Climate Change and Human Health: Risks and Responses

There is now widespread consensus that the Earth is warming at a rate unprecedented
during post hunter-gatherer human existence. The last decade was the
warmest since instrumental records began in the nineteenth century, and contained
9 of the 10 warmest years ever recorded. The causes of this change are
increasingly well understood. The Third Assessment Report of the Intergovernmental
Panel on Climate Change, published in 2001, goes further than its predecessors,
stating that “There is new and stronger evidence that most of the warming
observed over the last 50 years is likely to be attributable to human activities”, most
importantly the release of greenhouse gases from fossil fuels.
Stresses on the climate system are already causing impacts on Earth’s surface.
These include not only rising surface temperatures, but also increasingly frequent
floods and droughts, and changes in natural ecosystems, such as earlier flowering
of plants, and poleward shifts in the distribution of several species. All of
these changes are inextricably linked to the health of human societies. Climatic
conditions affect human well-being both directly, through the physical effects of
climatic extremes, and indirectly, through influences on the levels of pollution
in the air, on the agricultural, marine and freshwater systems that provide food
and water, and on the vectors and pathogens that cause infectious diseases.
As it is now widely accepted that humans are influencing global climate, decision
makers are now focusing on the type and timing of actions to limit the rate
of change. Attention is shifting to the balance between the possible impacts of
climate change, and the economic costs, technological advances and societal
adaptations that are necessary for mitigation.
International agreements, supported by hard science, are proving effective in
combating wide-ranging environmental threats such as ozone depletion and
long-range transboundary air pollution. Can similar agreements be implemented
to address the more complex risks posed by global climate change? Scientific
analysis in general, and the health sector in particular, need to inform and help
advance ongoing policy discussions. Firstly, the scientific community must
produce rigorous and balanced evidence not only of the breadth and magnitude
of climate change effects, but also of how they are distributed across populations,
and over time. Just and equitable decisions on appropriate responses to climate
change can only be reached by giving consideration to all those affected by policy
actions (or inactions), including future generations. Secondly, as some degree of
continued climate change is now inevitable, it is necessary to identify vulnerable
populations, and formulate policies and measures to help them adapt to
changing conditions.
This book, prepared jointly by the World Health Organization, the World
Meteorological Organization and the United Nations Environment Programme, works towards these ends. It provides a comprehensive update of a previous
review, published in 1996. More importantly, it expands the scope of the review
to include quantitative estimates of the total health impacts of climate change.
It lays out the steps necessary to further scientific investigation and to develop
strategies and policies to help societies adapt to climate change.