energy budget is maintained, storminess helps to moderate extreme surface tem-
peratures by forcing horizontal and vertical mixing. (5) Elevation is well corre-
lated with various weather elements like pressure, moisture and temperature
which all decrease with altitude. Significant altitudinal differences make for differ-
ent climates in adjacent, whether or not there are mountains present. (6) Topo-
graphic blockage is the effect of surface weather unable to bypass ranges of
mountains and large hills. The climates can be quite different on the different sides
of the topographic impediments. For instance, the frigid wintertime Siberian air is
unable to pass over the Tibetan Plateau with an average elevation of 4,500 m
(14,000 ft) and the Indian Subcontinent to its south enjoys a mild winter.
Vladimir Ko ̈ppen (1846–1940) was first to numerically regionalize climate thus
revolutionizing climate science. His work was inspired by the world vegetation
maps then available; Ko ̈ppen attempted to fit numerical boundaries. More subtly,
his classification scheme of the early 20th century was made possible by the
increasing availability of climate-length weather records. After the middle of the
19th century, weather instruments had become standardized. Numerous world
cities boasted published climatological summaries. The summaries were mainly
temperature and precipitation averages. Ko ̈ppen used these two dimensions in con-
structing his classification system. In modified form, this classification has been
well used by geographers and other scientists for the last century. The Ko ̈ppen sys-
tem is a relatively simple system with which to understand the large regionalities
of Earth’s climate. It has continued appeal because of its correspondence withbio-
mesandsoilregions.60 Climate
Ice Shelves
In the polar lands are ice shelves that are permanent ice floating on the water while attached
to the land. The thickness of the shelf can be as much as 1,000 m (over 3,000 ft). Most ice
shelves are the result of the flow of glacial ice reaching the sea and continuing on because of
the gravity-cause movement of ice behind it and because ice floats on liquid water. The size
of an ice shelf depends on the amount and speed of flow of the glacial ice and theclimate
and water motion on the ocean. The age of ice shelf ice can reach to thousands of years in pla-
ces protected by coastal configurations. Ice shelves occur off of Canada’s Ellesmere Island and
off of mountain glaciers in North America and Eurasia. These areas of shelf ice pale in com-
parison to Antarctic ice shelves, the largest of which—the Ross Ice Shelf—approaches a half
million square kilometers (193,000 sq mi). Ice shelves do not affect sea level until their water
melts. In recent years, Antarctica has had notable collapses of ice shelves each occurring
within a few months. The largest was the disappearance of 8,000 sq km (3,100 sq mi) in two
months. Ice shelf disappearance may well be a signal of global warming.