Response. This question had been addressed separately by another NRC committee, with a report issued in 1999. The chairman of that committee was a member of the Climate Change Science committee.

Question 8. Who wrote the IPCC summary for policymakers?

Response. I was not part of the IPCC process, and know only anecdotally that the listed authors appear to have worked much like the Climate Change Science committee, except that their interactions were stretched out over months and years.

Question 9. Which uncertainties in the underlying IPCC Working Group reports were also reflected in the NRC (June 2001) report?

Response. I think that the same general sets of uncertainties were involved in both, but the IPCC Working Group reports cover more than 2500 pages as published and obviously can discuss uncertainties on a more micro scale.

Question 10. In your written testimony you said that increased greenhouse gas concentrations are "often because of the activities of mankind." Yet in you oral comments you said they were "mostly caused by the activities of man." There is a significant difference between "often" and "mostly." Many people attach much meaning to the individual words of the IPCC Reports and other Climate Reports. Could you explain what you meant in your two different testimonies?

Response. The two terms "often” and “mostly" are complementary, and both are different from "always" because some of the emission sources for some of the greenhouse gases are of natural origin. For those molecules with both natural sources and releases by the activities of mankind, the source is no longer distinguishable when the molecule is in the atmosphere, but the increase in the atmospheric concentration is then usually caused by the addition of the anthropogenic source rather than by a change in the non-human processes. There are many different greenhouse gases and many different ways in which mankind causes them to be put into the atmosphere. Thirty years ago discussions about global warming might be alternately described as "the carbon dioxide problem". Then, in the 1970's a succession of measurements showed increasing concentrations in the atmosphere of methane, nitrous oxide, and the chlorofluorocarbons (CFC-11, CFC-12 and CFC-113, and the alternate description became "the greenhouse gas problem". The only important greenhouse gas not listed as such is water vapor, for which the atmospheric concentration is controlled by the temperature of the ocean through evaporation. With further research, the greenhouse gas list was expanded to include sulfur hexafluoride, the perfluorocarbons (such as CF4 and C2F6) and the hydrofluorocarbons (such as CH2FCF3, now the common refrigerant 134A in automobile air conditioners.). Volume One of the IPCC 2001 report lists 64 greenhouse gases. Carbon dioxide, methane and nitrous oxide have been components of the atmosphere for hundreds of thousands of years, and have always had natural sources. However, for each of three molecules, there now exist substantial sources of emissions under the control of mankind, and most of the increase, in their concentrations arises from these widely varying activities of mankind: burning of coal, gas and oil for carbon dioxide, release from rice paddies and cattle for methane, microbial action on fertilizers for nitrous oxide. For the other 60+ molecules, no natural sources are known and their presence in the atmosphere results from chemical synthesis by man, and then release to the atmosphere unchanged. These compounds are used in a very wide variety of human activities, with the common characteristic that release to the atmosphere unchanged is the usual occurrence. When it comes to evaluation of the cumulative greenhouse effect of all of these gases, then carbon dioxide is the most important, accounting for roughly half of the total, with methane and nitrous oxide having significant roles. The incremental changes in the total greenhouse gas effect are mostly the product of some activity of mankind.

STATEMENT OF DR. ROGER A. PIELKE, JR., UNIVERSITY OF COLORADO, BOULDER, CO

I thank the chairman and the committee for the opportunity to offer testimony this morning on the economic and environmental risks associated with increasing greenhouse gas emissions.

My name is Roger Pielke, Jr. and I am an Associate Professor of Environmental Studies at the University of Colorado where I also direct the CIRES Center for Science and Technology Policy Research. My research focuses on the connections of science and decisionmaking. A short biography can be found at the end of my written testimony.

In my oral testimony I'd like to highlight six "take home points," which are developed in greater detail in my written testimony and in the various peer-reviewed scientific papers cited therein.

TAKE HOME POINTS

• Weather and climate have growing impacts on economies and people around the world. 1

• The primary cause for the growth in impacts is the increasing vulnerability of human and environmental systems to climate variability and change, not changes in climate per se.2

• To address increasing vulnerability, and the growing impacts that result, requires a broader conception of "climate policy" than now dominates debate.3

We must begin to consider adaptation to climate to be as important as matters of energy policy in discussion of response options. Present discussion all but completely neglects adaptation.4

• Increased attention to adaptation would not mean that we should ignore energy policies, but instead is a recognition that changes in energy policy are insufficient to address the primary reasons underlying trends in the societal impacts of weather and climate.5

• The nation's investments in research could be more efficiently focused on producing usable information for decisionmakers seeking to reduce vulnerabilities to climate. Specifically, the present research agenda is improperly focused on prediction of the distant climate future.6

The remainder of this document develops these points through a case study focused on tropical cyclones. Considerably more detail can be found in the set of peerreviewed articles cited in support of the arguments presented here.

