(Part of the How to Talk to a Global Warming Skeptic guide)

Objection: Today’s warming is just a recovery from the Little Ice Age.

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Answer: This argument relies on an implicit assumption that there is a particular climatic baseline to which the earth inexorably returns — and thus that a period of globally lower temperatures will inevitably be followed by a rise in temperatures. What is the scientific basis for that assumption?

There is no evidence of such a baseline. The climate is influenced by many factors, which change or remain stable in their own ways. The current understanding of the Little Ice Age is that it was likely the result of a decrease in solar irradiance combined with an increase in volcanic activity, blocking additional sunlight. The LIA was also not particularly well synchronized globally, affecting different regions at different times. Scientists are aware of no century-scale pattern in solar output or volcanic activity, so there’s no reason to expect a reversal of those changes. As it happens, solar output did increase somewhat in the early 20th century, which did contribute to warming at that time. However, that’s not behind current warming.

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Another problem with appealing to a natural recovery from the LIA is that temperature has now risen to levels higher than the assumed baseline climate. So even if some recovery were to be expected, why have we now exceeded it? This argument has problems similar to the more general “it is part of a natural cycle” argument.