Ethon had joined Eli in his new retirement village and they were sitting outside enjoying their cool beverages and reading the US EPA responses to challenges to its Endangerment Finding for increasing CO2 concentrations. Eli was reminiscing how he and Nils Simon had shown that Ethons source of little liver treats had made a living by omitting a whole lot of important things from his discussion of hurricane damage. As old buddies are often fond of doing, they chortled when reading Comment 7-5 and the Response
Comment (7-5):Stay tuned to more adventures of your EPA.
A commenter (3136.1) states that the TSD does not mention that there have been no observed increases in trends of flood-related damages while global temperatures have increased over the past century. The commenter cites Downton et al. (2005), and argues that this paper indicates that there is no detectable increase in flood losses in the face of rising temperatures when population growth and wealth are accounted for. The commenter argues that given this evidence, climate change effects on flood-related damages should not be used as a basis for determining endangerment.
We find that the commenter has misinterpreted the findings of the Downton et al. (2005) paper. This study “presents results of a reanalysis of NWS flood damage estimates from 1926 to 2000. It describes National Weather Service methods of collecting flood damage estimates, explains some of the limitations and problems in the data, and recommends appropriate methods of interpretation and use.” After careful review, we do not find evidence within this study which suggests that increases in intense precipitation have resulted in no increases in flooding, as suggested by the commenter. In fact, this paper does not directly analyze the relation between precipitation intensity and flood frequency and/or intensity. Rather, Downton et al. (2005) [Downton, W.M., J.Z.B. Miller, and R.A. Pielke Jr. (2005). Reanalysis of U.S. National Weather Service Flood Loss Database. Natural Hazards Review 6:13-22] analyzes trends in flood damage data and identifies sources of error in the damage estimates. At a national level, the study finds that “Total damage and per capita damage have increased significantly since 1934 (statistically significant at a 95% confidence level). On the other hand, damage per unit wealth has declined slightly (although the trend is significant only at an 85% confidence level).” However, no correlation or connection is analyzed with changing precipitation intensity or amount.
Regarding weather-related damages such as flooding, we note the conclusions of the U.S. Climate Change Science Program (CCSP) (2008i) which state that “Numerous studies indicate that both the climate and the socioeconomic vulnerability to weather and climate extremes are changing (Brooks and Doswell, 2001; Pielke et al., 2008; Downton et al., 2005), although these factors’ relative contributions to observed increases in disaster costs are subject to debate. For example, it is not easy to quantify the extent to which increases in coastal building damage is due to increasing wealth and population growth in vulnerable locations versus an increase in storm intensity. Some authors (e.g., Pielke et al., 2008) divide damage costs by a wealth factor in order to ‘normalize’ the damage costs. However, other factors such as changes in building codes, emergency response, warning systems, etc. also need to be taken into account.
At this time, there is no universally accepted approach to normalizing damage costs (Guha-Sapir et al., 2004). Though the causes of the current damage increases are difficult to quantitatively assess, it is clear that any change in extremes will have a significant impact.” These CCSP conclusions are consistent with Downton et al. (2005) which states that “Although flood damage fluctuates greatly from year to year, estimates indicate an increasing trend over the past century (Pielke and Downton 2000). To understand increasing damage and assess implications for policy, decision makers need to recognize the influences of climate, population growth, land use, and policy on trends in damage. An increase in flood damage due to changing climate would probably require different policy actions than would damage increases due to implementation of flood policies.”
We also note that monetized flood-related damages, as studied by Downton et al. (2005), are only one type of flood-related effect on health and welfare. Other important damages discussed in the TSD include increased morbidity and mortality, adverse impacts to wildlife and habitat loss, impaired water quality, and other effects that are generally not included in flood damage estimates. To provide additional context regarding the future impacts of climate change on flooding, several studies reviewed and cited by Kundzewicz et al. (2007) indicate that increases intense precipitation will result in adverse impacts:
* Choi and Fisher (2003) estimated the expected change in flood damages for selected U.S. regions under two climate-change scenarios in which mean annual precipitation increased by 13.5% and 21.5%, respectively, with the standard deviation of annual precipitation either remaining unchanged or increasing proportionally. They used a structural econometric (regression) model based on time series of flood damage and population, wealth indicator, and annual precipitation as predictors. They found that the mean and standard deviation of flood damage are projected to increase by more than 140% if the mean and standard deviation of annual precipitation increase by 13.5%. The estimates suggest that flood losses are related to exposure because the explanatory power of population and wealth is 82%, while adding precipitation increases the explanatory power to 89%.
*Another study examined the potential flood damage impacts of changes in extreme precipitation events using the Canadian Climate Centre model and the IS92a emissions scenario for the metropolitan Boston area in the northeastern United States (Kirshen et al., 2005). They found that, without adaptation investments, both the number of properties damaged by floods and the overall cost of flood damage would double by 2100 relative to what might be expected with no climate change, and that flood-related transportation delays would become an increasingly significant nuisance over the course of the century.
After review of the studies submitted during the public comment process, we find that literature presented in the TSD is an accurate and reasonable summary of current scientific understanding. See the Findings, Section IV.B, “The Air Pollution Is Reasonably Anticipated to Endanger Both Public Health and Welfare,” for our response to comments on how the Administrator weighed the scientific evidence underlying her endangerment determination.