Global Warming vs. Clojure

http://www.bestinclass.dk/index.php/2010/01/global-warming/

by abscondment • 16 years ago

69 28 16 years ago

bestinclass.dk

yannis• 16 years ago

Excellent read! Does anyone know of any study that extrapolates global temperatures from Landsat images?

tjic• 16 years ago

My first thought upon seeing the title to the post:

Q: What's the difference between Global Warming and Clojure?

A: Clojure is real.

jacquesm5• 16 years ago

By implication you're saying global warming is not real, and that's not true, global warming is real.

The questions center around how much of it is due to our influence and if we are capable of doing something about it.

jpwagner• 16 years ago

"global warming" is a phrase that has taken on a larger meaning than just increasing-average-temperature. his joke is obviously referring to the movement (he did capitalize.)

fleitz• 16 years ago

There is also the question of whether the net effect of the warming is a negative economic impact, and if so if "fixing" it is a greater cost to the economy than not fixing it.

alrex021• 16 years ago

I don't get this title. (In "1 line" of plain text) ;-)

[edit] jokes aside, its actually a good read.

mark_l_watson• 16 years ago

I just tagged this excellent article on delicio.us - description: "Awesome example of using Clojure for data manipulation!"

A good read, and I bet that a few of the code snippets in the article will save me coding time.

abscondment• 16 years ago

Totally.

The article is a good read regarding data crunching, but I take exception to some of his methodology.

Specifically, he's only using data from 1929 and on -- this is all part of the hockey stick's head. The 1920s are supposedly the start of the dramatic temperature increase. So of course the graphs don't show a dramatic slope change; there's no pre-1929, lesser-slope data included.

Edit: I'm not implying intentional omission on his part; 1929 is the earliest year available from NOAA (ftp://ftp.ncdc.noaa.gov/pub/data/gsod).

jacquesm5• 16 years ago

Exactly. That's about as selective as you can get.

No way of saying that hockey stick will appear if he includes all the data but the way he filtered out the end part and then stretched it is just being very selective with the data provided.

The reason why there is so much room for interpretation in all this data crunching in part is because of the troublesome normalization issues faced when consolidating data from so many different sources.

If there had been reliable weather stations in the last two millennia this would be completely different. But obviously that's not the case.

baguasquirrel• 16 years ago

So all we need to do in order to follow these stations, is filter out those in the northern hemisphere and re-run the job.

Isn't this the same sort of thing that the tree ring people did? There were some statistical points that looked like they were going to mess with the results so they threw them out? They only threw out a few outliers, which is standard practice, but here we're throwing out a whole class of data.

It's also interesting that the northern hemisphere is warming up faster (if the methodology chosen by the author is correct). Since most of the earth's landmass is on the northern hemisphere (as well as most of the developed countries), doesn't that mean we're in trouble?

By looking at each station indiviually instead of compressing them to an unevenly weighted average, we will be able to clearly deduce how the weather has changed through the years recorded.

This still doesn't take into account the density of stations. Also, trying to compare stations like that, with the curves obscuring each other, is a crime of presentation. If you took the time to do a regression on the datapoints with the other data, it surely would not have took much longer to code for regression on each of the individual weather stations (incorrect as that may be).

On a different note, the use of clojure was enjoyable, which deserves an upmod.

Zarkonnen• 16 years ago

As I understand it, the tree ring thing was that the more recent data is distorted by pollution. That is, the width of each year's ring should be dependent on how warm the year was, but the increase in pollution in recent times has caused a decrease in the width of the rings laid down.

dantheman• 16 years ago

There are a lot of problems with tree ring data, two of the most important are:

1. It no longer corresponds to the temperatures we measure (last 50 years or so)

2. It is based on very few trees,

motters2• 16 years ago

I have a project based on the Global Historical Climatology Network data, going back 300 years. This is based upon readings from actual thermometers on ground based weather stations, rather than tree rings or ice cores which are far more difficult to decypher.

http://code.google.com/p/tempgraph/

You can graph the data in various ways, all the way down to individual weather stations.

Kaizyn• 16 years ago

We (humanity) have reliable temperature data as measured by a thermometer and at fixed locations going back 300 years?

skorgu3• 16 years ago

We don't have temperature data measured by a thermometer at fixed locations for 50 years. There are many other sources of temperature data.

skorgu3• 16 years ago

I'm torn on this article. I'm very appreciative of a real-world example of using clojure to manipulate data but at the same time it treats a trivial and entirely unscientific analysis of one data set as a complete, concrete and comprehensive summary of an entire field of science.

mey• 16 years ago

I agree, I just choose to enjoy the presentation of clojure and ignore the conclusion. :)

holygoat• 16 years ago

That's not a very reasoned approach to contradictory conclusions.

brc• 16 years ago

Well, there's a few problems. Gore didn't actually use the Mann hockey stick that is presented, although the hockey stick in 'An Inconvenient Truth' is very simliar (in that it omits the Medieval Warming Period)

Those commenting on the start date fail to realise that the start date of the data set he uses is 1929. You can't blame the author for that.

The fact that it's part of the 'head' or 'blade' of the stick is irrelevant, all of the 'handle' is based on multi-proxy reconstruction, which has major data problems, as the endless to-and-fro on this issue says. One of the major problems highlighted has been the use of tree-rings as a proxy, and the tree rings do not agree with the instrumental record. This is the famous 'hide the decline', where the authors sought out statistical methods (the trick) in order to splice the tree ring proxies with the instrumental records, which they really shouldn't have done.

The field of coming up with global averages from temperature datasets is so complex I won't even try and make a comment on that. Plus I don't know any clojure.

Global Warming vs. Clojure

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