How does rising atmospheric CO2 affect marine organisms?

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Naychhudwari Bog, Himachal Pradesh, India
Chauhan, M.S. 2006. Late Holocene vegetation and climate change in the alpine belt of Himachal Pradesh. Current Science 91: 1562-1567.

Chauhan analyzed pollen profiles derived from a 1-m-deep sediment core retrieved from Naychhudwari Bog (7743'E, 3230'N), Himachal Pradesh, northern India. Distributions of the different types of pollen revealed two broad climatic episodes of warm-moist and cold-dry conditions, the first covering the period AD 650 to 1200 and the second from AD 1500 onwards. "In the global perspective," to quote the author, the first period "is equivalent to the Medieval Warm Period, which has been witnessed in most parts of the world [our italics]," while the second period "falls within the time-limit of [the] Little Ice Age." In addition, Chauhan states that from AD 1500 onwards "the glaciers advanced and consequently the tree-line descended under the impact of [the] cold and dry climate in the region," which suggests that (1) the region has not yet become as warm as it was during medieval times, or (2) if such a level of warmth has been achieved, its temporal existence falls far short of that of the much longer sustained warmth of the Medieval Warm Period, or (3) both of the above.