Are we certain that trace amounts of CO2 are the major driver of ice conditions near the Antarctic Peninsula?

Deception Island: Information from Answers.com

Deception Island is an island in the South Shetland Islands off the Antarctic Peninsula which has one of the safest harbours in Antarctica. A recently active volcano, its eruptions in 1967 and 1969 caused serious damage to the scientific stations there.
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Deception Island exhibits some wildly varying microclimates. Some water temperatures reach 70°C (158°F). Near volcanic areas, the air can be as hot as 40°C (103°F).