Policy debate and advocacy on the issue of climate change frequently focus on the potential future impacts of climate on society, usually expressed as economic damage or other human outcomes. Today I would like to emphasize that societal impacts of climate are a joint result of climate phenomena (e.g., hurricanes, floods, and other extremes) and societal vulnerability to those phenomena. The paper concludes that policies focused on reducing societal vulnerability to the impacts of climate have important and under-appreciated dimensions that are independent of energy policy.

In the climate change debate, people often point to possible increases in extreme weather events (e.g., hurricanes, floods, and winter storms) as a potentially serious consequence of climate change for humans around the world. For instance, the January 22, 1998 issue of Newsweek carried the following headline: "THE HOT ZONE: Blizzards, Floods, and Hurricanes, Blame Global Warming." In this testimony I use the case of hurricanes to illustrate the interrelated climate-society dimensions of climate impacts. Research indicates that societal vulnerability is the single most important factor in the growing damage related to extreme events. An implication of this research for policy is that decisionmaking at local levels (such as related to land use, insurance, building codes, warning and evacuation, etc.) can have a profound effect on the magnitude and significance of future damage.?

Figure 1 shows economic damage (adjusted for inflation) related to hurricane landfalls in the United States, 1900-1998.8 Because damage is growing in both frequency and intensity, one possible interpretation of this figure is that hurricanes have become more frequent and possibly stronger in recent decades. However, while hurricane frequencies have varied a great deal over the past 100+ years, they have not increased in recent decades (Figure 2, provided courtesy of C. Landsea, NOAA).9 To the contrary, although damage increased during the 1970's and 1980's, hurricane activity was considerably lower than in previous decades.

To explain the increase in damage it is necessary to consider factors other than climate. In particular, society has changed enormously during the period covered by Figure 2. Figures 3a and b show this dramatically. Figure 4a shows a stretch of Miami Beach in 1926. Figure 3b shows another perspective of Miami Beach from recent years. The reason for increasing damages is apparent from the changes easily observable in these figures: today there is more potential for economic damage than in the past due to population growth and increased wealth (e.g., personal property).

Figure 4b shows the increase in population along the Gulf and Atlantic coasts for 168 coastal counties from Texas through Maine (Figure 4a). In 1990, the population of Miami and Ft. Lauderdale (2 counties) exceeded the combined population of 107 counties from Texas to Virginia. 10 Clearly, societal changes such as coastal population growth have had a profound effect on the frequency and magnitude of impacts from weather events such as hurricanes. 11

One way to present a more accurate perspective on trends in hurricane-related impacts is to consider how past storms would affect present society. A 1998 paper presented a methodology for "normalizing" past hurricane damage to present day values (using wealth, population and inflation). Figure 5 shows the historical losses of Figure 1 normalized to 2000 values. 12

The normalized record shows that the impacts of Hurricane Andrew, at close to $40 billion (2000 values), would have been far surpassed by the Great Miami Hurricane of 1926, which would cause an estimated $90 billion damage had it occurred in 2000. We can have confidence that the normalized loss record accounts for societal changes because the adjusted data contains climatological information, such as the signal of El Niño and La Niña. 13

The normalization methodology provides an opportunity to perform a sensitivity analysis of the relative contributions of climate changes and societal changes, as projected by the Intergovernmental Panel on Climate Change (IPCC), to future topical cyclone damages. Figure 6 shows the results of this analysis. 14 The three blue bars show three different calculations (named for their respective authors) used by IPCC in its Second Assessment Report for the increase in tropical cyclone-related damage in 2050 (relative to 2000) resulting from changes in the climate, independent of any changes in society. The four green bars show the sensitivity of tropical cyclone-related damage in 2050 (relative to 2000) resulting from changes in society based on four different IPCC population and wealth scenarios used in its Third Assessment Report. These changes are independent of any changes in climate.

Figure 6 illustrates dramatically the profound sensitivity of future climate impacts to societal change, even in the context of climate changes projected by the IPCC. The relative sensitivity of societal change to climate change ranges from 22 to 1 (i.e., smallest societal sensitivity and largest climate sensitivity) to 60 to 1 (i.e., largest societal sensitivity and smallest climate sensitivity). This indicates that insofar as tropical cyclones are concerned, steps taken to modulate the future climate (e.g., via greenhouse gas emissions or other energy policies) would only address a very small portion of the increasing damages caused by tropical cyclones. Similar results have been found for tropical cyclone impacts in developing countries, 15 flooding,16 other extremes,17 and water resources. 18