Why has global temperature been increasing since 1980 while solar activity has been decreasing?
A paper by Javier, edited by Andy May at WUWT.
The answer is that solar variability has multiple effects on climate with different time lags. Total Solar Irradiation variability has a direct effect on temperature within 0-2 years of ~ 0.2 °C (Tung & Camp, 2008) for the 11-year solar cycle. This is the effect accepted by all. The stratospheric effect of UV solar variability influences the North Atlantic oscillation that is lagged by 2-4 years (Scaife et al., 2013). Kobashi et al. 2015 describe a 10-40-year lag on Greenland temperature from ice cores that they attribute to the slowdown of the Atlantic Meridional Overturning Circulation and correlates with changes in the wind stress curl in the North Atlantic with a lag of 38 years in solar variability. Several studies correlating changes in tree-ring width and solar variability document a 10-20-year lag (Eichler et al., 2009; Breitenmoser et al., 2012; Anchukaitis et al., 2017).
The existence of multiple lags means that for the full effect of solar variability to be felt on climate there is a delay of ~ 20 years. The delay is due to the recruitment of slower changing atmospheric and oceanic climatic responses.
This means two things:
- Changes over the 11-year cycle are too fast to have much impact on climate.
- The general decline in solar activity since 1980 has been felt on climate from ~ 2000, and the low solar activity of SC24 should have a maximum effect on climate ~ 2035.
The evidence suggests that solar variability strongly influences climate change. The solar-hypothesis makes very clear predictions that are the opposite of predictions from the CO2-hypothesis. Regardless of changes in CO2 levels and emissions, the world should not experience significant warming for the period 2000-2035, and might even experience some cooling. If the prediction is correct we can assume that the solar contribution to climate is stronger than the CO2 contribution. Then more warming should take place afterwards.
Full Paper and Comments HERE.