ESS11
Prof.
Jin-Yi Yu
Natural Factors of Radiative Forcing
qSince
the late 1970s, satellite instruments have observed small oscillations due to the 11-year solar
cycle. Mechanisms for the amplification of solar effects on climate have
been proposed, but currently lack a rigorous theoretical or
observational basis.
qStratospheric aerosols from explosive
volcanic eruptions lead to negative forcing, which lasts a few years. Several major eruptions
occurred in the periods 1880 to 1920 and 1960 to 1991.
qThe
combined change in radiative forcing of the two major natural
factors (solar variation and volcanic aerosols) is estimated
to be negative for the past two, and possibly the past four,
decades.