Does This Analysis Make My Tropics Look Big?

Guest Post by Willis Eschenbach

There is a new paper in Nature magazine that claims that the tropics are expanding. This would be worrisome because it could push the dry zones further north and south, moving the Saharan aridity into Southern Europe. The paper is called “Recent Northern Hemisphere tropical expansion primarily driven by black carbon and tropospheric ozone”, by Robert Allen et al. (paywalled here , supplementary information here  , hereinafter A2012). Their abstract says:

Observational analyses have shown the width of the tropical belt increasing in recent decades as the world has warmed. This expansion is important because it is associated with shifts in large-scale atmospheric circulation and major climate zones. Although recent studies have attributed tropical expansion in the Southern Hemisphere to ozone depletion the drivers of Northern Hemisphere expansion are not well known and the expansion has not so far been reproduced by climate models. Here we use a climate model with detailed aerosol physics to show that increases in heterogeneous warming agents—including black carbon aerosols and tropospheric ozone—are noticeably better than greenhouse gases at driving expansion, and can account for the observed summertime maximum in tropical expansion.

Setting aside the question of their use of a “climate model with detailed aerosol physics“, they use several metrics to measure the width of the tropics—the location of the jet stream (JET), the mean meridional circulation (MMC), the minimum precipitation (PMIN), the cloud cover minimum (CMIN), and the precipitation-evaporation (P-E) balance. Figure 1 shows their observations and model results for how much the tropics have expanded, in degrees of latitude per decade.

FIGURE 1. ORIGINAL CAPTION FROM A2012: Figure 2 | Observed and modelled 1979–1999 Northern Hemisphere tropical expansion based on five metrics. a, Annual mean poleward displacement of each metric, as well as the combined ALL metric. … CMIP3 models are grouped into nine that included time-varying black carbon and ozone (red); three that included time-varying ozone only (green); and six that included neither time-varying black carbon nor ozone (blue). Boxes show the mean response within each group (centre line) and its 2σ uncertainty. Observations are in black. In the case of one observational data set, trend uncertainty (whiskers) is estimated as the 95% confidence level according to a standard t-test.

I note in passing that the error bars of the observations are very wide. In fact, they barely establish the change as being different from zero, and in a couple cases are not statistically significant.

Now, several people have asked me recently how I can analyze a paper so quickly. There are some indications that set off alarms, or that tell me where to look. In this case, the wide error bars set off the alarms. I also didn’t like that instead of giving the claimed expansion per decade, they reported the total expansion over the 28 years of the study … that’s a second red flag, as it visually exaggerates their results. Finally, the following paragraph in A2012 told me where to look:

We quantify tropical width using a variety of metrics5,11: (1) the latitude of the tropospheric zonal wind maxima (JET); (2) the latitude where the Mean Meridional Circulation (MMC) at 500 hPa becomes zero on the poleward side of the subtropical maximum; (3) the latitude where precipitation minus evaporation (P-E) becomes zero on the poleward side of the subtropical minimum; (4) the latitude of the subtropical precipitation minimum (PMIN); and (5) the latitude of the subtropical cloud cover minimum over oceans (CMIN). To obtain an overall measure of tropical expansion, we also average the trends of all five metrics into a combined metric called ‘ALL’. Expansion figures quoted in the text will be based on ALL unless otherwise specified.

What told me where to look? Well, the sloppy citation. Note that they have not given citations for each of the 5 claims. Instead, they have put no less than seven citations at the head of the list of the five groups of observations and model results. That, to me, is a huge red flag. It means that there is no way to find out the source of each of the five individual observational results in A2012. So I went to look at the citations. They are as follows:

5. Zhou, Y. P., Xu, K.-M., Sud, Y. C. & Betts, A. K. Recent trends of the tropical hydrological cycle inferred from Global Precipitation Climatology Project and International Satellite Cloud Climatology Project data. J. Geophys. Res. 116, D09101 (2011).

6. Bender, F., Ramanathan, V. & Tselioudis, G. Changes in extratropical storm track cloudiness 1983–2008: observational support for a poleward shift. Clim. Dyn. http://dx.doi.org/10.1007/s00382-011-1065-6 (2011).

7. Son, S.-W., Tandon, L. M., Polvani, L. M. & Waugh, D. W. Ozone hole and Southern Hemisphere climate change. Geophys. Res. Lett. 36, L15705 (2009).

