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Hurricanes
Effects of Global Warming
Hurricanes
are affected by a wide range of factors, however the two most important
factors
in determining the potential intensity of a hurricane are sea surface
temperature (SST) and the temperature at the storm top.
The equation for maximum wind velocity is as
follows (Emanuel, 1999):
Graph
2: The part of the equation that is circled in red is the part that we
are
concerned about. It means that climate
temperature affects potential hurricane intensity through the
difference
between absolute SST and absolute temperature at the storm top (upper
troposphere to lower stratosphere) divided by the latter.
Therefore if climate change causes SST to
rise faster than atmospheric temperature, potential wind velocities
should
increase, and, therefore, potential hurricane intensity should increase
as
well. This discrepancy between the rate
of change of SST and the rate of change of atmospheric temperature (in
the
vicinity of the height of the storm top) has been observed in a careful
analysis by Kerry Emanuel. This is
corroborated by the Board of Atmospheric Sciences and Climate (2000). As hurricanes reach
higher intensities, the time it takes for them to build up to those
higher
intensities and then to dissipate will have increased from that of
lower
intensity hurricanes (Emmanuel, 2005).
Whether
or not a changing climate is affecting or will affect the
frequency of hurricanes is extremely controversial at the moment. While it is important to know whether the
frequency of hurricanes will increase or not (the more hurricanes there
are,
the more there are that could potentially make landfall), there isn’t
enough
data available to predict whether or not there is a trend in hurricane
frequency. Even if there is a trend,
there is not enough data to link it (or not link it) to global warming (Trenberth, 2005).