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Nitrous Oxide
In this unit we examine another trace gas in the
atmosphere whose concentrations are observed to be increasing. Nitrous oxide,
, is a colorless, odorless, non-reactive gas that is very stable in
the troposphere (lifetime of 110-168 years). It should not be confused
with , NO, or other oxides of nitrogen. Nitrous oxide concentrations
have been steadily increasing with time, as shown in Figure 1a
which reports measurements at
several locations since 1977. It is important to note that the units of these measurements are
parts per billion by volume (ppbv). Nitrous oxide concentrations then are about one fifth of
methane concentrations and about a thousand times smaller than carbon dioxide.
Data over a longer time scale as derived from ice cores show that over the last 2,000 years nitrous oxide concentrations were nearly constant at about 280 ppbv until about the beginning of the Industrial Revolution, at which time there began a fairly dramatic increase which continues today at about 0.2 to 0.3% per year.
