Insurance is a mechanism for spreading risk over time, across large geographical areas, and among industries and individuals. While private insurers assume some financial risk when they write policies, they employ various strategies to manage risk so that they earn profits, limit potential financial exposure, and build capital needed to pay claims. For example, insurers charge premiums for coverage and establish underwriting standards, such as refusing to insure customers who pose unacceptable levels of risk or limiting coverage in particular geographic areas. Insurance companies may also purchase reinsurance to cover specific portions of their financial risk. Reinsurers use strategies similar to primary insurers to limit their risks. Under certain circumstances, the private sector may determine that a risk is uninsurable. For example, homeowner policies typically do not cover flood damage because private insurers are unwilling to accept the risk of potentially catastrophic losses associated with flooding. In other instances, the private sector may be willing to insure a risk, but at rates that are not affordable to many property owners. Without insurance, affected property owners must rely on their own resources or seek out disaster assistance from local, state, and federal sources. In situations where the private sector will not insure a particular type of risk, the public sector may create markets to ensure the availability of insurance. The federal government operates two such programs—the NFIP and the FCIC. NFIP provides insurance for flood damage to homeowners and commercial property owners in more than 20,000 communities. Homeowners with mortgages from federally regulated lenders on property in communities identified as being in high flood risk areas are required to purchase flood insurance on their dwellings. Optional, lower cost flood insurance is also available under the NFIP for properties in areas of lower flood risk. NFIP offers coverage for both the property and its contents, which may be purchased separately. FCIC insures agricultural commodities on a crop-by-crop and county-by-county basis based on farmer demand and the level of risk associated with the crop in a given region. Major crops, such as grains, are covered in almost every county where they are grown, while specialty crops such as fruit are covered only in some areas. Participating farmers can purchase different types of crop insurance and at different levels. Assessments by leading scientific bodies suggest that climate change could significantly alter the frequency or severity of weather-related events, such as drought and hurricanes. Leading scientific bodies report that the Earth warmed during the twentieth century— 1.3 degrees Fahrenheit (0.74 degrees Celsius) from 1906 to 2005 according to a recent IPCC report—and is projected to continue to warm for the foreseeable future. While temperatures have varied throughout history, triggered by natural factors such as volcanic eruptions or changes in the earth’s orbit, the key scientific assessments we reviewed have generally concluded that the observed increase in temperature in the past 100 years cannot be explained by natural variability alone. In recent years, major scientific bodies such as the IPCC, NAS, and the United Kingdom’s Royal Academy have concluded that human activities are significantly increasing the concentrations of greenhouse gases and, in turn, global temperatures. Assuming continued growth in atmospheric concentration of greenhouse gases, the latest assessment of computer climate models projects that average global temperatures will warm by an additional 3.2 to 7.2 degrees Fahrenheit (1.8 to 4.0 degrees Celsius) during the next century. Based on model projections and expert judgment, the IPCC reported that future increases in the earth’s temperature are likely to increase the frequency and severity of many damaging extreme weather-related events (summarized in table 1). The IPCC recently published summaries of two of the three components of its Fourth Assessment Report. The first, in which IPCC summarized the state of the physical science, reports higher confidence in projected patterns of warming and other regional-scale features, including changes in wind patterns, precipitation, and some aspects of extreme events such as drought, heavy precipitation events, and hurricanes. The second, in which IPCC addresses climate impacts and vulnerabilities, reported that the potential societal impacts from changes in temperature and extreme events vary widely across sector and region. For example, although the IPCC projects moderate climate change may increase yields for some rain-fed crops, crops that are near their warm temperature limit or depend on highly-used water resources face many challenges. Additionally, local crop production in any affected area may be negatively impacted by projected increases in the frequency of droughts or floods. Furthermore, the IPCC stated that the economic and social costs of extreme weather events will increase as these events become more intense and/or more frequent. Rapidly-growing coastal areas are particularly vulnerable, and the IPCC notes that readiness for increased exposure in these areas is low. These reports have not been publicly released in their entirety, but are expected sometime after May 2007. In addition to the IPCC’s work, CCSP is