You’ve utilized more of a political global warming model than a purely scientific one. How does your research vary from a purely scientific model and what effect does this have on your conclusions in comparison to most research on global warming?

This question implicitly defines physical science (in this case climatology) as “scientific” and social science (in this case economics) as not (purely) “scientific.” Both the studies my colleagues and I did and the (bio)physical climatology studies reported by the Intergovernmental Panel on Climate Change (IPCC) make enormously simplified assumptions about complex systems (including biological components in both cases) and then do rigorous quantitative analysis to come up with projected probability distributions for outcomes. Both of these are different from analyses of simpler physical systems based on basic physics principles and from the qualitative studies often done by political scientists. (Political scientists also do quantitative studies, but less commonly use them for projections of future behavior.) The distinction here is the relative emphasis on human behavior as a component of the systems under study. Humans have a role in both econometrics and physical climatology. They are carbon emitters in econometric studies, and are part of the biological system that determines rates of carbon fixation (conversion of carbon dioxide into organic compounds by plant life), such as through agriculture and forest management, when studying the physical climatology response to assumed carbon emissions scenarios.

The contributors to the IPCC reports included a large complement of physical scientists (though economists are also included) and seem to be more comfortable with quantifying uncertainty in the climate response to carbon emissions than in quantifying the uncertainty in the emissions themselves. It is not that our conclusions were in any way inconsistent with the content of the IPCC report, but rather we were focusing primarily on quantifying the uncertainties in the carbon emissions and thus to a large extent asking (and answering) a different question than focused on in the fourth (and most recent) IPCC report. There is discussion within the IPCC on what to do about this, which may or may not be evident in the fifth IPCC assessment (if there is a fifth assessment).

According to your models, the worst-case scenarios (average temperature increases of 7-9 degrees Farenheit) proposed by the Intergovernmental Panel on Climate Change (IPCC) are unlikely. However, you believe global warming is still very likely to be serious. Considering current trends and conditions, what kind of changes can we reasonably expect on Earth over the next 100 years?

Based on the IPCC Forth Assessment Report, for the carbon emissions scenarios identified as most likely within the context of the assumptions used in our study, the following effects are likely
a) Longer temperate growing seasons (e.g. the U.S. and Europe)
b) More droughts in parts of Africa and South America
c) Probably more tropical storm damage
d) Unprecedented rapid ecological change
e) Ice cap melting and major sea level rise, gradually over the current millennium

Ice cap melting may be avoidable by a global scale effort, specifically biological carbon sequestration (capturing carbon emissions) after this century, even if the emissions projected for this century come to pass. I have not looked for literature on this.

You suggest that temperature change will affect us differently than other parts of the world. Where do you see global warming having the greatest impact, and what economic impacts do you see as likely over the next century in those regions?

In general, climate change is most serious for people and countries with the lowest per capita incomes. There is particular concern about deleterious affects on agriculture in marginal rainfall areas in Africa and tropical storm impact on developing countries like Bangladesh. Populations for species other than humans are also likely to be drastically affected.

Global warming is generally considered to be caused by the trapping of greenhouse gases like carbon dioxide in our atmosphere. What recommendations would you make to governments around the world to reduce carbon emissions and decrease carbon levels in the atmosphere?

From the point of view of effects on human populations, the most cost effective approach is probably to pay serious attention to implementing the goals of the Millennium Challenge, which aims to break the poverty cycle for over a billion people currently living at subsistence level. Proponents think that properly applied (and this is the hard part even if the money can be raised), an expenditure of about $1,000 per capita spread over 10 years could be sufficient. (At this level, the total for a billion people would be less than the estimated cost to the United States alone of the current war in Iraq.) A more orderly process for dealing with cross-border migration would also help, since some areas of the world will be more productive and others less in this century as a result of climate change, if it proceeds according to results from the assumptions we have made.

There is a lot of potential for increased efficiency of energy and carbon use, particularly in the United States and Canada. Taking a long term view, this is especially the case for new construction, particularly residential but commercial construction also.. Getting this to happen is not easy, as it requires coordination between national and regional governments and the private sector, particularly at the local planning level. Both the amount of energy and carbon used in the transportation sector will be reduced substantially if import tariffs are used to keep the cost of imported oil up at a high and predictable level. (Other approaches to limiting carbon emissions from transportation are likely to be less effective.) Reducing the mileage that people drive in the United States is also potentially important. One potentially important but politically difficult response is to provide enough K-14 education funding through sources other than local property and sales taxes to allow high quality education to be available near where people work, in order to help reduce the incentive to spend lots of time and energy commuting.

For developed countries to continue to substantially decrease their energy and carbon use is necessary but not sufficient for stabilizing atmospheric carbon concentrations in the 21st century. Providing developing countries like China, India, and Indonesia adequate incentives to limit their carbon emissions without affecting their growth could require the direct or indirect transfer of another trillion dollars or more from the industrialized countries that caused much of the problem in the first place. Even if such transfers could be negotiated, they would only provide a net benefit to the most severely affected human populations if they add to rather than displace the more urgent response to the Millennium Challenge. Doing it in a way that is effective in reducing carbon emissions by developing countries would not be easy, even if the will to do so evolved in the developing countries. The same is true for migration and the Millennium Challenge. The hard part is not making recommendations, but figuring out how to get some of them implemented in practice.

Posted by Matt VanderZalm on September 25, 2007 12:16 PM | Permalink