How does rising atmospheric CO2 affect marine organisms?

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Remains of Midges Have Climate Tale to Tell ... If We Can Learn Their Language
Brooks, S.J. and Birks, H.J.B. 2001. Chironomid-inferred air temperatures from Lateglacial and Holocene sites in north-west Europe: progress and problems. Quaternary Science Reviews 20: 1723-1741.

What was done
Midges (Insecta: Diptera: Chironomidae) - the larval-stage head capsules of which are well preserved in lake sediments - are, in the words of the authors, "widely recognized as powerful biological proxies for inferring past climatic change." Hence, the authors are deeply involved in refining protocols for using them to reconstruct temperature histories of various locations. In this paper they report their progress and illustrate the application of their techniques to some sites in Scotland and Norway.

What was learned
Of most interest to us, and of most significance to the CO2-climate debate, are the authors' findings for Lochan Uaine, in the Cairngorms region of the Scottish Highlands. This lake, in their words, "is remote from human habitation and therefore any response of proxy indicators to climatic change [is] unlikely to be masked by the effects of anthropogenic environmental change in its catchment." Reconstructed temperatures for this region peaked at about 11C during what they refer to as the "Little Climatic Optimum" - which we typically call the Medieval Warm Period - "before cooling by about 1.5C which may coincide with the 'Little Ice Age'." These results, say the authors, "are in good agreement with a chironomid stratigraphy from Finse, western Norway (Velle, 1998)," where summer temperatures were "about 0.4C warmer than the present day" during the Medieval Warm Period. This latter observation also appears to hold for the present study, since the upper sample of the Lochane Uaine core, which was collected in 1993, "reconstructs the modern temperature at about 10.5C" which is 0.5C less than the 11C value the authors obtained from the Medieval Warm Period.

What it means
These findings contribute to the growing mountain of evidence indicative of the likelihood that the Medieval Warm Period - in contradiction of climate alarmist claims - was, in fact, warmer than what it is currently, which suggests that the warming of the past century or so, as well as what might yet occur, is nothing more nor less than a natural return to the pleasant or "optimum" climatic conditions the world experienced well before the air's CO2 content began its historical ascent from what it was before the Industrial Revolution, which pretty much leaves CO2 out of the picture as far as its being the cause of the recent warming.

Grove, J.M. 1988. The Little Ice Age. Methuen, London.

Velle, G. 1998. A paleoecological study of chironomids (Insecta: Diptera) with special reference to climate. M.Sc. Thesis, University of Bergen.

Reviewed 23 January 2002