Top Panel: Same as the third top panel in Figure 1.
Panel: A case considering only the changes in solar insolation.
Bottom Panel: Time series of natural factors given
to the model.
The yellow line shows the changes in solar insolation and the blue line
shows the effect of the aerosol reaching to the stratosphere due to a
large-scale volcanic eruption, which cools off the surface. Note that
these two are not for direct comparison since they shows different physical
The warming trend in the early 20th (1910 to 1945) century cannot be explained
only by the increase in solar insolation. Both gradual temperature rise
due to the increase in solar insolation and the recovery from the cooling
due to the volcanic eruption cause the warming trend concurrently.