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The article says that evidence of past climate variations in Antarctica may invalidate global warming as a cause for the recent demise of several ice shelves in that area. Isn’t the length of time over which the changes occurred the critical thing? If the changes are occurring over roughly the same time span as they did in the past, then the recent changes can’t be used to substantiate global warming. On the other hand, if the changes are taking place much more quickly, then they are significant and must be accounted for. Which of these two scenarios is true in this case? John Jaros
Quakertown, Pa.
The researchers weren’t able to determine the precise rate of warming that led up to the ice-free period. Although greenhouse gases emitted since the beginning of the Industrial Revolution could be significantly influencing the rate of recent ice-shelf demise, the scientists say that the fact that there was open ocean in portions of the Antarctic since the end of the last ice age suggests that those gases aren’t the sole cause for melting ice. –S. Perkins