Page 105 - Earth's Climate Past and Future
P. 105
CHAPTER 5
Greenhouse Climate
Earth’s geography is much easier to reconstruct for 100 Myr ago than it is for
earlier times. The positions of all the continents are known, as are the locations
of the edge of the sea along continental margins and the shapes of the ocean
basins. Regional and global average rates of seafloor spreading are also better
constrained. In addition, climate scientists know much more about Earth’s
climate 100 Myr ago, including the fact that it was warm enough at the South
Pole to keep ice sheets from forming. With this array of evidence, scientists can
ask an important question about this interval: Was this global warmth caused
by a high level of atmospheric CO ? The answer to this question potentially
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holds lessons about our climatic future in a world warmed by rising levels of the
same gases. Next, we explore the reasons why sea level 100 Myr ago was higher
than it is today and the effects of the higher sea level on climate. Finally, we
investigate the climatic and other environmental effects of a giant asteroid
impact 65 Myr ago during the later stages of warm greenhouse conditions.
