Scientists predict summer heat from previous season

A French and Swiss team have developed a method of predicting summer heat depending on the weather the previous season. They found summer heat in Europe rarely develops after a rainy winter and spring in southern Europe and that dry seasons are followed by either hot or cold summers.

It is therefore likely that a drying of southern Europe, as is likely to happen according to climate projections, would predispose Europe to more summer heat waves. The study is to be published in Nature Climate Change.

Summer heat waves have become much more common in recent times, with major events in 2003 and 2010; some consider these as signs of the kind of summers we should expect in the future. The important aspect of this study is finding a means to predict summer events more easily and further in advance. From a database of 200 meteorological stations and 60 years of data, the study found rainy winters and springs generally inhibited the creation of heat waves during the summer.

It is thought a key reason for this is that after a wet month, much of the suns energy is used in evapo-transpiration, whereas after dry months, the heat is transferred to the atmosphere more easily. This means that even a dry winter, followed by a month of heavy rainfall, could lead to a summer without extreme temperatures. The study also looked at how well current climate models show these relationships; most reflect the changes as expected, but not with such clear links.