  We consider estimation of quantile curves for a general class of
nonstationary processes. Consistency and central limit results are obtained for
local linear quantile estimates under a mild short-range dependence condition.
Our results are applied to environmental data sets. In particular, our results
can be used to address the problem of whether climate variability has changed,
an important problem raised by IPCC (Intergovernmental Panel on Climate Change)
in 2001.
