Precipitation - steady as she goes
Dec 4, 2015
Bishop Hill in Climate: other

A new paper by van Wijngaarden and Syed in the Journal of Hydrology notes a claim by the IPCC:

...the IPCC has reported that precipitation increased in some regions by as much as 1% in each decade of the 20th century.

The paper's authors then set about testing this claim.

The percentage annual precipitation change relative to 1961–90 was plotted for 6 continents; as well as for stations at different latitudes and those experiencing low, moderate and high annual precipitation totals. The trends for precipitation change together with their 95% confidence intervals were found for various periods of time. Most trends exhibited no clear precipitation change. The global changes in precipitation over the Earth’s land mass excluding Antarctica relative to 1961–90 were estimated to be: 1.2 ± 1.7, 2.6 ± 2.5 and 5.4 ± 8.1% per century for the periods 1850–2000, 1900–2000 and 1950–2000, respectively. A change of 1% per century corresponds to a precipitation change of 0.09 mm/year.

So if my maths is correct, the IPCC is out by as much as an order of magnitude. Perhaps the regions they were testing were smaller.

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