  This paper describes some of the astronomical effects that could be important
for understanding the ice ages, historic climate changes and the recent
temperature increase. These include changes in the sun's luminosity, periodic
changes in the earth's orbital parameters, the sun's orbit around our galaxy,
the variability of solar activity and the anticorrelation of cosmic ray flux
with that activity. Finally recent trends in solar activity and global
temperatures are compared with the predictions of climate models.
