Programs
Med School Education
Requirements
Bibliography
Contact Info
Course Password
Topics
Introduction
Ecological
Biodiversity
Climate Change
Oceans
Living Sea
Environmental Challenges
Harvard Research and Response
Food
Community Health
Solutions
New Alliances
2006 Course
Lecture Archive
Education Program
Policy Maker Education
Sustaining Life
Climate Change Futures
Healthy Ocean, Healthy Humans
Healthy and Sustainable Food
Scientists and Evangelicals Initiative
Archives
Address:
Harvard Medical School
401 Park Drive, 2nd Floor East
Boston, MA 02215
Tel: 617.384.8530
Fax: 617.384.8585
General Email Address
Directions
|
|
The Changing Climate: Summaries
- The Science of Climate Change
James J. McCarthy, PhD, Harvard University
Within the last four decades evidence that Earth's climate is changing at an unusual rate has drawn the attention of scientists who endeavor to understand how the physical, chemical, and biological aspects of climate are linked. Our species, Homo sapiens, has altered many fundamental aspects of the climate system, most notably the composition of Earth's atmosphere. Over the last several million years, climate fluctuations were driven by basic properties of Earth - Sun orbital geometry, and over shorter periods, by lags in the response of atmospheric and ocean circulation, solar variability, volcanic activity and by the functioning of the biosphere. Changes in the atmospheric concentration of greenhouse gases resulting from human activities now have the potential to swamp these natural changes. The fundamental physical and chemical aspects of these processes are known, but important details, especially the moderating and enhancing properties of biological processes, are still only poorly quantified.
Greenhouse gases are now at higher concentration in the atmosphere than at any time in the last million or more years. Should we be concerned? This enhanced "insulation" in the lower atmosphere will continue to warm the surface of Earth, evaporate more water, and energize the atmosphere. How much difference will this make in Earth's climate, and how much of this change might we be prepared to live with?
Certain recent climate trends are difficult to ignore.
The 1980s and then the 1990s were the warmest decades in the last century. Is it particularly surprising that precipitation anomalies of unprecedented magnitude occurred on the Indian subcontinent (Bangladesh) in 1998, Central America (Honduras) in 1998, and South America (Venezuela) in 1999? What about changes in the Arctic with widespread melting of permafrost and Arctic Ocean sea ice (40 % has been lost in the last forty years)?
Inertia in both the Earth's climate system and human socioeconomic systems preclude an immediate cessation to this warming in any plausible future. Hence, climate is likely to continue to change for the next several human generations, resulting in some positive and some negative effects for different human and natural systems. However, the rate of future climate change can be minimized, and doing so will reduce harm to the most vulnerable individuals and communities.
Whether we are discussing past, present or future climate regimes, many unknowns remain relating to the intricacies of interactions within the climate system, However, the greatest uncertainty as to how climate will behave in the future depends on how humans will actually behave. How many of us will there be? What will be our standard of living in the developed and in the developing world? And, very importantly, how fossil fuel intensive will these development activities be?
- Climate Change and Health
Paul R. Epstein, MD, MPH, Harvard Medical School
Climate change has multiple direct and indirect consequences for human health. Heatwaves are the most direct and are projected to take an increasing toll in developed and underdeveloped nations. The 2003 summer heatwave in Europe, with 35,000 excess deaths in five nations, extensive wildfires and widespread crop failures demonstrates that climate change and the magnitude of its impacts may be surprisingly non-linear.
Climate also restricts the range of infectious diseases, while weather affects the timing and intensity of outbreaks. The ranges of several key diseases or their vectors are already changing in mountainous regions, along with upward shifts in plant communities, the rapid retreat of alpine glaciers and an upward shift in the freezing isotherm (the level at which temperatures remain below freezing all year).
Deep ocean warming is accelerating the hydrological cycle and the associated extreme weather events (EWEs) can create conditions conducive to outbreaks of infectious diseases. Heavy rains can leave insect breeding sites, drive rodents from burrows and contaminate clean water systems. Conversely, drought can spread fungal spores, spark fires (and respiratory illness) and is statistically associated with large outbreaks of West Nile virus and St Louis encephalitis, a disease with a similar life cycle.
Sequences of extremes can destabilize predator/prey relationships, leading to population explosions of opportunistic, disease-carrying organisms (e.g., rodents and mosquitoes). The 1997/98 El Niño-related extreme weather events spawned "clusters" of disease outbreaks in many regions of the globe.
In the marine environment, ocean warming – along with eutrophication and loss of filtering wetlands -- is contributing to harmful algal blooms that can cause shellfish poisoning, provide a reservoir for cholera and other bacteria, and can lead to hypoxia and "dead zones".
Excess carbon dioxide itself has consequences for organisms. Ragweed grown in elevated carbon dioxide levels produces a lot of pollen. Opportunistic, weedy plants take advantage by allocating CO2 to reproduction - the male parts - whereby they spread and prosper. Pioneering trees that spread quickly - like maples, pines, birches, and poplars - also appear to be boosting their seeds, cones, and pollen.
The impacts of EWEs also have economic consequences. Yearly losses increased from $4 billion annually in the 1980s to $40 billion in the 1990s; reached $55 billion in 2002 ($11 billion insured) and $60 billion ($15 billion insured) in 2003. The United Nations Environmental Programme estimates that annual losses from extreme weather events could reach $150 billion by the end of this decade if current trends continue; sending shockwaves through the insurance and reinsurance sectors.
Advances in climate forecasting and health early warning systems can help catalyze timely, environmentally-friendly public health interventions. If climate change continues to be associated with more volatile and severe weather, we have begun to see the profound consequences climate change can have for public health and the international economy.
|
