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| The sunspot cycle length as a measure of the Sun's activity: Variation during the period 1861 - 1989 of the sunspot cycle length (solid curve) and the temperature anomaly of the Northern Hemisphere (dashed curve). The temperature data from the IPCC. |
Jasper Kirkby (1998) - The sunspot cycle length averages 11 years but has varied from 7 to 17 years, with shorter cycle lengths corresponding to a more magnetically-active Sun. A remarkably close agreement was found between the sunspot cycle length and the change in land temperature of the Northern Hemisphere in the period between 1861 and 1989 [update HERE]. The land temperature of the Northern Hemisphere was used to avoid the lag by several years of air temperatures over the oceans, due to their large heat capacity. This figure covers the period during which greenhouse gas emissions are presumed to have caused a global warming of about 0.6°C. Two features are of particular note: firstly the dip between 1945 and 1970, which cannot be explained by the steadily rising greenhouse gas emissions but seems well-matched to a decrease in the Sun's activity, and secondly the close correspondence between the two curves over this entire period, which would seem to leave little room for an additional greenhouse gas effect.
[...] The observation that warm weather seems to coincide with high sunspot counts and cool weather with low sunspot counts was made as long ago as two hundred years by the astronomer William Herschel who noticed that the price of wheat in England was lower when there were many sunspots, and higher when there were few. See also HERE
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| Data: SILSO Royal Observatory of Belgium. |