The prospect of global climate change affecting patterns of human health poses
a central challenge to scientists and policymakers. For scientists, the causation
of most of the health outcomes considered in this chapterfrom respiratory
and cardiovascular disease to various types of infectious diseasesis complex:
Various social, technological, demographic, behavioral, and environmental factors
influence the risk of occurrence of these diseases. For that reason, it will
remain difficult in the near future to identify any early impacts of the current
climate trends on health. This complex causation of human disease also means
that predictive modeling of future climatic impacts should take realistic account
of the coexistent and modulating effects of nonclimate factors.
Over the past 5 years, we have acquired better understanding of direct temperature
effects on health (heat and cold), temperature effects on air pollutant production,
the seasonality of certain infectious diseases, and the public health consequences
(and situational modifiers) of extreme weather events. Predictive modeling of
how scenarios of future climate change would affect the patterns and impacts
of vector-borne diseases has evolved, as has modeling of impacts on regional
agricultural yields and the geography of world hunger.
Policymakers should appreciate that although our scientific capacity to foresee
and model these various health outcomes of climate change continues to evolve,
it is not possible to make precise and localized projections for many health
outcomesespecially those that result indirectly from a sequence of impacts.
In the meantime, a precautionary approach requires that policy development proceed
on the basis of the availablethough often limited and qualitativeevidence
of how climate change will affect patterns of human population health. Furthermore,
high priority should be assigned to improving the public health infrastructure
and developing and implementing effective adaptation measures.