assessing potential changes in the frequency or intensity of weather-related events specific to North America in a report scheduled for release in 2008. According to a National Oceanic and Atmospheric Administration official and agency documents, the report will focus on weather extremes that have a significant societal impact, such as extreme cold or heat spells, tropical and extra-tropical storms, and droughts. Importantly, officials have said the report will provide an assessment of the observed changes in weather and climate extremes, as well as future projections. Based on an examination of loss data from several different sources, we found that insurers incurred about $321.2 billion in weather-related losses from 1980 through 2005. In particular, as illustrated in Figure 1, our analysis found that weather-related losses accounted for 88 percent of all property losses paid by insurers during this period. All other property losses, including those associated with earthquakes and terrorist events, accounted for the remainder. Weather-related losses varied significantly from year to year, ranging from just over $2 billion in 1987 to more than $75 billion in 2005. Private insurers paid $243.5 billion—over 75 percent of the total weather- related losses we reviewed. The two major federal insurance programs— NFIP and FCIC—paid the remaining $77.7 billion of the $321.2 billion in weather-related loss payments we reviewed. NFIP paid about $34.1 billion, or about 11 percent of the total weather-related loss payments we reviewed during this period. As illustrated in Figure 2, claims averaged about $1.3 billion per year, but ranged from $75.7 million in 1988 to $16.7 billion in 2005. Since 1980, FCIC claims totaled $43.6 billion, or about 14 percent of all weather-related claims during this period. As illustrated in Figure 3, FCIC losses averaged about $1.7 billion per year, ranging from $531.8 million in 1987 to $4.2 billion in 2002. The largest insured losses in the data we reviewed were associated with catastrophic weather events. Notably, crop insurers and other property insurers both face catastrophic weather-related risks, although the nature of the events for each is very different. In the case of crop insurance, drought accounted for more than 40 percent of weather-related loss payments from 1980 to 2005, and the years with the largest losses were associated with drought. Taken together, though, hurricanes were the most costly event in the data we reviewed. Although the United States experienced an average of only two hurricanes per year from 1980 through 2005, weather-related claims attributable to hurricanes totaled more than 45 percent of all weather-related losses—more than $146 billion. Moreover, as illustrated in Table 2, these losses appear to have increased during the past three decades. Several recent studies have commented on the apparent increases in hurricane losses during this time period, and weather-related disaster losses generally, with markedly different interpretations. Some argue that loss trends are largely explained by changes in societal and economic factors, such as population density, cost of building materials, and the structure of insurance policies. Others argue that increases in losses have been driven by changes in climate. To address the issue, Munich Re—one of the world’s largest reinsurance companies—and the University of Colorado’s Center for Science and Technology Policy Research jointly convened a workshop in Germany in May 2006 to assess factors leading to increasing weather-related losses. The workshop brought together a diverse group of international experts in the fields of climatology and disaster research. Workshop participants agreed that long-term records of disaster losses indicate that societal change and economic development are the principal factors explaining weather-related losses. However, participants also agreed that changing patterns of extreme events are drivers for recent increases in losses, and that additional increases in losses are likely, given IPCC’s projections. The close relationship between the value of the resource exposed to weather-related losses and the amount of damage incurred may have ominous implications for a nation experiencing rapid growth in some of its most disaster-prone areas. AIR Worldwide, a leading catastrophe modeling firm, recently reported that insured losses should be expected to double roughly every 10 years because of increases in construction costs, increases in the number of structures, and changes in their characteristics. AIR’s research estimates that, because of exposure growth, probable maximum catastrophe loss—an estimate of the largest possible loss that may occur, given the worst combination of circumstances—grew in constant 2005 dollars from $60 billion in 1995 to $110 billion in 2005, and it will likely grow to over $200 billion during the next 10 years. Major private and federal insurers are responding differently to the prospect of increasing weather-related losses associated with climate change. Many large private insurers are incorporating both near and longer-term elements of climatic change into their risk management practices. On the other hand, for a variety of reasons, the federal insurance programs have done little to develop the kind of information needed to understand the programs’ long-term exposure to climate change.