I’ve been thinking about how lots of the commentary generally in Australia (and elsewhere) about disastrous winter weather in the northern hemisphere ignores how _higher_ winter temperatures can be responsible for catastrophes.
I watched a fascinating doco on ABC a few months back about freezing rain bringing down the Quebec power grid a few years back (1998?). As the temperatures at ground level plunged, the rain continued to fall. Unlike snow, the rain formed a growing hard frozen coating (‘glaze’) on everything it touched – limbs were stripped from forests of trees, roofs collapsed, and kilometres of high tension power lines came down along and their pylons rendered into scrap metal. Roads became impassable by anything but tracked vehicles, and the glaze ice could not be removed by snowploughs. As the power grid came down, Quebec’s citizens began to die in increasing numbers, freezing to death in unheated homes and flats, crushed under collapsed roofs and in vehicle accidents.
Events like this are, however, caused by warm air aloft trapping cold air on the ground. Clouds in the warm air mass form rain drops, which are then supercooled in the last 500 metres or so of their descent. The point being that what is perceived as a cold weather disaster is actually caused by the anomalous presence of a mass of warm air, in the American continent typically originating in the Gulf of Mexico.
Similarly, snow becomes relatively easy to handle at cold temperatures – dry and pliable. An anomalous thaw, or a series of fluctuations in temperature as unstable weather systems pass over, changes the dry powder into a substance with the consistency of concrete, able to be removed only by jackhammer. If thaw water pools and then refreezes it forms a surface similar to that on a skating rink. A disaster similar to the freezing rain event can result. I’ve actually stayed in Moscow over this time of year and the Muscovites all rejoice when the temperature falls below minus 10 and getting around becomes easier.
The point of all of this is that it’s actually quite easy to misperceive the symptoms of global warming as signs of cooling. Disastrous winter weather can often be attributed to warming.
is bloody good. It is comment number four under this post at Larvatus Prodeo, an Australian site.