global warming. Go down that road, and pretty soon you're right back in the tinfoil-hat camp lukewarmist rhetoric was supposed to deliver you from. If you allege not one but a whole series of gigantic mistakes by huge numbers of investigators, all tending to undermine a scientific conclusion (only rapid reductions in emissions of greenhouse gases can prevent a substantial risk of planetary disaster) to which you are avowedly hostile, the simplest conclusion is not that you are a genius and the rest of the scientific community are fools; it is that you are a partisan and you are attacking science with implications contrary to your political goals.

In Part 2, I'm going to give the "lukewarmers" even more rope, and show how even widely unrealistic lowballing of climate change fails to make a rational case for business as usual.

Minor myth: If it's not unprecedented in the last 4 billion years, it's no big deal

Please don’t feed me some line of crap about how all the ice is going to melt. We both know the world has been warmer and the ice caps melted and sometimes they didn’t melt. In fact, the ice caps are actually a rare occurence in earth’s history so we should be surprised that they are even here.

-- Shooshmon, The Blackboard

This is a trope that recurs over and over in "skeptic" arguments: if a state of affairs has ever occurred before (even if we're talking about hundreds of thousands or even hundreds of millions of years ago) then it is not "unprecedented" and hence, no big deal.



I didn't find this myth at Skeptical Science (although #45, "Co2 was higher in the past," could be considered a specific instance) so it is officially in our purview as a minor myth.



Basically, the fallacy here relies on ignorance of just how long the earth has been around and how variable its climate has been over billions of years of geologic time. At times the earth has been covered in ice; at times the ice has melted, and sea levels have been hundreds of feet higher than today. The relevant question, however, is not whether a state of affairs has ever existed before, but what it means for us, people, and our seven (soon nine) billion-strong civilization.

The realistic way to relate these two ideas -- whether a condition has happened before, and what it's likely to be a problem for people -- is obviously not to look at the whole of geological time, but a much briefer span of time, human history, the time in which we have been living in settled communities and growing food to feed ourselves. Those are the conditions in which humans have prospered.

When we look at that period, approximately 13,000 years, we find something surprising. Let's take a look at Shooshmon's example (if that's not too strong a term), the ice caps, as reflected in sea level measurements:



Looks like quite a bit of variation. But look at the x-axis. It's marked in intervals of 50 million years. What does that have to do with anything human? Not much. Next, let's look at the recent past:



Over the last 8,000 years, sea levels have been rock-solid stable. That's the whole of recorded human history; China and Egypt, Judea and Babaylon, the Greeks and the Macedonian and the Roman Empires -- all of it. Prior, sea levels were lower (more ice). They have never been higher in all the time people have been growing their own food. So are higher sea levels safe, because the dinosaurs didn't mind them at all? Of course not. Among other differences, dinosaurs did not live by the hundreds of millions in costal cities and floodplains.

You can identify the same pattern in temperature records:



You can see semi-regular oscillations of several degrees. But always look at your axis. This is five million years of temperature records. The swings that seem to be coming one right after the other are actually occurring at a brisk rate of one every 40,000 to 100,000 years. Now look at it on a human timescale:



All of human civilization has lived in a band of +/- about 0.5C. Until the last decade, in which we've broken through that temperature ceiling headed for parts unknown -- headed, if things keep going on as they are, for conditions not seen on this earth for millions of years, things unknown not just to human civilizations but to the entire history of our species. Unprecedented? Maybe not in the strictest sense. Unsafe? You'd better believe it.

UPDATE: This exchange on The Blackboard captures the above in admirably terse style:

bugs (Comment#52733) September 24th, 2010 at 7:18 am

liza (Comment#52725) September 24th, 2010 at 5:50 am

Bugs, I know what the sea level height was 125,000 years ago because my husband is a geologist and I can google. That graph shows you that “today” isn’t such a big deal.

If you are a rock, or a planet, it’s not big deal.

WUWT lies like a rug -- where is Ben Lawson?

At the consistently fantastic "Wott's Up With That?" blog, Ben Lawson takes on the Herculean task of documenting and fact-checking the cornucopia of malicious nonsense that is "What's Up With That?" It's a mission I thought I'd be spending a lot more time on when I started this blog. One look at Ben's site convinced me that I could not do it more thoroughly, more tellingly, or with a lighter touch than him.

Lately, though, the effort seems to be taking its toll on Ben, who is often on hiatus, announced or unannounced.

My unsolicited advice; get some underbloggers. One man can shovel only so much treacle.

Ted talk on the oldest living things

H/t (not that they need it from me) to The Daily Dish:



One of these creatures has been alive for four hundred thousand years. It's incredible.

The most common measure of climate change is how the world is going to look in 2100. That's a useful signpost, but when you look at an 80,000-year-old tree, you can't help reflect on the narrowness of our horizons. The world's going to continue to turn, and the physics of greenhouse gases continue to operate, in 2101 and 2150 and 2200.

Should we think about how the world will look after we're gone? Should we worry about destroying unique patterns of life that have weathered nature's changes since before humanity came down from the trees?

