Climate Change and Extreme Events

Q2. Your testimony on page 4 states that, "More precipitation is likely to occur in 'extreme' downpours, where large amounts of rain fall in a short period. Some areas will be threatened by increased flooding, while others will suffer through an increased incidence of drought, as continental interiors become warmer and drier." However, the 1995 IPCC report, The Science of Climate Change, concludes on page 336: “Except maybe for precipitation, there is little agreement between models on changes in extreme events [emphasis added]." And even concerning precipitation, it concludes: “Several models suggest an increase in the precipitation intensity, suggesting a possibility for more extreme rainfall events [emphasis added].”

A2.

Do you agree with these IPCC conclusions?

I accept the 1995 IPCC findings as a typically cautious summary of worldwide scientific understanding based on scientific findings through early 1995. Because of the importance of potential changes in extreme events, research in this area has intensified. The increased confidence expressed in my testimony reflects the developing understanding and the emerging scientific findings.

Analyses by Tom Karl of NOAA's National Climatic Data Center show that the precipitation increases we are seeing over the last century are coming primarily as high intensity, extreme events. Total rainfall has increased in the U.S. by 5-10% in the last century, and it is the rainfall events of more than 2 inches per day that have increased the most.

It is well accepted that the increased energy associated with global warming will lead to more evaporation and more water vapor in the atmosphere, which will mean in turn more energy and water vapor to be converted into intense rainstorms as convection occurs. Just as summer and warm region (e.g., El Niño affected) rainstorms produce much more rainfall in shorter times than do winter and cold region storms, there is a very strong foundation for saying, as I did, that "More precipitation is likely to occur in 'extreme' downpours."

Stronger downpours will also lead to increased threats of flooding. And warmer temperatures will lead to increased evaporation (so dryness and then drought) in regions where precipitation events are now infrequent and may in the future be missed by the intensified storms. Our natural hazards studies suggest we should be very concerned about the trend toward an increased frequency and intensification

Q3.

A3.

With respect to your statement on page 4 that “Some areas will be threatened by increased flooding, while others will suffer through an increased incidence of drought, as continental interiors become warmer and drier," isn't it also likely to be true that some areas will have decreased flooding and decreased incidence of drought”?

Yes. Some areas will experience decreased flooding and others will have a decreased incidence of drought. Overall, however, precipitation is projected to increase worldwide, and intensity of precipitation is expected to increase with warmer weather, so when it does rain, flooding will be more likely. Further, already drought-prone areas are likely to become increasingly arid because of additional warming.

Documentation of 1997 Temperature Statistics

Q4. Your testimony on page 4 also states that “new results from the National Oceanic and Atmospheric Administration (NOAA) show that 1995 has been surpassed by 1997, and that nine of the last eleven years are among the warmest ever recorded (Figure 1). 1997 also shows up as the warmest year in data records maintained by the United Kingdom Meteorological Office and the NASA Goddard Institute of Space Studies, meaning that the three most comprehensive and accurate long-term surface data records all indicate continued warming of our planet."

Q4.1 Please provide a copy of NOAA report and accompanying data/statistics referred to in your statement above.

A4.1 Attached are a NOAA graph of the annual global temperature index and a figure showing global temperature anomalies for 1997 and a press release from NOAA discussing the results of an analysis by a team led by Dr. Tom Further details can be found on the NOAA/NCDC home page at

Karl.

http://www.ncdc.noaa.gov/ol/climate/research/1997/climate97.html.

1997 WARMEST YEAR OF CENTURY, NOAA REPORTS

1997 was the warmest year of this century, based on land and ocean surface temperature data, reports a team of scientists from the National Oceanic and Atmospheric Administration's National Climatic Data Center in Asheville, N. C.

Led by the center's Senior Scientist Tom Karl, the team analyzed temperatures from around the globe during the years 1900 to 1997 and back to 1880 for land areas. For 1997, land and ocean temperatures averaged three-quarters of a degree Fahrenheit above normal. (Normal is defined by the mean temperature, 61.7 degrees F, for the 30-years 1961-90.) The 1997 figure exceeds the previous record warm year, 1990, by 0.15 degrees Fahrenheit.

The record-breaking warm conditions of 1997 continues the pattern of very warm global temperatures. Nine of the past eleven years have been the warmest on record.

"Land temperatures did not break the previous record set in 1990, but 1997 was one of the five warmest years since 1880," said Karl. Including 1997, the top ten warmest years over the land have all occurred since 1981, and the warmest five years all since 1990. Land temperatures for 1997 averaged three-quarters of a degree above normal, falling short of the 1990 record by one-quarter of a degree.

Ocean temperatures during 1997 also averaged three-quarters of a degree above normal, which makes it the warmest year on record, exceeding the previous record warm years of 1987 and 1995 by 0.3 of a degree Fahrenheit.

With the new data factored in, global temperature warming trends now exceed 1.0 degree Fahrenheit per 100 years, with land temperatures warming at a somewhat faster rate. "It is likely that the sustained trend toward increasingly warmer global temperatures is related to anthropogenic increases in greenhouse gases," Karl said.

Annual Global Temperature Index

National Climatic Data Center / NESDIS / NOAA

1997: +0.42 °C (+0.76 °F)

The global average temperature of 62.45 degrees Fahrenheit for 1997 was the warmest on record, surpassing the previous record set in 1995 by 0.15 degrees Fahrenheit. The chart reflects variations from the 30-year average (1961