New book finds at least 63% of global warming was due to the Sun — ‘Authors predict a decrease in solar activity during 21st century will result in global cooling of 0.64ºC over next 100 years’

Therefore, out of the total increase in global temperature of ~ 0.8ºC during the past 400 years, less than 0.3ºC may be of non-solar origin, in agreement with previous results.” The authors predict a decrease in solar activity during the 21st century will result in global cooling of 0.64ºC over the next 100 years.