How does rising atmospheric CO2 affect marine organisms?

Click to locate material archived on our website by topic

Past Temperatures in China
Zhuo, Z., Baoyin, Y. and Petit-Marie, N. 1998. Paleoenvironments in China during the Last Glacial Maximum and the Holocene Optimum. Episodes 21: 152-158.

What was done
The authors reviewed present knowledge of climatic conditions in China during the Last Glacial Maximum (approximately 18,000-22,000 years ago) and the Holocene Optimum (approximately 5,000-10,000 years ago).

What was learned
Compared to climatic conditions of today, mean annual temperatures during the Last Glacial Maximum were 7-10C colder than present in northern China and 4-6C colder in southern China, while annual precipitation totals ranged from 200 to 600 mm lower than present. At the other extreme, temperatures during the Holocene Optimum were 2-6C warmer than at present, resulting in the retreat of glaciers across the country, some of which disappeared altogether in eastern China. Warmer temperatures during this time period also resulted in a retreat of the southern permafrost limit to 100 km north of its current location. The Holocene Optimum was also a wetter time, with annual precipitation values 50-400 mm higher than at present.

What it means
This paper summarizes a broad range of studies that demonstrate that earth's climate was considerably warmer at a time, just a few thousand years ago, when the air's CO2 concentration was fully 100 ppm lower than at present, revealing yet again that there is no compelling reason to ascribe the approximate 0.5C temperature rise of the 20th century to greenhouse gas-induced global warming.

Reviewed 15 February 1999