8. Polvani, L. M., Waugh, D. W., Correa, G. J. P. & Son, S.-W. Stratospheric ozone depletion: the main driver of twentieth-century atmospheric circulation changes in the Southern Hemisphere. J. Clim. 24, 795–812 (2011).

9. Son,S.-W. et al. Impact of stratospheric ozone on Southern Hemisphere circulation change: a multimodel assessment. J. Geophys. Res. 115, D00M07 (2010).

10. Kang, S. M., Polvani, L. M., Fyfe, J. C.& Sigmond, M. Impact of polar ozone depletion on subtropical precipitation. Science 332, 951–954 (2011).

11. Johanson, C. M. & Fu, Q. Hadley cell widening: model simulations versus observations. J. Clim. 22, 2713–2725 (2009).

For no particular reason other than that it was available and first in the list, I decided to look at the Zhou paper, “Recent trends of the tropical hydrological cycle inferred from Global Precipitation Climatology Project and International Satellite Cloud Climatology Project data”. Also, that was a citation that refers to the minimum precipitation (PMIN) for both hemispheres, as used in A2012. Figure 2 shows results from the Zhou paper:

Figure 2. ORIGINAL CAPTION FROM ZHOU: Figure 4. Time‐latitude cross sections of zonal mean seasonal precipitation and the corresponding linear trend with latitude. Solid orange lines mark the 2.4 mm d−1 precipitation threshold which is used as the boundaries of subtropical dry band. The boundary at the high and low latitude of the dry band is used as a proxy of the boundary of Hadley cell and ITCZ, respectively. Solid black lines indicate latitude with minimum precipitation. Dashed red lines mark the Hadley cell boundary determined by the 250 Wm−2 threshold using HIRS OLR data.

Now, the black line in these four frames show the minimum precipitation, so that must be where they got the PMIN data. So I went to look at what the Zhou paper says about the trend in the minimum precipitation PMIN. That’s shown in their Figure 5:

Figure 3. ORIGINAL CAPTION FROM ZHOU: Figure 5. Linear trends of the latitude of minimum precipitation, ITCZ, and Hadley cell boundaries inferred from GPCP for each season and the year marked on the horizontal axis for (a) the Northern Hemisphere and (b) the Southern Hemisphere. … Leftmost, middle, and rightmost bars in each group are for minimum precipitation, Hadley cell, and ITCZ boundary, respectively. For quantities significant at the 90% level, bars are shaded green, blue, and orange, respectively.

Now, let me stop here and discuss these results. I’m interested in the “Year” category for minimum precipitation (green), since that’s what they used in the A2012 paper. Note first that the minimum precipitation results that they are using are not even significant at the 90% level, which is very weak. But it’s worse than that. This paper shows one and only one result that is significant at the 90% level out of a total of six “YEAR” results.

This brings up a very important and routinely overlooked problem with this kind of analysis. While we know that one of these six “YEAR” results appears to be (weakly) significant at the 90% level, they’ve looked at six different categories to find this one result. What is often ignored is that the real question is not whether that one result is significant at the 90% level. The real question is, what are the odds of finding one 90% significant result purely by chance when you are looking at six different datasets?

The answer to this is calculated by taking the significance level to the sixth power, namely 0.96, which is 0.53 … and that means that the odds of finding a single result significant at the 90% level in six datasets are about fifty/fifty.

And that, in turn, means that their results are as meaningless as flipping a coin to determine whether the tropics are expanding on an annual basis. None of their results are significant.

It also means that the data from the Zhou paper which are being used in the A2012 paper are useless.

Finally, I couldn’t reproduce either the average value, or the error bars on that average, in the A2012 “ALL” data. Here are the “ALL” values from my Figure 1 (the A2012 Figure 2):

Item, Value, Error

JET, 0.45, 1.09

P-E, 0.75, 0.29

MMC, 0.24, 0.08

PMIN, 0.17, 0.51

CMIN, 0.33, 0.06

ALL, 0.33, 0.12

When I average the five values, I get 0.39, compared to their 0.33 … and the problem is even greater with the error bars. The error of an average is the square root of the sum of the squares of the errors, divided by the number of data points N. This calculates out to an error of 0.25 … but they get 0.12.

