The
atmospheric burden of carbon
dioxide (CO2) and methane (CH4) has been steadily increasing since the
start of the industrial age. The observed increases, illustrated
below, are
undoubtedly due to human activities. While increasing CO2 warms the
lower atmosphere
(the greenhouse effect), it cools the upper atmosphere through enhanced
radiative loss to space. Oxidation of CH4 in the stratosphere
produces H2O, which subsequently diffuses into
the upper atmosphere. Since NLCs are controled by temperature and
humidity, enhanced NLC activity provides is likely related to global
atmospheric change.
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