Posts by PeteB

Painting by numbers: NASA's peculiar thermometer

1% of the globle

In fact, the HadCRUT3gl.txt file (HadCRUT3 for the globe) lists the fraction of the earth's surface which is covered by their analysis, and for 2007 it was 82%, so that fully 18% of the globe isn't estimated by HadCRU.

Reasonable question

Hi Evan - comparing the longer term trend for surface temperature with other temperature reconstructions (adjusted to a common reference period) :

http://tamino.files.wordpress.com/2008/01/big3z.jpg

can't really see much difference

"In fact, since 1998 (or 2002), RSS and UAH show a bit of a cooling trend while GISS definitely trends warmer. Again, there differences aren't big, but the changes they are being compared with aren't big, either. Steve Goddard points this out a couple posts prior"

- isn't that just because the satellite measures show a much bigger peak in 1998 ? (which you would expect because El Nino has more tropical warming which affects the lower troposphere more than the surface temperature)

http://tamino.files.wordpress.com/2007/08/global2.jpg

"So if surface and troposphere do match it implies that either the tropospheric has too low a trend or the surface has too high a trend"

agreed - although there is obviously error bars associated with each. The graph above shows a higher satellite trend than surface trend (although not by 20%)

The only other point is when you compare recent GISS to HADCru you can see some slight differences - but I think this i nearly entirely due to the different ways they treat polar regions - HADCru (and the satellite reconstructions) effectivelty ignore some of the polar regions whereas GISS extends the temperature gradient from the equator towards the poles and extrapolates it over the poles.

RE NOAA's arc

Evan,

I have read the various CA posts and the thing I still don't understand is, if any of these objections are significant, why wouldn't there we see some divergence of GISS from the other temperature measurements over time - I can see different size peaks and troughs between the temperature series but overall they seems to follow the same track - if what you say is happening was true I would expect GISS to be start off significantly cooler and end up significantly warmer

see http://tamino.files.wordpress.com/2008/03/4way.jpg

Try again

My last comment seemed to fail moderation :-)

There is very good agreement between all the data sets sets

http://tamino.files.wordpress.com/2008/03/4way.jpg

Also El Nino years (1998) will produce higher lower troposphere (ie satellite) temperature rises because more warming is near the equator.

Is the earth getting warmer, or cooler?

Remarkable Information

Satellites don't measure latitudes above 82.5N or below 70S at all (as your link shows ! remember the map is a projection !) , GISTEMP analysis does include direct measurements south of 70S latitude, and interpolation estimates north of 82.5N latitude

StevenG - what was your response to my original point that there is very good agreement between all the datasets ? :-

http://tamino.files.wordpress.com/2007/08/global2.jpg

http://tamino.files.wordpress.com/2008/01/75-08.jpg

Bizzare ?

All the datasets seem to agree to me (and the slight difference between GISS and the rest is accounted for by the difference in interpolating data in polar regions)

Oh well, don't let the facts get in the way of a good story

see

http://tamino.files.wordpress.com/2007/08/global2.jpg

http://tamino.files.wordpress.com/2008/01/75-08.jpg

PS - copied from tamino's site :-

All these data are temperature anomaly. Anomaly is the difference between temperature at a given time, and the average temperature for the same time of year during some reference period. So temperature anomaly doesn’t really tell you, in absolute terms, how hot or cold it is — it tells you how much hotter or colder it is, than it was (on average) during the reference period. And there’s the rub: these data sets use different reference periods. GISS uses the reference period 1951 to 1980, HadCRU used 1961 to 1990, and the satellite estimates use 1979 to 2000. The coldest of these reference periods is the 1951-1980 GISS reference, the warmest is the 1979-2000 satellite reference. That means that GISS anomaly is the difference between present temperature and a colder time period, satellite data are the difference between present temperature and a warmer time period.

We can’t directly compare the numbers in a meaningful way without compensating for the difference in reference. Otherwise, it’s just like measuring my height in inches above Shaquille O’Neill (which makes the number quite negative) while measuring a newborn child’s height in inches above the ground (which makes the number certainly positive), noting that the infant’s number is greater, and concluding that the newborn is taller than I am. If we fail to compensate for the different reference, then we expect that the GISS numbers will be highest, the HadCRU numbers next, and the satellite data lowest. And that’s exactly what we observe.

Pretty basic, right? Anybody who pontificates about trends in temperature metrics, and compares different sources of data, really should know this, right?...