Does this mean that the tropics are not expanding? Well, no. It tells us nothing at all about whether the tropics are expanding. But what it does mean is that their results are not at all solid. They are based at least in part on meaningless data, and they haven’t even done the arithmetic correctly. And for me, that’s enough to discard the paper entirely.

w.

PS: I suppose it is possible that they simply ignored the results from the Zhou paper and used the results from another of their citations for the minimum precipitation PMIN … but that just exemplifies the problems with their sloppy citations. In addition, it brings up the specter of data shopping, where you look at several papers and just use the one that finds significant results. And that in turn brings up the problem I discussed above, where you find one significant result in looking at several datasets.

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ImranCan

Superb ….. just shows how little one has to dig to expose the smell of bullshit. Honestly – what has science come to ?

Why would Southern Europe have to become more arid? Isn’t there quite a sizable sea in there somewhere, quite capable of dampening the impact of shifting climate zones?
Or are we supposed to believe the Mediterranean would move away, dry up or simply go to sleep and react not a peep to the new climatic conditions?

Paul Carter

Excellent work Willis – clear and to the point. This review is exactly what the peer reviewers should have done and had this paper terminated before publication.
I wonder if the peer reviewers understand that their job isn’t simply to peer at the paper – they’ve actually got to do some review.

Robert

very well done Willis……excellent analysis

Willis, you say: “This would be worrisome because it could push the dry zones further north and south, moving the Saharan aridity into Southern Europe.”
Even if this is true, that would also imply that tropical rains would come to an expanded region of Africa. It seems to me that the total arid land area would decrease, at least with respect to Europe and Africa as a combined region.
So one could argue that on balance, it would a net plus for both Europe and Africa as far as food production is concerned. Unless of course the hope is for Europe to have a better climate and more food security than Africa.
I’m just saying that the premise for alarm here with this prospect of expanding tropics is based on what seems to me to be an unfortunate bias. Wouldn’t the objective view be that it doesn’t matter what minor countertrend happens to a given region or group of people, only what happens to the world overall?
That said, I don’t want to see Europe have to go through any difficulty either, but surely they are better equipped than most to adjust to new problems? (Importing food, adopting new agricultural practices, desal including the cost of power to run the desal plants …. ) So if the overall global impact is more precipitation, more arable land, more food production, and more and cleaner water for the people, and a reduction in the cost of all these things (again, looking globally and factoring in any increased difficulty in a certain region), can that really be seen as anything but positive?
RTF

I question the black carbon aerosols heating the planet. They cannot create heat only adsorb solar heat and get warm themselves, which costs energy, and radiate heat at a lower level due to the energy lost warming them, to the surroundings. This will lower heating at the surface not increase it. These warming effects seem to violate both 1st and 2nd laws. Also the vegetation response to warming lags that heating by several years it will still be evident when temperatures fall then start to die off. 8000 years ago there was no Amazon rain forest, it was grassland, and the Sahara was forested. The planet was cooler then due the last major ice age finishing 2-3000 years previously. It has also been warmer than today during the MWP, RWP and Holocene Climate Optimum but as far as I can tell from research of those times the tropics remained roughly where they are now.
There seems to be no recognition that climates change with corresponding environmental changes and this due to the changing natural climate drivers.

Warm times are wetter. Cool times are drier. (i forgot to add that)

bsk

Nice job on one cite, but the analysis really requires an understanding of them all. Kinda sloppy review…

ChrisH

The poor statistical review of papers which rely heavily on convoluted statistics seems to be a major issue with “climate science” papers. In my own, medical, field papers with this level of statistical content would be rejected unless we had a recognised statistician as a co-author. Even then, a specialist statistical review would be required.

Alastair

The geometric mean of those data, rather than the arithmetic mean (average) is perhaps what they calculated? (=GEOMEAN(x1,x2,x3,x4,x5))

R Barker

Some of us like “big tropics”.
Your analysis brought to mind an editorial in the 10 May 2012 Nature by Daniel Sarewitz about the bias making its way into scientific research if for no other reason than expecting to get the desired result. http://www.nature.com/news/beware-the-creeping-cracks-of-bias-1.10600

Peter Miller

This brings up the obvious differences between peer and pal reviews. With relative ease, as he he has done so often before, Willis does an excellent hatchet job on the data analysis and ‘models’ in this paper.
So does pal review in ‘climate science’ mean: i) nobody reads anyone else’s paper for fear of finding something wrong in it, ii) nobody reads anyone else’s papers because they are too lazy, or iii) the pal, or peer, has insufficient knowledge and/or mental ability to understand the contents of. the paper?
The bottom line: It’s ‘climate science’, where the rules are different from all other fields of science. Anything goes, as long as it supports ‘The Cause’.

