Posts Tagged ‘proposition 05’

Proposition 05: False or Undefined

Wednesday, December 9th, 2009

Well, that one was remarkably easy. Take the sorted annual mean recorded temperature and see if the top result is 1998:

rmw42@pandora:~/NOAA$ cat Averages.txt | ./topyear
1163 stations had their warmest year in 1998
4985 stations did not have their warmest year in 1998
9970 stations rejected for having insufficient data

That would be a “no”, then. 19% of stations report 1998 as their warmest year, which means 81% do not. Clearly the proposition is not true.

19% is quite a lot, though, and 1998 was clearly a very warm year. Is it likely that another year scores a much higher proportion? If not, the proposition is ill-defined: there is no such thing as a warmest year for the entire planet, as different parts are warm at different times. That’s different from the proposition being false – instead the proposition is meaningless.

Possible follow-up: what does the histogram of “warmest years” look like? Would need to be careful to take account of incomplete coverage… Similarly, the Mean Reciprocal Rank of a year would be interesting to see.

Propositions 03, 04, 05: Hot decade

Wednesday, December 9th, 2009

Today’s Metro article “China lambasts US and EU emission pledges” by Jo Steele contains a barrage of claims:

Meanwhile, the Noughties have been the warmest decade on record and this year has been one of the five hottest, weather experts warned.

While 1998 remains the hottest single year since records began in 1850, the last ten years have been the warmest, the Met Office revealed.

Wow. It ends with what looks like a repeat of (false) Proposition 02, but the others can stand a bit of scrutiny.

Proposition 03:

The Noughties have been the warmest decade on record

Proposition 04:

This year [2009] has been one of the five hottest [years on record]

Proposition 05:

1998 remains the hottest single year since records began

Methodology:

Well, propositions 04 and 05 seem fairly straightforward – top 1 and top 5s to go with the top 10 analysis already done. A bit of Perl hacking should get results for those today, though since we’re still in 2009 the final result will have to wait until January. Proposition 03 will take a bit more work, but not much – do we consider rolling decades or bucket the temperature record by (year/10)? Rolling decades is probably the more general version, but both are interesting tests to run.

So, time to get cracking!