When the flow is strong, the British Isles experience warmer, more maritime conditions. However, the most probable change in the behaviour of the westerly wind flow in response to global warming is not known. Thus, for three of the climate indicators we have some idea of what to expect as a result of global warming. However, there is no evidence of a persistent trend in the indicator of geographical contrasts in rainfall, nor of increasing rainfall seasonality. The closeness of the relationship is expressed in the Tables by the correlation coefficient r, where r 2 indicates the percentage of the variation in the indictor accounted for by the climate variable.
Most relationships are intuitively obvious.
Thus, hot, dry summers are associated with high rural ozone levels, many insurance claims for subsidence, more domestic tourism, more outdoor fires, a greater incidence of Lyme disease, greater use of irrigation water, low yields of unirrigated potatoes, low summer hay yields, poor health of beech trees, greater insect abundance and late migration of salmon upstream. Mild winters and springs are associated with poor skiing, lower human mortality in winter, early emergence of leaves, flowers, insects and breeding of birds and larger populations of some insects and birds. There are, however, two reasons for being cautious in assuming that the fluctuations in the climate variables are wholly responsible for the fluctuations in the indicators. First, in most cases, the correlated climate variable is the best one we found. Many climate variables were examined and there is always the possibility that the best correlation does not actually reflect a causal relationship.