The spring of 2011 has been warm and dry across southern and eastern parts of the UK. There have been many news stories in recent weeks about the problems that the exceptionally dry spring weather has caused farmers across areas of southern Britain and continental Europe. The growth and development of plants makes the weather in spring particularly important to farmers, so changes in spring weather would have large effects on agriculture. I wanted to find out how spring weather in the UK has changed and what future changes might look like.
Gridded datasets of weather observations from 1961 to 2006 compiled by the Met Office show some interesting trends in UK spring weather (March, April and May) over the last few decades (http://ukclimateprojections.defra.gov.uk/content/view/815/500/). All the maps used here can be found on the DEFRA website along with many more. There has been an increase in mean spring temperatures across the entirety of the UK with widespread warming of between 1.4-1.8C across the majority of England and Wales (shown on map below). There have been greater increases in maximum temperatures than minima.
The trend in precipitation observations is more mixed with much of the country only experiencing small increases or decreases in precipitation amounts over the period. However, a considerable increasing trend has been observed across the mountainous regions of northern and western Britain and there does appear to be a small decreasing trend in precipitation amounts in lowland eastern areas. Other plots show a decreasing trend in the number of days of precipitation across most of England (of about 2-5 days) with increases of a similar magnitude in western Scotland, western Northern Ireland and parts of Wales.
The trend in sea level pressure is small, compared with autumn and winter, but with increases over much of England and Wales and a more variable picture across northern Britain. The spring of 2011 seems to fit in with the trend in observations towards warmer and slightly drier weather across southern and eastern parts of Britain, although it has been exceptional nonetheless. The trend in sea level pressure may be indicative of an increase in the strength and/or length of blocking episodes in southern Britain causing a northward deflection of Atlantic low pressure systems.
DEFRA also produce climate projections (UKCP09) under different emissions scenarios for UK climate over the coming decades. Unfortunately they do not publish projections for spring (or autumn) instead focussing on summer and winter. However, it seems likely that springs will continue to get warmer considering the expected warming in summer and winter. If recent trends in precipitation also continue, then droughts may become more common during spring in future, particularly if water consumption in the south and east of England doesn’t decline. Therefore, we might expect future springs to be similar to the spring of 2011 and it seems that farmers and gardeners will need to adapt to changing conditions with less water-intensive crops and plants likely to become a necessity in the near-future.