How does rising atmospheric CO2 affect marine organisms?

Click to locate material archived on our website by topic

The Roman and Medieval Warm Periods in the Southern Austrian Alps
Schmidt, R., Kamenik, C. and Roth, M. 2007. Siliceous algae-based seasonal temperature inference and indicator pollen tracking ca. 4,000 years of climate/land use dependency in the southern Austrian Alps. Journal of Paleolimnology 38: 541-554.

What was done
The authors combined spring and autumn temperature anomaly reconstructions based on siliceous algae and pollen tracers found in a sediment core extracted from an Alpine lake (Oberer Landschitzsee; 4714'52" N, 1351'40" E) located at the southern slopes of the Austrian Central Alps just slightly above the present tree-line, in order to develop a 4000-year climatic reconstruction that they subsequently compared with (1) a similar time-scale reconstruction from another lake in the drainage area, (2) local historical records, and (3) other climate proxies on Alpine and Northern Hemispheric scales.

What was learned
Of most interest to us was Schmidt et al.'s finding that "spring-temperature anomalies during Roman and Medieval times equaled or slightly exceeded [our italics] the modern values and paralleled tree-line and glacier fluctuations," indicative of their broad range of applicability. As for the timing of the Medieval Warm Period, they identified "warm phases similar to present between ca. 850-1000 AD and 1200-1300 AD," which they say were "followed by climate deterioration at ca 1300 AD, which culminated during the Little Ice Age." Hence, their data place the Medieval Warm Period as occurring between AD 850 and 1300.

What it means
Schmidt et al. say that "temperature reconstructions from different proxies of the so-called Medieval Warm Period in relation to present global warming are controversial," acknowledging the difference of opinion that exists between climate alarmists, who contend that current temperatures are higher than they have been for the past two millennia or more (due to anthropogenic CO2 emissions), and climate skeptics such as us, who feel that both the Roman and Medieval Warm Periods were likely just as warm as, or even warmer than, it is currently (due to something other than CO2). In light of these facts, it would appear that Schmidt et al. had absolutely no problem describing their results in a way that jibes with our beliefs, perhaps because of the fact that a wealth of diverse data from all around the world are beginning to suggest the very same thing, as evidenced by the ever-growing mountain of evidence that is archived, one new study per week, in our Medieval Warm Period Project.

Reviewed 9 January 2008