Posts Tagged ‘proposition 06’

GHCN data

Monday, December 14th, 2009

I’ve been looking at the GHCN data as a possible replacement for/addition to the GSOD series. It’s mostly a set of monthly averages, though there is a 1.7gb lump of “daily” data (which, glancing at extracts, appears to have a huge number of missing entries).

The GHCN does appear to have better coverage of Africa and 1934, so it will be interesting to see how that affects the results.

Proposition 06: Probably False

Sunday, December 13th, 2009

A fairly simple check to see compare two years’ annual mean temperatures:

rmw42@pandora:~/NOAA$ cat Averages.txt | ./compareyears 1934 1998
12 stations had 1934 warmer than 1998
3 stations did not have 1934 warmer than 1998
15139 stations rejected for having insufficient data

As expected, 1934 is warmer, but there aren’t many stations that far back in the daily data – the daily records only start in 1929. This would need to be confirmed against the raw monthly GHCN figures, which are more complete for the ’30s.

The deltas are:

1.7F, 0.3F, 1.2F, 0.3F, 0.0F, -0.8F, 3.4F, -0.8F, -0.4F, 1.5F, 1.7F, 3.6F, 3.1F, 8.5F, 1.7F

These give a mean difference of +1.66F, median of +1.49F, and quartiles of +0.04F and +3.06F.

0.01C is 0.018F, which is less than the lower quartile, so at least 75% of the results (actually 80%) are greater than the claimed difference. 15 samples is about the minimum required to assume that a Gaussian approximation is valid, and these results strongly suggests that the claim is false, but more data would be helpful.

Provisional result: 1934 was warmer than 1998 by 0.8-0.9 degrees Celsius.

Proposition 06: 1934 vs 1998

Sunday, December 13th, 2009

Someone called iCowboy posted a comment on Iain Dale’s Diary saying:

1934 vs. 1998 – the difference is 0.01 Celsius between those two years, but the statistics definitely show that 1998 sits well within a warm period, 1934 was generally cooler.

in response to claims that 1934 was actually warmer than 1998.

Proposition:

1934 is (at most) 0.01 degree Celsius warmer than 1998

Methodology:

Scan through the station-year records, find any which cover both 1934 and 1998 with reasonably-complete (>90%) data and check the temperature difference between them.