DocMartyn

The data in the Zhou paper is obviously not normally distributed, and yet is treated as if it is. It is then combined with other data-sets and again treated as Gaussian..

richardscourtney

bsk:
At May 22, 2012 at 4:41 am you write;

Nice job on one cite, but the analysis really requires an understanding of them all. Kinda sloppy review…

No!
When you are considering buying a car and the first wheel you examine is damaged, then you do not need to see the other three wheels to know the car needs repair before you buy it. You do not require an examination of the other wheels to know that.
Similarly, only a fool would ‘buy’ the message of this paper because – as Willis has shown – the first piece of evidence used to form that message is ‘not fit for purpose’. You do not require an examination of the other pieces of evidence to know that.
You comment is a kinda sloppy review of Willis’ work. Nice try, though.
Richard

Shevva

I’m sure Mr. Allen doesn’t really care, someone gave him a grant.

cui bono

Thanks Willis! So everything moves N’ward, and the green pastures of Britain become the parched scrub of Spain?
In 2010 the UK National Trust suggested that gardeners replace traditional British lawns with cacti, and orange and lemon trees, in order to prepare for global warming.
Due to freezing, snowy winters, anyone taking this horticultural advice would now have a very low-maintenance garden! 🙂

Shevva

PS. It’s what I term beer review ie. if you let my paper through without actually reading it I’ll buy you a crate of beer.

Pamela Gray

What is the difference between GSA fubar party expenditures in Vegas and climate science research like this one?
None. Note to the current President (no disrespect intended). I want my money back.

Rob Potter

Nice work Willis.
The bit that I liked was where you deconstruct the “significant” result to show that it is actually an expected outlier, given the number of observations. Matthew Briggs has done a good job of explaining the ways in which you can “generate” statistically significant results (based on arbitrary 0.1 or 0.05 levels of probability), but it does not often get brought into other critiques.
If I could make one plea to reviewers of papers where such stats are (ab)used, I would ask them to require authors to state how many parameters were evaluated before picking a particular one as significant. The ‘gold standard’ of 0.05 really just means one in 20 and if you are looking at 20 variables, it is completely unremarkable if you find a 0.05 level in one of them. This level of mis-use of statistics is rife in all branches of science.

Jer0me

Sorry if this has been said before, but surely ‘the tropics’ are a well-defined astronomical feature: They are the latitudes at which the sun is directly overhead at the solstice.
Am I missing something here?

Jer0me

… oh, and “Saharan aridity” has nothing to do with the ‘tropics’. Such aridity occurs well outside the tropics too. It is a product of the ‘weather’ in certain geographical regions. Otherwise you would not get the lush verdant flora that is typical of the tropics.

HaroldW

[typo, should be “precipitation-evaporation balance”]
Willis, I’m not sure why you’re objecting to using the Zhou et al. Pmin figure. In the table, it is given as 0.17 +/- 0.51. While not significant in and of itself, there’s nothing statistically invalid about combining measurements which individually are not significant.
.
Also, for the “All” figure — if one has metrics with different errors, a simple average isn’t the best approach. A weighted average, weight being inversely proportional to the square of the error, would seem appropriate. [Although only two metrics dominate the calculation; the others become essentially irrelevant.] But that method doesn’t produce the paper’s 0.33 +/- 0.12 result either.

ferdberple

One of the previous articles (see below) showed a 200 year natural pattern driving the winds north and south, which would explain any small observed change in the tropics. No carbon black required.
As I gather the gist of this article is that climate models are more sensitive to carbon black than they are to GHG in predicting a change in the tropics. Since climate models don’t account for observed natural cycles and climate science has no explanation for why they occur, this paper really is talking about the limitations and sensitivities in climate models, while conveniently missing the point that models are not climate.
Premonitions of the Fall (in temperature)
Posted on May 20, 2012 by Anthony Watts
Guest post by David Archibald

Stephen Richards

ImranCan says:
May 22, 2012 at 4:10 am
Superb ….. just shows how little one has to dig to expose the smell of bullshit. Honestly – what has science come to ?
OR
Superb ….. just shows how little one has to dig to expose the bullshit below the smell. Honestly – what has science come to ?

