Scales of Climate in Designing with the Desert - Design with the Desert: Conservation and Sustainable Development - page 60

TABLE 3.3
Global Climate Model Estimates for the Colorado Basin at Various
Years in the Future

Temperature
Change

Precipitation
(%)

Runoff
(%)

Reservoir
Storage (%)

Hydropower
Production (%)

CTRL +0.9 −1 −10 −7 −16

Period 1 +1.8 −3 −14 −36 −56

Period 2 +3.1 −6 −18 −32 −45

Period 3 +4.9 −3 −17 −40 −53

CTRL is a control run based on 1995 greenhouse emissions. Temperature is in °F.
Periods 1, 2, 3 are so-called Business as Usual increases in emission scenarios projected
for years 2010-2039, 2040-2069, and 2070-2098. Business as Usual assumes no
addressing of increased greenhouse gas emissions. For downscaling procedures and
model constructs, see Christensen. 8

climate network in the country because of the stimulus of global change and the need to
envision scenarios of the future.
Recent assessment of the world's future climate is contained in the U.S. Global Climate
Program reports by region of the country, 7 in many publications, * and in the more recent
Intergovernmental Panel on Climate Change Assessment (IPCC4). 5 As an example, Table
3.3 illustrates general scenarios for the Colorado River Basin due to global climate change
in the future. 8 The results point to a future climate of warming temperatures, less precipi-
tation and decreased runoff, and storage and hydropower in the Colorado Basin over time
in the twenty-first century. In a more local study 9 for the Salt-Verde Watershed of central
Arizona, a 6.7°F warming is projected and a decrease of 0.1 in. per month precipitation,
yielding a scenario of over 15% less runoff from the watershed by mid-century. It should
be emphasized that these are scenarios and not precise predictions, and there is much
uncertainty involved, especially for smaller-scale systems such as the Southwest monsoon
and summer precipitation. Nevertheless, these scenarios may sway decision makers to
become aware that planning strategies used during the last 100 years (based on historical
variations) may not sustain us for the next 100 years because a major shift in the climate
system has a better than random chance of occurring. 9

3.3 Regional Scale
The regional scale in climatology spans a considerable range of space, such as continental,
suboceanic regions (e.g., areas of contiguous ocean temperatures), plains, plateaus,
mountains, broad basins, watersheds, earth biome regions, and often what is classified on
world climate maps as earth's climate regions (tropical rain forest, savanna, desert, steppe,
humid subtropical, marine west coast, Mediterranean, humid continental, subarctic,
tundra, ice cap). The dynamic processes that create these differences are many. It should
be emphasized that the majority of the explanations of regional climate relate first of all to

* See, for example, Stott et al. 5 and Christensen et al. 8