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Guidelines for Investors, Insurers and Policy Makers

The Science of Climate Change
James J. McCarthy Ph.D., Harvard University
Lecture Given on February 21, 2007

Lecturer Biography
Lecture Summary
Readings
Resources

Lecture Video (Streaming)
Powerpoint (PDF)

Biography

James J. McCarthy is Alexander Agassiz Professor of Biological Oceanography and from 1982 until 2002 he was the Director of Harvard University's Museum of Comparative Zoology. He holds faculty appointments in the Department of Organismic and Evolutionary Biology and the Department of Earth and Planetary Sciences, and he is the Head Tutor for degrees in Environmental Science and Public Policy. He is also the Master of Harvard's Pforzheimer House.  McCarthy received his undergraduate degree in biology from Gonzaga University, and his Ph.D. from Scripps Institution of Oceanography. 

His research interests relate to the regulation of plankton productivity in the sea, and in recent years have focused on regions that are strongly affected by seasonal and inter-annual variation in climate.  He is an author of many scientific papers, and he currently teaches courses on biological oceanography and biogeochemical cycles, marine ecosystems, and global change and human health. McCarthy has served and serves on many national and international planning committees, advisory panels, and commissions relating to oceanography, polar science, and the study of climate and global change. 

From 1986 to 1993, he chaired the international committee that establishes research priorities and oversees implementation of the International Geosphere - Biosphere Program.  He was the founding editor for the American Geophysical Union's Global Biogeochemical Cycles.  McCarthy was involved in two of the recent international assessments on climate impacts. He served as co-chair of the Intergovernmental Panel on Climate Change (IPCC), Working Group II, which had responsibilities for assessing impacts of and vulnerabilities to global climate change for the Third IPCC Assessment (2001). He was also one of the lead authors on the recently completed Arctic Climate Impact Assessment.

McCarthy is President of the American Association for the Advancement of Science, a Fellow of the American Academy of Arts and Sciences, and a Foreign Member of the Royal Swedish Academy of Sciences.

Summary

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?

Readings

IPCC, 2007: Summary for Policymakers. In: Climate Change 2007: The Physical Science Basis. Contribution of Working Group I to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change [Solomon, S., D. Qin, M. Manning, Z. Chen, M. Marquis, K.B. Averyt, M.Tignor and H.L. Miller (eds.)]. Cambridge University Press, Cambridge, United Kingdom and New York, NY, USA.

Impacts of a Warming Arctic: Arctic Climate Impact Assessment Executive Summary. Cambridge, UK: Cambridge University Press; 2004.

Resources

Hansen J. The threat to the planet. The New York Review of Books. 2006; 53(12):12-16

Climate Change 2001: The Scientific Basis. Summary for Policy-makers. A Report of Working Group I of the Intergovernmental Panel on Climate Change.

Climate Change 2001: Impacts, Adaptation, and Vulnerability. Summary for Policy-makers. A Report of Working Group II of the Intergovernmental Panel on Climate Change.

Intergovernmental Panel on Climate Change (IPCC)


Impacts of a Warming Arctic: Arctic Climate Impact Assessment. Cambridge, UK: Cambridge University Press; 2004.


The US EPA's Global Warming website