ursus augustus

I think Shevva nails it – its about the grants and getting the next one – think of a paper you can concoct and apply for a grant. Some time back now I was lecturing at a local university on a part time basis and my department head ( a professor and still a good pal) eventually approached me about publishing a paper. I baulked at first because I am not an academic but a working engineer. As it happened I was the first one to start using the university’s recently acquired CFD code, had built up some basic expertise, had used it under a commercial licence and was including its practical use in my engineering design project class. So we decided I would do a paper in that area. When I said I could do something on using CFD in design and elaborated he said “great, there are at least two LPU’s in that”. LPU I asked? What is an LPU. Least Publishable Unit was the reply. It was an epiphany as to how academic funding is influenced and explains an awful lot about the practice of climate science. I eventually wrote the paper, got sent to a conference on the other side of the country, a good time was had by all and the department notched up a few grand in additional funding brownie points plus expenses.

Don Keiller

But it was in “Nature” it must be true!!!

AJ

Was “the minimum pressure (PMIN)” meant to say minimum precipitation?
Wouldn’t a reanalysis product be useful in diagnosing tropical expansion? Then again, interpolated datasets have their own limitations.
[Thanks, fixed. -w.]

When you have no understanding, all you have is statistics.

DD More

Although recent studies have attributed tropical expansion in the Southern Hemisphere to ozone depletion the drivers of Northern Hemisphere expansion are not well known and the expansion has not so far been reproduced by climate models.
If other cases are to be followed, since the models do not show expansion, it must not be happening.
Here we use a climate model with detailed aerosol physics to show that increases in heterogeneous warming agents—including black carbon aerosols and tropospheric ozone—are noticeably better than greenhouse gases at driving expansion, and can account for the observed summertime maximum in tropical expansion.
From the looks of their Fig 1, the model results miss the observation by both model & observed error margins? How is this model better?

ferdberple

DocMartyn says:
May 22, 2012 at 5:06 am
The data in the Zhou paper is obviously not normally distributed, and yet is treated as if it is. It is then combined with other data-sets and again treated as Gaussian..
========
This is a very good point. Time and time again we see climate science performing statistical analysis under the assumption the data is normally distributed, without any evidence this is a correct assumption.
Time series data is rarely normally distributed. Yet climate science proceeds under the assumption that it is – without having shown this to be true.
There is a simple eyeball test to check if climate data has a “normal” distribution. When data has a normal distribution, as you expand the scale the data will “smooth”. So, for example, while daily temperatures might fluctuate quite a bit, as you expand out to decades and centuries, this fluctuation should “average out”.
And, when we look at the famous “hockey stick” that is what we see. Centuries of past history where the temperature doesn’t fluctuate much at all. This is modern climate science.
However, when we look at other measures of climate before “the Team” and the IPCC controlled what was published, we see quite a different picture. When we expand the scale beyond 10 thousand years we see huge NATURAL variations in temperature. Even Gore showed this in his movie.
This increasing natural variation that appears as we increase the scale tells us the climate is not normally distributed. Climate is not a coin toss. The odds of temperature going up and down do not remain constant year to year, century to century. You cannot use mathematical techniques that assume the odds remain constant.
Thus, statistical analysis that relies on the assumption of normal distribution is bogus. The conclusions in much of modern climate science are a result of the faulty application of mathematics to “prove” a foregone conclusion. That foregone “conclusion” is that climate remain constant, except for human activity. Using mathematical methods that assumes this to be true is what makes it appear true.

Willis
Your trenchant, witty, searching analyses of made-up-science do a service to all sceptics and dissenters and show everyone what proper science should look like.
I particularly like your ‘smelly’ categories. Things that set your BS detector nose twitching! Journal editors and peer reviewers should draw up an audit list based on your work. It would filter out the most egregious rubbish. Thanks again – bloody brilliant!

johanna

Have to agree with Jerome here – Willis, as a former resident of the tropics, how did you let them get away with that? Are they saying that monsoons become prevalent in southern Europe?

Stephen Wilde

The paper is clearly rubbish, as Willis says, but at least the focus is shifting towards the very phenomena that I have been banging on about for over 4 years now.
I don’t think there is any serious disagreement with the observation that in the late 20th century warming period the jets became more zonal and the equatorial air masses did expand poleward a little and that the scenario now with the less active sun is very different.
Similarly there is lots of evidence that the MWP had zonal jets and expanded tropics whereas the LIA had meridional jets and contracted tropics.
To whom should I apply for grant monies ?

