
31The Fifth Revolution
conditions at very high latitudes, precipitation at somewhat lower latitudes
can change from snow to rain if the local temperature increases, resulting
in a decrease of snow cover. The extent (area) of snow cover in the Northern
Hemisphere has decreased by about 10% over the past century (Solomon
et al., 2007).
Sea level has been increasing over the past 150 years after remaining more
or less constant for thousands of years after the end of the last glacial cycle
(Figure1.25). So far, much of the increase is attributed to the warming and
thermal expansion of the ocean water. Observations since 1961 show that
the averag ...