I have already blogged about the Pakistan monsoon floods (Aug 11) which have killed at least 2,000 and driven perhaps 20 million from their homes, and Russia’s worst known heatwave (July 15) which has killed more than 50 people in wildfires, and has doubled the death rate in Moscow through soaring temperatures and acid smog.
So what is the connection? Air movements called Rossby waves are supposed to move through the upper atmosphere, but sometimes they get stuck. That has apparently happened this year, and when they do they trap the weather beneath them.
This has brought persistent high pressure over Russia, and troughs over Pakistan . Once you get this gridlock, the weather tends to be self-reinforcing. So as Russia warms up, the ground gets hotter and drier. Grass, brush and forest starts to catch fire, and the soot that’s produced heats the air even more.
Disturbingly, some scientists say that they are exactly the kind of trends you would expect to see with global warming, and that they will get worse. There’s more detail in an interesting article in the British magazine The Economist. http://www.economist.com/