If you’re 27 or younger, you’ve never experienced a colder-than-average month
The United States National Oceanic and Atmospheric Administration (NOAA) released a usual monthly State of the Climate Global Analysis in October 2012 which was anything but usual. Buried in the report was this astounding factoid: “This is the 332nd consecutive month with an above-average temperature”. What that means is, if you’re 27 or younger, you’ve never experienced a colder-than-average month. I find that phenomenal, a trend which if it continues might allow many to become ‘old timers’ who can “recollect the ‘good old days’ when a monthly temperature could be below average” (i.e. prior to March 1985).
This statement is certainly headline-grabbing, although there is some devil in the detail. Specifically, what is the ‘average’ which the NOAA benchmark against? A bit of research reveals that the NOAA use a reasonably robust 3-decade (1981-2010) average for their graphics, but the phrasing of the paragraph in question suggests that in this case they are comparing to the 20th century average. If it was the 3-decade dataset then the months Jan 1981 – Feb 1985 would have had to have been exceptionally cold to skew the average so low that it could be exceeded 332 times consecutively.
The field of time series and calculating moving averages (and variabilities) is fascinating, and no doubt with sufficient data-mining, as in any field (imagine sporting statistics), a number of other shocking statistics could be extracted. Nonetheless a 332 month run is still impressive (or incredibly concerning). Interpretation of climate change will more and more require punters to be comfortable with interpreting both running averages and changing variabilities. We can have extremely cold snaps in a month (variability) while still having an above average month for temperature.