Willis Eschenbach

HaroldW says:
May 22, 2012 at 6:31 am

Willis, I’m not sure why you’re objecting to using the Zhou et al. Pmin figure. In the table, it is given as 0.17 +/- 0.51. While not significant in and of itself, there’s nothing statistically invalid about combining measurements which individually are not significant.

Thanks, Harold. I object because the error is not correctly represented. As I showed above, even a result that appears to be significant is not significant if you have searched through six datasets to find it. Similarly, the results which are not significant are even less significant if you search through six datasets to find them.
If you are doing that kind of selective picking of individual results gleaned from casting a wide net over a large number of datasets, you can find any kind of result that you wish and use it … but that doesn’t magically make it significant.
w.

mojo

Himalayas on the move, are they?

From their caption:
“…(Observed and modelled 1979–1999)…In the case of one observational data set, trend uncertainty (whiskers) is estimated as the 95% confidence level according to a standard t-test…”
And you’re telling us they never, ever mentioned which one it was?
Also, is a period of 20 years sufficient to make these claims?
Especially since wiki states “…The region (Sahara desert) has been this way since about 1600 BCE, after shifts in the Earth’s axis increased temperatures and decreased precipitation. Then, due to a climate change, the savannah changed into the sandy desert as we know it now…” – if those natural events were that strong, then the tropics would have gone through a large transformation too.
This means that natural events centuries ago had a greater effect than the current CO2 levels.

Joe Zarg

“Wouldn’t the objective view be that it doesn’t matter what minor countertrend happens to a given region or group of people, only what happens to the world overall?”
Why should anyone try to be objective? Each of us, if he is normal, puts his own people first, and mine are Europeans and those who are derived from Europeans.
So I want Europeans, in that wider sense, to come out ahead of anyone else, including Africans (though I wish the Africans well).

Curt

Jer0me, johanna,
What is being discussed here is possible movement of the tropical Hadley cell circulation. Roughly speaking, the intense sunshine at the equator causes a massive uplift of air there. At high altitudes, this air moves away from the equator, both to the north and south. At about 25-30 degrees of latitude, this air falls. Over land at least, there is virtually no moisture in this air, and the result is deserts, such as the Sahara.
There are at least potential reasons to believe that in a warmer climate, this region of dry falling air would move farther away from the equator. For example, in the cool 1970s, the Sahel, the boundary region between the Sahara and the lush tropics in Africa, was drought stricken, causing much misery. In the warmer decades since, it has been much wetter. Anyway, this is the possible effect that is in play here.

Willis Eschenbach

curryja says:
May 22, 2012 at 7:39 am

Willis, check out this paper
http://webster.eas.gatech.edu/Papers/Hoyos_Webster2011.pdf

Thanks as always, Judith. I got very nervous when I looked at their Figure 1 (a).

The problem is, where are the error bars? So I looked at the dataset description, where they say that the 95% confidence interval for their data is about 1.6°C … and the total warming shown over the period is only about 0.8°C … not a healthy combination.
I’ll take a more detailed look at it later today, but that’s not a good start.
The second problem is that the analysis revolves around the area of the Pacific Warm Pool, which is an area little traversed by ships. As a result, the errors in that calculation are going to be even larger … and are also not mentioned.
All the best,
w.

Gail Combs

Richard T. Fowler says:
May 22, 2012 at 4:20 am
Willis, you say: “This would be worrisome because it could push the dry zones further north and south, moving the Saharan aridity into Southern Europe.”
Even if this is true, that would also imply that tropical rains would come to an expanded region of Africa. It seems to me that the total arid land area would decrease, at least with respect to Europe and Africa as a combined region.
So one could argue that on balance, it would a net plus for both Europe and Africa as far as food production is concerned…
___________________________________
You beat me too it. It would also might increase the growing seasons in Canada, Russia and China, a very big plus.
Paul Vaughan presented this graph yesterday in another thread. It shows the hot temperatures are not linked to the equator but to dry land between 15 and 30 degrees latitude: http://i55.tinypic.com/dr75s7.png

