Amplification of Cretaceous Warmth by Biological Cloud Feedbacks
Lee R. Kump1* and
David Pollard2
The extreme warmth of particular intervals of geologic history
cannot be simulated with climate models, which are constrained
by the geologic proxy record to relatively modest increases
in atmospheric carbon dioxide levels. Recent recognition that
biological productivity controls the abundance of cloud condensation
nuclei (CCN) in the unpolluted atmosphere provides a solution
to this problem. Our climate simulations show that reduced biological
productivity (low CCN abundance) provides a substantial amplification
of CO
2-induced warming by reducing cloud lifetimes and reflectivity.
If the stress of elevated temperatures did indeed suppress marine
and terrestrial ecosystems during these times, this long-standing
climate enigma may be solved.
2 Earth and Environmental Systems Institute, Pennsylvania State University, University Park, PA 16802, USA.
* To whom correspondence should be addressed. E-mail: lkump{at}psu.edu
