  Understanding the causes and consequences of, and devising countermeasures
to, global warming is a profoundly complex problem. Network representations are
sometimes the only way forward, and sometimes able to reduce the complexity of
the original problem. Networks are both necessary and natural elements of
climate science. Furthermore, networks form a mathematical foundation for a
multitude of computational and analytical techniques. We are only beginning to
see the benefits of this connection between the sciences of climate change and
network science. In this review, we cover the wide spectrum of network
applications in the climate-change literature -- what they represent, how they
are analyzed, and what insights they bring. We also discuss network data,
tools, and problems yet to be explored.
