ALBERT

Notes: Abstract Trends and multi-decadal variations of weather and climate extremes have only recently received attention from the climate community. Interest has stemmed from exponentially increasing economic losses related to climate and weather extremes, and apparent increases in deaths attributed to these events, suggesting that key decision makers need a better understanding of the potential uses of climate information. The need for data on climate extremes in disaster mitigation activities such as the International Decade for Natural Disaster Reduction also has provided another motivation for focus in this area. The losses cited above raise questions as to whether extreme weather events are actually increasing in frequency, whether society as a whole is becoming more vulnerable to extreme weather events, whether public perception has been unduly influenced by enhanced media attention, or some combination. Given these questions, of particular interest here is the extent to which we can document changes in climate and weather extremes. Attribution of ongoing trends to specific climate forcings, such as anthropogenic effects or other factors related to natural climate variability are still equivocal. For some areas and variables increases in the frequency of extreme events are apparent, while in other areas there are suggestions of declines in these events. A review of this information suggests that further understanding of the cause(s) of the apparent changes in climate and weather extremes is strongly dependent upon progress in our ability to monitor and detect these multi-decadal trends. Based on these analyses we show that this will likely require increased attention in the following areas: 1) The development of more effective international data exchange for high resolution historical climate and weather records, 2) Increased emphasis on rescuing data with appropriate resolution from deteriorating manuscripts and other non-electronic media, 3) A greater emphasis on removing inhomogeneities in the instrumental record and ongoing weather monitoring programs (that provide much of our information about changes and variations of weather and climate extremes), 4) More effective use of space-based measurements and reanalysis products derived from models, 5) More robust monitoring of local extreme weather events such as tornadoes, hail, lightning, and wind, and 6) More effective means to integrate and communicate information about what we know and do not know about changes in climate extremes. Progress in each of these areas is reviewed in context with outstanding remaining challenges, and the benefits that can be expected if we meet these requirements.