As a result of a hot August and a generally dry year, there have been a lot of comparisons with 2005 floating around in casual conversation. What happened then was that a lack of water during the winter and spring followed by a very hot summer caused severe water stress in the vines, causing them to lose the older leaves on the shoots (roughly the basal third). This had two negative effects: it vastly reduced the amount of photosynthesis possible, meaning that the phenolic ripeness of the grapes was very sluggish, and it also left the bunches exposed to the sun. Conclusion: green fruit dehydrated and started to shrivel without ever really ripening. This was particularly bad on the western and south western side of the vines.
But this year is by no means as climatically extreme as 2005. In fact, both 2005 and 2006 were considerably hotter than 2009 for the corresponding month, and indeed had been for every month from April onwards. Furthermore, in 2005 the total precipitation for the agricultural year had not even reached 200 mm by the start of September – we have already had double that this year. – Miles Edlmann