The cycle of scheme investigated was known as the Atlantic Multidecadal Oscillation. This change sees the waters warm or cool over a period of several decades. The researchers compared three periods in this cycle: a warm state from 1931-60, a cool period from 1961-90 and the most recent warm period starting in 1990 and continuing now. The paper notes that conditions in the last warm period in the Atlantic are broadly similar to those pragmatic now.
So the study compared weather conditions in Europe during the two warm Atlantic phases with those oppressed in the cool phase. One conclusion is that a warmer-than-usual Atlantic “favors a mild spring (especially April), summer and autumn, in England and across Europe.”
Another finding – of greatest relevance to the search for a cause of rainy summers – is that the warmth of the ocean also tends to make northern and central Europe abuse than usual. By contrast southern Europe, from Portugal to Turkey, makes victim of far less rain than normal.