According to the 1990 IPCC Report, an additional 0.5C global warming would need to be observed before natural variability could be distinguished with high confidence from an "enhanced greenhouse effect" due to man-made emissions. However, as an article today at Reason.com points out,
"...enhanced greenhouse warming above the noise of natural climate variability would not yet have crossed over the benchmark (+0.5°C) set by the IPCC back in 1990. Interesting."Satellite data indicates only ~0.2C warming since 1990, considerably short of the 0.5C threshold the IPCC set for itself in 1990 to determine whether additional global warming was within natural variability.
The activist-IPCC of today conveniently discarded these goalposts, and unjustifiably claims (without any statistical basis) 95% confidence that "most" global warming since 1950 is man-made.
|RSS satellite data show only 0.2C global warming since 1990, considerably short of the 1990 IPCC threshold of an additional 0.5C warming to detect an anthropogenic "enhanced greenhouse effect"|
|Warming since the beginning of the HADCRU3 global temperature record in 1850 is only ~0.8C, short of the 1990 IPCC threshold [1C since the late 19th century] to detect an anthropogenic "enhanced greenhouse effect"|