The 30-year ‘baseline’


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I first raised this issue some years ago (Davis, 2003) after noting that some temperature data were starting to be compared not with the long-established 1961–1990 ‘baseline’ but with the 1971–2000 period, and as a consequence any global-warming trends, from whatever cause, would be understated. My comment was politely dismissed and it was with some diffidence I raised the issue again recently – with, frankly, a similar outcome.

I remain uneasy that those involved mainly with forecasting, and hence the public's perception of the weather, are side-stepping the single most talked-about ‘weather’ topic in other fields, such as natural history: to what extent we are currently experiencing a long-term climatic trend and the impact such may have on nature. I was therefore gratified to see the recent supportive letter by Richard Probert-Jones (2012). This is a wide-ranging topic on which a professional journal such as Weather should surely take the broad view and be a reference source for informed debate.

I accept that 1961–1990 is an arbitrary baseline, but it does cover a period relatively early in the very rapid post-war massive increase in fossil-fuel use and corresponding CO2 emissions.