It's not just the heat...

An interesting study was recently published this week in the journal Nature. The study showed that yet another affect of man-made emissions of GHG's is increasing humidity. As this article from the Associated Press notes.. "it's not just the heat, its the humidity".. an ironic cliche. The study notes that humidity will raise 6% with every 1 degree raise in temperature. The 40degree humidex they had in Toronto last week starts to make a little more sense now, doesn't it?

Humidity plays a large role on the stress that heat causes on the human body. This was more than evident in the record European heat wave of 2003 that caused over 35,000 deaths; most of which were elderly due to their higher susceptibility to both heat and humidity. Humidity also causes increased evaporation, as well as prolonged heat during the night in urban areas, because of the increased the heating effect on concrete and asphalt structures. Lastly, like many climate change phenomena, it is in itself a contributer to global warming, as water vapour can trap heat in the atmosphere causing yet another vicious circle (similar to the melting arctic ice).

What this article doesn't mention is if the raise in temperature is the only cause of this increased humidity. I wouldn't be surprised if coal and nuclear thermal plants play a large role in adding humidity to the atmosphere. To generate electricity using coal or nuclear, water is boiled into steam which then powers a turbine. Most of this steam then turns back into water and is reheated, or returned from where it came (river, lake, ocean etc). However, about 2L/kWh for coal and 3L/kWh for nuclear is lost as water vapour into the atmosphere. This isn't that huge a problem in Nova Scotia, because we use salt water from the ocean, but it is having extremely negative consequences in Ontario and Alberta, where fresh water is being used. (this steam turbine technology was invented in 1884, in case you wondered about the technology that powers your iPod)

On a very related issue, the Great Lakes are at an all time low, as Ontario plans to bring its second nuclear reactor online and as higher temperatures cause increased evaporation. (here).