How does rising atmospheric CO2 affect marine organisms?

Click to locate material archived on our website by topic

250 Years of Drought in East Central Sweden
Linderholm, H.W. and Molin, T. 2005. Early nineteenth century drought in east central Sweden inferred from dendrochronological and historical archives. Climate Research 29: 63-72.

What was done
Climate model simulations for Scandinavia suggest CO2-induced global warming will result in considerably drier summers over this region of Europe in the future (Swedish Regional Climate Modelling Programme, SWECLIM; If correct, such summer droughts could have severe impacts on agricultural and water supplies and significantly influence the economy of the region. To set these potential consequences in a long-term historical context, as well as to evaluate the validity of such claims, it is necessary to understand how summer precipitation has varied naturally over a long time scale. In the present study, Linderholm and Molin do just that by analyzing two independent precipitation proxies, one derived from tree-ring data and one from a farmer's diary, to produce a 250-year record of summer (Jun-Aug) precipitation in east central Sweden.

What was learned
Results of the researchers' analysis reveal there has been a high degree of variability in summer precipitation on inter-annual to decadal time scales throughout the record, with the past century exhibiting less variability than the 150 years that preceded it. One period that stands out vividly is a persistent dry episode in the early 1800s. Between 1806 and 1832, the tree-ring reconstruction reveals its longest consecutive period of below-average tree growth, which is associated with a concomitant period of drought that is documented in the farmer's diary.

What it means
If model predictions of increased summer drought associated with CO2-induced global warming are correct, we should expect to see some proof of this prediction in climate reconstructions of the past quarter of a millennium, for it is claimed by climate alarmists that over the last century of this period, the planet warmed at a rate that carried it to a temperature that was unprecedented over the past entire millennium. Yet, as the records reconstructed by Linderholm and Molin clearly indicate, summer drought in east central Sweden during the 20th century was less variable and less severe than at earlier times in the historical record, when it was considerably colder than it is today. Once again, therefore, we have another example of the models even missing the mark of mediocrity.

Reviewed 1 March 2006