California’s History of Mega Droughts
By Paul Homewood
You will no doubt have seen the above graphic already. It shows that the current drought in California is not exceptional by any stretch of the imagination.
We know that rainfall levels in recent years, though low, are not unprecedented as far as the 20thC is concerned.
But, of course, one factor in determining the severity of drought is temperature. To put recent temperatures into historical context, it is worth revisiting the work of V C La Marche & V Markgraf, both experts on past climate.
As shown by HH Lamb in “Climate History and the Modern World”, they studied the height of the upper tree line in the White Mountains of California.
Their data shows just how much higher the tree line was in the Middle Ages, and before, and therefore how much higher temperatures were.
The reality is that California has been hotter and drier for much of its recent history.