HR: 0800h
AN: U21E-02    [Abstracts]
TI: Land Development Caused the Observed Climate Warming Over the Last 200 Years
AU: * Lewis, T J
EM: sgc_ltd@telus.net
AF: Sidney Geophysical Consultants, 1107 Maple Road, N. Saanich, BC V8L 5P5, Canada
AB: There are many processes that influence the heat budget at the earth's surface. In most locations, the temperature at the earth's surface is the upper boundary condition for conductive heat flow in the solid earth. Underground temperatures record past changes in the surface temperature, and show that it has changed locally, due to land development. Where forests were removed and not replaced, the ground surface has warmed by 1 to 2 K. The amount of water evaporated/ transpired near the surface is reduced by the deforestation, reducing the upward transport of heat. For coastal forests in British Columbia, the maximum change in upward heat flux above ground is 2.5 Wm^-2, averaged over a year. This is similar to the change attributed to so-called greenhouse gases, and should be considered in climate models. Changing the surface albedo and the amount of heat absorbed by greenhouse gases can produce the same effects as land development: increased surface temperatures and heat released into the atmosphere. However, warming produced by land development is very localized, producing abrupt changes in ground surface temperatures and, on a regional scale, differences in onset times of some warm periods. The increase in runoff from deforested areas also is in agreement with this process. Similarly, other types of land development reduce the amount of water at the ground surface, causing a permanent warming of the ground surface temperature. The total amount of warming caused by stopping all evaporation/transpiration on land is limited to 3 K.
DE: 1631 Land/atmosphere interactions (1218, 1843, 3322)
DE: 1632 Land cover change
DE: 1637 Regional climate change
DE: 8130 Heat generation and transport
SC: Union [U]
MN: 2009 Joint Assembly