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Abstract:
The impacts of global climate change on different aspects of humanity’s diverse life-support systems are complex and often
difficult to predict. To facilitate policy decisions on mitigation
and adaptation strategies, it is necessary to understand, quantify,
and synthesize these climate-change impacts, taking into account
their uncertainties. Crucial to these decisions is an understanding
of how impacts in different sectors overlap, as overlapping
impacts increase exposure, lead to interactions of impacts, and
are likely to raise adaptation pressure. As a first step we develop
herein a framework to study coinciding impacts and identify regional
exposure hotspots. This framework can then be used as
a starting point for regional case studies on vulnerability and multifaceted
adaptation strategies. We consider impacts related to
water, agriculture, ecosystems, and malaria at different levels of
global warming. Multisectoral overlap starts to be seen robustly at
a mean global warming of 3 °C above the 1980–2010 mean, with
11% of the world population subject to severe impacts in at least
two of the four impact sectors at 4 °C. Despite these general conclusions,
we find that uncertainty arising from the impact models
is considerable, and larger than that from the climate models. In
a low probability-high impact worst-case assessment, almost the
whole inhabited world is at risk for multisectoral pressures. Hence,
there is a pressing need for an increased research effort to develop a more comprehensive understanding of impacts, as well as for the development of policy measures under existing uncertainty.
