Environmental Engineering Reference
In-Depth Information
Figure 9.5
Generalized curve of sea level rise since the last ice age. MWP = meltwater pulse. MWP-
1AO, 19,000 years ago; MWP-1A, 14,600 to 13,500 years ago; MWP-1B, 11,500 to
11,000 years ago; MWP-1C, ~8,200 to 7,600 years ago. (National Aeronautics and Space
Administration)
documented and are not doubted by those who favor the effect of
human infl uences (fi gure 9.5).
Those favoring human activities as the cause of global climate change
believe that there are no astronomical factors strong enough to create
the warming the globe has experienced in the past 150 years. Critics
respond that there are indeed astronomical variables that are strong
enough.
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These include changes in the shape of the earth's orbit (eccen-
tricity) and the earth's tilt and precession, all of which affect the amount
of sunlight received on the earth's surface. The timescale of their varia-
tions is well known. Solar intensity (as indicated by sunspots) also varies
periodically, and NASA believes that was a key factor in causing the
“Little Ice Age” from the 1400s to the 1700s.
In 2003, an Israeli physicist and a Canadian geochemist proposed a
new climate driver.
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They envision slow movements of the solar system
through the Milky Way galaxy as controlling the cosmic rays that
bombard the earth's atmosphere. A reduction in cosmic radiation would
lessen cloud cover and earth's refl ectivity, warming the planet; the reverse