We would be in a bad way if the Greeks and the Romans and the Caliphate hadn't had any concern for the next century or the next millennium. The cultural heritage, and the institutions of democracy and human liberty which grew out of them, would be gone. Billions of people around the globe build their lives around principles and precepts of Judaism, Christianity, Islam, Hinduism and Buddhism -- the youngest of which is more than a thousand years old.

Our modern world-spanning civilization is the richest, the most scientifically advanced society ever to emerge on this earth. Most of the people in past eras could not begin to conceive of it. It's richness is a result, in no small part, of the labors of philosophers, scientists, and artists, proselytizers and engineers of the last 5,000 years. They knew they were working for a future that stretched much further than a few decades, and we are all the beneficiaries of that legacy.

Have we now as a people embraced the role of the spoiled child, to be given everything and value nothing, work for nothing? Are we so rich and our lives so easy that the concept of building for the future has lost all meaning for us?

Another month, another humilation for "scientific forecaster" Scott Armstrong

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The original site Armstrong was using to track his bogus "bet," HubDub, has now vanished along with Armstrong's integrity and self-respect. The creators, who evidently have recognized in themselves a certain talent for make-believe, are now running a sports fantasy site. Fortunately Intrade is on the case; above you seeing Armstrong's chances of "winning" his own, self-designed, "Global Warming Challenge." It's now trading at 3.5%. No word from Armstrong, and still not updating the "bet." And while we're on the subject . . .

August UAH: 0.511C

. . . he's lost another month. That makes 7 out of 7 this year, meaning he loses 2010 as a whole (again, using his own nonsensical method of counting "winners" month by month of a ten-year prediction, and counting the winner of the most months as the winner of the year.) He's lost ten of the last eleven months. Here's a shocker -- he hasn't updated the status of the bet since March:



But here at the Idiot Tracker, we're happy to supply the assist to the eponymous Dr. Armstrong:

For April:

Armstrong: 0.263C
Gore (fictional): 0.348C
Actual (UAH): 0.50C

"Winner": GORE

For May:

Armstrong: 0.263C
Gore (fictional): 0.351C
Actual (UAH): 0.54C

"Winner": GORE


For June:

Armstrong: 0.263C
Gore (fictional): 0.354C
Actual (UAH): 0.44C

"Winner": GORE

For July:

Armstrong: 0.263C
Gore (fictional): 0.357C
Actual (UAH): 0.489C

"Winner": GORE

For August:

Armstrong: 0.263C
Gore (fictional): 0.36C
Actual (UAH): 0.511C

"Winner": GORE

You could set up this bet in a more honest, evenhanded way which might be semi-valid in terms of shedding light on what is happening with our climate. Needless to say, that's not the process Armstrong came up with, which makes it all the more amusing that he has managed to deal himself a losing hand from a stacked deck. The trouble with improving the process is that it make victory for Gore more or less assured. But let's look at what such a bet might be like.

For one thing, Armstrong has arbitrarily chosen the coolest of the four widely used global temperature data sets, Roy Spenser's UAH data:



NOAA NCDC: +0.163 C/decade

NASA GISS: +0.166 C/decade

UEA CRU: +0.158 C/decade

RSS LT: +0.164 C/decade


UAH LT: +0.140 C/decade

But even more basic, the notion that month-to-month temperature anomalies determine whether climate change is happening or not is silly. Obviously, if climate change is occurring, it's not going to change the fact that La Ninas lower temperatures, that solar activity goes up and down, or other random factors push the temperatures up or down. The sensible thing to do, and what scientists in fact do, is using moving averages. In other words, the last point in their graph is somewhere in the past, and they determine the average temperature using past and future readings. This smooths out the short-term fluctuations -- if each point on your graph represents a eleven-year average, chances are in that eleven years there have been a couple of La Ninas, and also a couple of El Ninos balancing them out. One really hot or really cold month no longer jerks the line up or down dramatically, which translates to the statistical equivalent of refuting global warming by pointing to snow on the ground (but what do you expect, really, when a guy with a degree in marketing proclaims himself a "scientific forecaster"?)

I mentioned eleven years; the sunspot cycle is eleven years*, so this is a commonly used period for averaging in climate studies. Why didn't Armstrong use an eleven-year moving average? Take a look at what such an average shows:



The herky-jerky of the annual anomalies is gone. In its place we see a smooth upward trend of rising temperature, with occasional brief pauses or accelerations. By the simple expedient of taking a moving average over time, the short-term fluctuations vanish, and the upward trend alone remains.

You can see how pointless a ten-year bet using this data would be. Temperatures have been going up steadily for 35 years; they aren't going to suddenly stop. It's hotter than it was ten years ago; ten years ago it was hotter than twenty years ago; twenty years ago it was hotter than ten years before that. Which is why, despite all the vocal deniers in the world, the ones proclaiming global warming is an obvious scam with no empirical evidence, mere "lying with graphs" as one denier put it, no one seems to be incline to put their money against a 0.15C rise in annual temperatures -- even at 30:1 odds.