David Archibald's latest review of solar activity and climate impacts concludes in part:
"5.
LONG TERM CORRELATION OF SOLAR ACTIVITY WITH CLIMATE
The aa Index is a geomagnetic activity index which is driven by the solar coronal
magnetic field strength. There are now 140 years of aa Index data, shown in Figure 9.
The strength of the solar coronal magnetic field doubled over the 20th century. At the
same time, the Earth came out of the Little Ice Age. The 1970s cooling period, during
Solar Cycle 20, was associated with a weak aa Index. During the current solar
minimum, the aa Index is likely to fall to levels last seen in the late 19th century.
Figure 10 shows an incontrovertible association between solar activity and climate.
The spikes in Be10 concentration coincide with the cold periods in Earth’s history for
the last 600 years. All the major climate minima are evident in the Be10 record,
including the cold period at the end of the 19th century.
What is also evident is that
Be10 levels started falling away dramatically at the beginning of the Modern Warm
Period, consistent with the warming of the 20th century being solar-driven.
6. PAST AND FUTURE WARMING FROM ANTHROPOGENIC CO2
Archibald (2007) illustrated the logarithmic warming effect of carbon dioxide.
The
first 20 ppm of carbon dioxide in the atmosphere has a greater warming effect than the
following 400 ppm (Figure 11). The increase in atmospheric carbon dioxide
concentration from the pre-industrial level of 280 ppm to the current level of 384 ppm
is calculated to have resulted in a 0.1° C rise in atmospheric temperature. If the
atmospheric carbon dioxide level increases to 600 ppm, a further 0.3° C increase in
temperature is projected due to this factor."
The full paper is worth the reading and available here:
http://www.davidarchibald.info/paper...ald2009E&E.pdf