We’ve all heard about the Russian wildfires, and the baking summer heat in Asia. I’m a little surprised to find a reasonably good article on the cause of all of this in the New Scientist.
Raging wildfires in western Russia have reportedly doubled average daily death rates in Moscow. Diluvial rains over northern Pakistan are surging south – the UN reports that 6 million have been affected by the resulting floods.
It now seems that these two apparently disconnected events have a common cause. They are linked to the heatwave that killed more than 60 in Japan, and the end of the warm spell in western Europe. The unusual weather in the US and Canada last month also has a similar cause.
According to meteorologists monitoring the atmosphere above the northern hemisphere, unusual holding patterns in the jet stream are to blame. As a result, weather systems sat still. Temperatures rocketed and rainfall reached extremes.
This is all because of an unusual but not unheard of phenomenon where the jet stream just stalls. Without any air motion either on the ground or aloft, things stagnate.
Renowned for its influence on European and Asian weather, the jet stream flows between 7 and 12 kilometres above ground. In its basic form it is a current of fast-moving air that bobs north and south as it rushes around the globe from west to east. Its wave-like shape is caused by Rossby waves – powerful spinning wind currents that push the jet stream alternately north and south like a giant game of pinball.
In recent weeks, meteorologists have noticed a change in the jet stream’s normal pattern. Its waves normally shift east, dragging weather systems along with it. But in mid-July they ground to a halt, says Mike Blackburn of the University of Reading, UK. There was a similar pattern over the US in late June.
Notice they haven’t mentioned global warming yet, because it’s got nothing to do with this weather phenomenon. Well, they couldn’t resist.
So what is the root cause of all of this? Meteorologists are unsure. Climate change models predict that rising greenhouse gas concentrations in the atmosphere will drive up the number of extreme heat events. Whether this is because greenhouse gas concentrations are linked to blocking events or because of some other mechanism entirely is impossible to say. Gerald Meehl of the National Center for Atmospheric Research in Boulder, Colorado – who has done much of this modelling himself – points out that the resolution in climate models is too low to reproduce atmospheric patterns like blocking events. So they cannot say anything about whether or not their frequency will change.
In other words, they don’t know diddly squat. Shit just happens. Someday they may be able to model this with enough resolution to see this kind of micro-detail, but right now, they’re trying to do calligraphy with a paint roller.
I guess the attempt to tie it to AGW was mandatory, like how Soviet books all had to have a preface that explains how the book supports the revolution.
Anecdotally, the jet stream in North America hasn’t been doing its normal thing, either. Normally, it heads north in late June, and ushers in a period of glorious bone-dry weather in the PNW that lasts until mid-September. But every five years or so, we get a real crapper of a summer, and this is one of them. The jet stream needs viagra, and can’t get it up and keep it up. I’ve had to run the fan about twice, and have damn near had to start burning firewood in the stove a couple of mornings. So something unusual, but not terribly unusual is going on in North America with the jet stream as well.
In the past, we used to say “shit happens”. Now we say “billions will die!!!!!11”. They call that progress.
Tags: Shit Happens, Weather
