Climate is a major factor in the habitat, food chains, competition, success
and survival of species. Contemporary distributions and abundance of
marine species and communities reflect adaptation to geologically recent
climatic conditions and the impacts of human activities. Warming of the
atmosphere and seawater has occurred in association with increasing levels
of atmospheric carbon dioxide since the start of the twentieth century.
Despite continuing scientific research and wider discussion of the relative
roles of anthropogenic greenhouse gas increases and other influences on
climate, climate change is occurring. The policy and legal issues have two
core components: response to the effects of climate change, and addressing
the human activities for which there is reasonable evidence of causation or
exacerbation of climate change. For the purpose of this chapter, the focus
will be on the response to the effects of climate change, rather than on the
issue of anthropogenic causation and exacerbation.