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Climatologist Dr. Judith Curry rips UN IPCC’s ‘expert judgement’ that humans are ‘extremely likely’ responsible for more than half of warming since 1951

The IPCC does not have a convincing explanation for:

  • warming from 1910-1940
  • cooling from 1940-1975
  • hiatus from 1998 to present

The IPCC purports to have a highly confident explanation for the warming since 1950, but it was only during the period 1976-2000 when the global surface temperatures actually increased.

The absence of convincing attribution of periods  other than 1976-present to anthropogenic forcing leaves natural climate variability as the cause – some combination of solar (including solar indirect effects), uncertain volcanic forcing, natural internal (intrinsic variability) and possible unknown unknowns.

A key issue in attribution studies is to provide an answer to the question:  When did anthropogenic global warming begin?  As per the IPCC’s own analyses, significant warming didn’t begin until 1950.