G. Farmer

Marine and Land Temperature Data Sets: A Comparison and a Look at Recent Trends

Abstract Comparisons are made among the various data sets of marine and land temperatures. Emphasis in the analyses is placed on the first intercomparison of the two marine data sets, the United Kingdom Meteorological Office (UKMO) and the Comprehensive Ocean-Atmosphere Data Set (COADS). The results of the analyses show that the two data sets are not the same, as some authors have assumed. Important differences are noted prior to 1940, with hemispheric averages differing by up to 0.2°C for some decades during the nineteenth century. Patterns of regional temperature change over the two major periods of global warming this century, 1920–39 and 1967–86, are shown.

Use of simple daily atmospheric circulation types for the interpretation of precipitation composition at a site (Eskdalemuir) in Scotland, 1978-1984.

Abstract A simple daily weather type of classification for the British Isles (Lamb, 1972, Geophys. Mem. 16 ) may be used as a convenient method to categorize precipitation composition (excess SO 2− 4 , NO − 3 , NH − 3 , NH + 4 , H + ) at a site in southern Scotland. Precipitation associated with four weather types in particular (Westerly: W, Cyclonic: C, Southerly: S, Southwesterly: SW), has a strong influence on the annual mean precipitation-weighted composition. The single most important influence is the ‘dilution’ effect of precipitation associated with W-types. Trends in composition over the period 1978–1984 appear to be strongly related to the annual amounts of C-type and, especially, W-type precipitation. These links may confound the relationships between emissions and deposition over a restricted region. The pronounced annual cycle in precipitation composition at the station may also be explained, in large part, by the annual meteorological cycle which can, in turn, be characterized by the weather types. The significance of these findings is that there are known, and large, change in the relative annual frequencies of the major weather types on time-scales of decades. This indicates a possible contribution to non-linearity between emissions and depositions on the longer time-scale.

Rainfall variability in tropical Africa: Some implications for policy☆

Abstract Rain is the basic ingredient for the existence of Africa and its people. This article introduces the ‘baseline’ rainfall climatology of Africa and looks at examples of fluctuations in the last 50 years. The author then puts forward some suggestions on the implications of such variability for planning and policy making.

Surface pressure pattern indicators of mean monthly pollutant concentrations in southern Scandinavian precipitation: A test using case studies of months with high and low concentrations of non-marine sulphate and nitrate

Abstract Regional averages of monthly precipitation-weighted non-marine (nm) SO 4 2− concentrations have been used to identify months of relatively high, and relatively low, concentrations in southern Scandinavia. Composite monthly maps of actual sea-level pressure, and sea-level pressure anomalies from the long-term mean, were compiled to identify circulation patterns which are associated with high and low nm SO 4 2− concentrations. The composite patterns indicate relatively enhanced flow with a southerly component for months with high concentrations, and relatively enhanced flow with a westerly component for months with low concentrations. Physical reality was tested by examining the back-trajectories associated with daily precipitation at four locations in southern Norway and southern Sweden, for 1 month with high concentrations of nm SO 4 2− and NO 3 − , and for 1 month with low concentrations. The analysis allowed an examination of the relationships between daily precipitation composition at each site and on assessment of the synchroneity of ‘episodes’ over space. In spite of the considerably different precipitation composition regimes at each station on the synoptic time-scale, the clusters of back-trajectories and the synoptic meteorology confirm that the mean monthly circulation patterns do provide physically-sensible information on the chemical character of precipitation events. This is a useful confirmation, since a simple climatological approach to wet acidic deposition may make a contribution to reconstruction of past wet pollutant deposition climates, or may be developed as one way of estimating future wet deposition regimes from the projections of climate models.

Climate Reconstruction Using Historical Sources

Winter severity indices for Europe are compared and evaluated. New values are presented for the period 1220–1420 A.D. Overall, the data show long time scale cooling from c. 1200 to c. 1340, warming to c. 1510 and then cooling into the main Little Ice Age cold period of the 17th century.

Climatic Variation in the North Sea Region

Climatic change has become of increasing concern in recent years. This is partially due to greater stress on the world’s limited resources but it is also a reflection of increased awareness of environmental matters and, in particular, the realization that society may be about to bring upon itself a major climatic change. This paper presents a brief summary of the data available for studies of past and present climatic variation in the North Sea region. The possibility of long-term climate prediction to aid planning and design is also considered. It is concluded that, although current knowledge is not sufficient to support the production of definite long-term forecasts, study of the past record of climatic change is essential if reliable estimates of the potential range of future climatic conditions are to be obtained.