  Herein we show that the historical records of mid-latitude auroras from 1700
to 1966 present oscillations with periods of about 9, 10-11, 20-21, 30 and 60
years. The same frequencies are found in proxy and instrumental global surface
temperature records since 1650 and 1850, respectively and in several planetary
and solar records. Thus, the aurora records reveal a physical link between
climate change and astronomical oscillations. Likely, there exists a modulation
of the cosmic ray flux reaching the Earth and/or of the electric properties of
the ionosphere. The latter, in turn, have the potentiality of modulating the
global cloud cover that ultimately drives the climate oscillations through
albedo oscillations. In particular, a quasi 60-year large cycle is quite
evident since 1650 in all climate and astronomical records herein studied,
which also include an historical record of meteorite fall in China from 619 to
1943. These findings support the thesis that climate oscillations have an
astronomical origin. We show that a harmonic constituent model based on the
major astronomical frequencies revealed in the aurora records is able to
forecast with a reasonable accuracy the decadal and multidecadal temperature
oscillations from 1950 to 2010 using the temperature data before 1950, and vice
versa. The existence of a natural 60-year modulation of the global surface
temperature induced by astronomical mechanisms, by alone, would imply that at
least 60-70% of the warming observed since 1970 has been naturally induced.
Moreover, the climate may stay approximately stable during the next decades
because the 60-year cycle has entered in its cooling phase.