Gail Combs

Rob Potter says:
May 22, 2012 at 5:57 am
…..If I could make one plea to reviewers of papers where such stats are (ab)used, I would ask them to require authors to state how many parameters were evaluated before picking a particular one as significant. The ‘gold standard’ of 0.05 really just means one in 20 and if you are looking at 20 variables, it is completely unremarkable if you find a 0.05 level in one of them. This level of mis-use of statistics is rife in all branches of science
_________________________________
I am not sure if it is true now, but statistics was not even a required course when I got my BS in Chemistry. Some of the industry courses I took were only a “How to” course on what buttons to push to get “statistics” out of the “Statisitical Package” being sold to the company. Only by taking college level stat courses as part of my continuing Ed did I actually get any of the math and a few courses just barely scraps the surface.
Given Phil Jones, remark about Excel, I am afraid this is typical of science where “the one (statistical) course man is king”

johanna

ferd berple says:
May 22, 2012 at 7:18 am
DocMartyn says:
May 22, 2012 at 5:06 am
The data in the Zhou paper is obviously not normally distributed, and yet is treated as if it is. It is then combined with other data-sets and again treated as Gaussian..
========
This is a very good point. Time and time again we see climate science performing statistical analysis under the assumption the data is normally distributed, without any evidence this is a correct assumption.
Time series data is rarely normally distributed. Yet climate science proceeds under the assumption that it is – without having shown this to be true.
————————————————————————————-
I have just done 15 rounds with someone in another forum about so-called ‘cancer clusters’ about exactly the same issue. Unsurprisingly, a combination of electromagnetic radiation and ‘chemicals’ were being blamed in that case. It is hard enough to be arguing with members of the general public about this; it must be infuriating to have to do it with people who claim to have scientific training.

John F. Hultquist

Stephen Richards says:
May 22, 2012 at 6:46 am
ImranCan says:
May 22, 2012 at 4:10 am
Superb ….. just shows how little one has to dig to expose the smell of bullshit. Honestly – what has science come to ?
OR
Superb ….. just shows how little one has to dig to expose the bullshit below the smell. Honestly – what has science come to ?

OR . . .
Superb … just shows how perceptive, persistent, and capable one has to be to expose climate science chicken dung.
There—fixed it for y’all.

Gail Combs

Stephen Wilde says: @ May 22, 2012 at 7:34 am
…To whom should I apply for grant monies ?
___________________________
To the US government of course. I am sure there is lots of Obama Money left since Bernanke is printing more money.
Just do not forget the get out of peer-review free card “This study shows that increases in heterogeneous warming agents such as carbon dioxide drive….”

SteveSadlov

It’s easy to confuse the expansion of equatorial humid zones (and subsequent greening of the “Horse Latitudes” deserts) with overall tropical expansion. Of course, the most recent such “greening” humid zone expansion was during the late 20th Century. It was good while it lasted, but with every day becomes a fading memory. Now onward into a cold and dry age. An age of death.

oMan

Willis: another awesome entry at WUWT. Thanks very much. I appreciate not only the pithiness of your analysis (and the unique flavor of it) but the very useful description of “red flags.” The disconnect between their citations and the underlying scholarship (Zhou) is really disconcerting. Do they not realize how sloppy they are? Or are they just assuming that most of us won’t dig below the first belt of citations?
More generally it seems to me that scholarship is based on trust; that the coin of trust is debased by inept, or careless, or fraudulent citation; that citations “stack” on each other; that we are now so caught up in a network of stacked citations that, once we cease to trust the network, we will find ourselves not just one or two steps back, but way back. Is there not room for an independent checker-of-trustworthiness? Clearly the old (peer-reviewed publication) system is not working very well. The market for trustworthiness would, or should, pay handsomely for a better system. Look at the sums we are prepared to gamble on the putative findings of these papers…

Tony Mach

“There is a new paper in Nature magazine that claims that the tropics are expanding. This would be worrisome because it could push the dry zones further north and south.”
As far as I understand, the dry zones are dry, because there is little rain that falls – not because of the temperatures. So it doesn’t automatically follow that if the tropics expand, that the the dry zones will be pushed away. The precipitation pattern is the one to watch – if you can formulate such a model that is both simple as well as close to real world for precipitation, you could earn several prizes.

Look at the years … 1979 through 1999, basically a warm-phase PDO oscillation as Dr. Easterbrook has established.

Kelvin Vaughan

Does This Analysis Make My Tropics Look Big?
No Darling!