Abstract
A 133-year length (1883–2015) daily climate record from Sheffield, England (53.38°N, 1.49°W) is analysed. Across the entire length of the record, there are significant warming trends annually and for all seasons, whereas precipitation shows a significant annual increase but the seasonal trends, whilst all positive, are not significant. Trends in extreme indices mirror the mean long-term warming and wetting signal. Record hot and cold daily temperatures and precipitation amounts are associated with summer anticyclonic conditions, an anomalous easterly winter jet stream and summer cyclonic activity, respectively. Whilst there are large uncertainties surrounding the calculation of return periods for the daily maximum, minimum and precipitation records from a single record, our best estimates suggest that in the current climate (2015), the existing records have return periods of 38, 529 and 252 years, respectively. The influence of several climate indices on mean and extreme indices are considered on seasonal scales, with the North Atlantic Oscillation displaying the strongest relationship. Future mean maximum temperature and precipitation alongside extreme indices representing the warmest and wettest day of the year are analysed from two downscaled climate model output archives under analysis periods of a 1.5 and 2 degree warmer world and the 2080–2099 end of 21st century period. For this mid-latitude location, there is minimal difference in model projections between a 1.5 and 2 degree world, but a significant difference between the 1.5/2 degree world and the end of century 2080–2099 period under the most severe climate warming scenarios.
Highlights
Several unusual and extreme weather events and periods have occurred across the United Kingdom (UK)
The thresholds for the 95th and 99th daily precipitation percentiles are 18.2 and 31 mm·day−1, respectively. This presents a somewhat curious difference between the long-term R20mm trend and the R95p trend (29 mm·century−1, Table 6), which is mainly due to the different units—R20mm requires an increase in frequency of “very heavy” precipitation days, whereas R95p does not—but we find a non-trivial number of days (183) where precipitation was between the 18.2 and 20 mm threshold, highlighting how careful selections must be made when determining thresholds for analysing “moderate” extreme events (i.e., ~one year return period)
Global warming has contributed to an increasing likelihood of warm and wet extremes and decreasing likelihood of cold extremes
Summary
Several unusual and extreme weather events and periods have occurred across the United Kingdom (UK). Since the end of the 20th century there have been a greater proportion of warm and wet UK climate records broken and much fewer cold and dry records broken [11]. The clustering of these recent unusual and extreme phenomena raises the question of whether or not UK weather extremes are significantly responding to Climate 2016, 4, 46; doi:10.3390/cli4030046 www.mdpi.com/journal/climate anthropogenic global warming, or whether natural variability is the dominant force in a geographic dominant force in a geographic location with highly variable intra-seasonal weather and climate location with highly variable intra-seasonal weather and climate conditions
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