WMO-recommended 30-yr normals are no longer generally useful for the design, planning, and decisionmaking purposes for which they were intended. They not only have little relevance to the future climate, but are often unrepresentative of the current climate. The reason for this is rapid global climate change over the last 30 yr that is likely to continue into the future. It is demonstrated that simple empirical alternatives already are available that not only produce reasonably accurate normals for the current climate but also often justify their extrapolation to several years into the future. This result is tied to the condition that recent trends in the climate are approximately linear or have a substantial linear component. This condition is generally satisfied for the U.S. climate-division data. One alternative [the optimal climate normal (OCN)] is multiyear averages that are not fixed at 30 yr like WMO normals are but rather are adapted climate record by climate record based on easily estimated characteristics of the records. The OCN works well except with very strong trends or longer extrapolations with more moderate trends. In these cases least squares linear trend fits to the period since the mid-1970s are viable alternatives. An even better alternative is the use of “hinge fit” normals, based on modeling the time dependence of large-scale climate change. Here, longer records can be exploited to stabilize estimates of modern trends. Related issues are the need to avoid arbitrary trend fitting and to account for trends in studies of ENSO impacts. Given these results, the authors recommend that (a) the WMO and national climate services address new policies for changing climate normals using the results here as a starting point and (b) NOAA initiate a program for improved estimates and forecasts of official U.S. normals, including operational implementation of a simple hybrid system that combines the advantages of both the OCN and the hinge fit.

Software Testing, Verification and ReliabilityVolume 1, Issue 2 p. 59-60 Book ReviewFree Access Software design for real-time systems; J.E. Cooling 506 pages, ISBN 0-412-34180-8, £39.95; Published by Chapman and Hall Richard Tinker, Richard Tinker Software Technology Division, British Telecom Research Labs, Martlesham Heath, Ipswich IP5 7RE, UKSearch for more papers by this author Richard Tinker, Richard Tinker Software Technology Division, British Telecom Research Labs, Martlesham Heath, Ipswich IP5 7RE, UKSearch for more papers by this author First published: July/September 1991 https://doi.org/10.1002/stvr.4370010207AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat No abstract is available for this article. Volume1, Issue2July/September 1991Pages 59-60 RelatedInformation