Since power output is proportionate to the cube of the wind speed , even such an apparently small variation can result in a 15 % change in a wind farm 's generating capacity .
As philip hammond , britain 's defence secretary , argued last week : " too many countries are failing to meet their financial responsibilities to nato , and so failing to maintain appropriate and proportionate capabilities . "
The threat of cyber-warfare is so new that there is , as yet , no consensus on how to define a cyber-attack , or what would constitute a " proportionate response " .
