Does anyone honestly think the 1200 km smoothing accurately reflects real Arctic temperatures?

To paraphrase Galileo ‘But still it melts!’

However the HadCRU data excludes a great deal more than just the arctic. As far as I can see they only use data from 5 x 5 degree grids in which there are reliable instruments. This figure has changed a lot over the years. Back in 1850 they covered just 22%, in 1989 the figure reached 89% – but this figure has now dropped back to 81%.

Since – as I understand it – GISS and HadCRU use exactly the same temperature data, the only difference being the way it is dealt with, then one has to make a choice over which one prefers. Is it better to give each station equal treatment in the way that HadCRU does, or should one extrapolate the data from some stations over areas where there are no reliable thermometers? Does the GISS extrapolation risk increasing errors from marginal stations, or does ignoring 19% of the globe mean that HadCRU is not really a global average at all?

Bear in mind that many of the more remote 250 km blocks have data from only one station in the grid cell, which is really just a miniscule dot in the image.

As you can see, the 250 km image reveals just how little Arctic data there really is!

Does anyone honestly think the 1200 km smoothing accurately reflects real Arctic temperatures?

Of course, keeping the instrument noise by ignoring additional data keeps the error bars wide. That’s one of the reasons Tamino’s error bars are wider than mine. Wide error bars makes it difficult to falsify anything– what with the high β error, which is the error driven down by loads of data.

So, if you don’t want to find any problems with the IPCC projections it’s easy enough to do so. Just ignore most of the data.

But, yes. If I ignored 80% of the existing data, and picked the outlier, I too, would make the same conclusion as Tamino.

Isn’t it amazing how I guessed precisely how he would come to his conclusions?

when Tamino was proposing a bet on climate trends, here is what he said about choosing a temp series

[Response: None of the metrics — popular or not — is 100% correct. And correcting the GISS Y2K error led to a net change in global average temperature anomaly of 0.003 deg.C.

As I said, I’m not betting money I’m trying to establish conditions under which we can confirm or deny various hypotheses. It was framed as a bet because that seems to be popular for discussion, and it does force one to be explicit about exactly what conditions will lead to a declaration for one or another hypothesis. For a bet, I think it’s better to keep it simple and agree on a single source of data for decision.

But for determining the outcome with highest reliability it’s better to use multiple data sets. I intend to keep track of GISS, HadCRU, and NCDC, and I’ll probably keep my eye on satellite data from RSS, UAH, UMd, and UW as well. I’ll report any significant results, regardless of the nature of the result or the source of the data. I expect they’ll end up telling the same story.]

So BORIS, Didnt Lucia do what Tamino suggested on jan 31 2008? use all the indexes? and isnt this the proceedure he claimed would have the HIGHEST reliability? And then, in march when lucia uses all the indices to challenge the IPCC, did tamino resort to picking the SINGLE index that best made his case?

LOOKS LIKE you just pwned yourself.

http://tamino.wordpress.com/2008/01/31/you-bet/

Well?

GISS estimate the polar regions from stations 1200km away and they employ a GCM to aid in this process. HADCRU
live with the added uncertainity in their estimate.

But, as I said, in a reply to me tamino has said that he PREFERS the hadcru approach. be that as it may. Lucia
uses them all, so she wins and has picked no cherries.

(Graphs work great. I do take the liberty of editing to make them show.)

What we see is this has persisted over several cycles. The peaks are systematically dropping and the troughs are too.

Who is to say this isn’t the trend for that region? Due to some other cycle?

The idea of the perfect ENSO is that we haven’t sampled many. But look at that graph– we’ve sampled several. And the graph is strongly suggestive of a downtrend that is entirely separate from ENSO!

Is there something else? I don’t know. But this graph does not look like we just happened to catch ENSO at a high and leave it at a low.

If, on the other hand, this is due to ENSO, we should see the apparent trend reverse when we hit the top of the next ENSO. That is simply a matter of time.

The timeseries below shows SST anomaly in the region 180w-80w/5s-5n, data source is ERSSTv2(not the latest version used by NOAA merged land/ocean index),i’ve computed anomaly with respect to a 1971-2007 climatology:

Slope is -1.03°C/decade.
This can be verified looking at the graph, it shows a decrease of red line from +0.56°C in february 2001 to -0.16°C in february 2008, a 0.72°C drop in seven years , which equals 1.03°C/decade.

I’ve said that tamino has good reason to select GISS. You may disagree with the reason; however, accusations of cherrypicking–especially when one has not even investigated the reason for the choice–are mere rhetorical ploys to advance one’s own arguments. Can we dispense with the sophiostry, please?

What’s the difference between CRU/GISS and RSS/UAH?

As far as I can tell, that image shows us that a small region of water is 0.5C cooler now than in 2001. As anomalies go, that is small. (Note, the overall range is 8C during that period.

Equally importantly, that is a simple difference. (This is what I suspected, and why I wanted you to use words.) Simply taking the difference in means is not the effect that would have on a linear regression in the trend.

hat are the units on your chart? Degrees C? Degrees C/month? Was what you call a trend computed using OLS? Or is it just an anomaly?

My difficulty isn’t one with your choice of data. NOAA data are fine. But you need to describe what you did.

http://data.giss.nasa.gov/gistemp/maps/

However, with regard to testing theories against observations, the fact that data rely on filling in regions using a theory rather than measurements is a short coming.
I don’t need to rebut anyone’s article to point out this difficulty.

Obviously, Hansen’s use of theory to fill in for lack of measurements is not the only possible shortcoming in data. We could argue which system is best until the cows come home. Recognizing that all measurement systems include ‘instrument’ noise, I use all sets that are considered sound.

Assuming that each of the four ( and soon five) measurement sets I use is one “realization” of a different set of climatologists judgement for the “real” data, I am ensemble averaging over all these realizations. This should minimize the “instrument noise” in the same way that modelers using GCM’s try to average out errors due to modeling uncertainties using their differnt “GCM-Model-planet-Earths”.

Of course, if the entire universe of climatologists agreed wholeheartedly with Hansen, they would all use his method. In that case, their judgement would be reflected in the average data. Right?

And here is again NCDC trend with more information,first term is excluded so trend are computed between february 2001(not january) and february 2008 (I changed levels so colors are not the same):
http://img397.imageshack.us/im.....endoc9.png

seond graph is simply a zonal mean of trend as explained above.

Henry, NASA GISS has greater trend due both to arctic interpolation and interpolation over land (particularly eurasia), while Hadley dataset has lot of missing pixel there, since both arctic and eurasia warmed very fast in recent year(look at trend above), nasa giss vs hadley temperature difference became larger over time and reached a max in 2007 when both arctic and eurasia has been very warm…you couldn’t expect a costant difference.
bye,bye.

We are discussing Lucia’s post and Tamino’s rebuttle. Lucia used all available data. Tamino only used GISS and censors posts that try to point out that any dataset other than GISS would fail his C-O test. Any rational observer can see that Tamino is the cherry picker in this case. Your ’skeptics do it too’ defence is rediculous.