A paper published today in Climate of the Past finds the low solar activity during the Dalton Minimum from 1780-1840 had a significant effect on climate and ocean heat content. According to the authors, “Global and hemispheric mean surface temperatures show a significant dependence on solar irradiance at λ [wavelengths] > 250 nm” and “Reduction of irradiance at λ [wavelengths] > 250 nm leads to a significant (up to 2%) decrease in the ocean heat content (OHC) between 0 and 300 meters in depth, whereas the changes in irradiance at λ [wavelengths] < 250 nm or in energetic particles have virtually no effect.”
The paper shows a ~16 x 10^22 Joule decrease in global ocean heat content from 0 to 100 meters during the Dalton Minimum, which by way of comparison is 3 times larger than the 5 x 10^22 Joule increase in global ocean heat content 0-100 meters over the past 55 years [Levitus et al 2012, figure 2]. The paper also shows a global surface temperature decrease of ~0.8C during the Dalton Minimum, by way of comparison about the same as the 0.7 – 0.8C global warming since the Little Ice Age ended in ~1850.
While many climate scientists claim small changes in solar activity cannot affect climate, this paper and many others demonstrate that these changes do significantly affect ocean heat content and surface temperature to similar or greater magnitudes as found during the 20th century.
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