On The Seventh (And Sixth) Day God Rested

The forty hour week may be under attack in the United States, but it seems tornadoes still believe in keeping decent working hours. There are a statisically significantly lower numbers of tornadoes recorded on weekends as weekdays in the US.

The explanation appears to be that air pollution is making the tornadoes worse. While many factories etc now run seven days a week, the reduction in car travel etc is enough to see such events drop off once Saturday rolls around.

Daniel Rosenfeld of the Institute of Earth Sciences, The Hebrew University of Jerusalem, and NASA’s Thomas L. Bell have produced modelling that explains why. This is fascinating, but the work isn’t Australian, so why am I mentioning it here?

Well it ties in with a lot of other work. Rosenfeld has also a lot of research into the way aerosols and other forms of pollution interfere with rainfall patterns, and in this area one of the world leaders is Dr Leon Rotstayn of CSIRO Marine and Atmospheric Reaserch. Rotstayn was one of the people who blew the whistle on Global Dimming. The name is a little confusing and has led some people to think it is the opposite of Global Warming, but while these pollutants do have a cooling effect, the dimming is something else. Certain pollutants lead to less sunlight reaching the Earth’s surface, which in turn affects evaporation rates, growth of plants and probably other things.

However, the most significant effect is that rainfall patterns are changed. Aerosols do not mix as well as carbon dioxide in the atmosphere, partly because they are larger and partly because they stay up for much shorter periods of time. Consequently, areas downwind of cities have much larger concentrations than other regions, and the effect is to distort where rain tends to fall, increasing it in some locations and decreasing it in others.

While some areas benefit, in most cases this is bad. Natural ecosystems and human societies have adapted to particular climatic conditions. In some cases they would love more rain (or even occassionaly less) but far more often any change takes them away from their optimum. In time they will adapt, but usually far longer than anyone would like. It is likely that the horrifying droughts in north and east Africa over the past few decades, the cause of literally millions of deaths, have been driven in part by changes in aerosol patterns from Europe, thousands of kilometres to the north.

From what I can see Rosenfeld’s work has looked at this on a finer scale, looking at the way aerosols reduce rainfall over hilly areas nearby. This is of particular concern in the Middle East, where rain is so desperately scarce that lack of water is one of the driving forces for conflict in the region – as if more excuses were needed.

The obvious takehome message is that we need to slash aerosol production (some aerosols are produced naturally by the way, so it is not something that needs to go to zero). However, care needs to be taken. Since the climatic effects are largely the result of uneven distribution of aerosols there are concerns that cutting back in some places and not others could actually make things worse. Since aerosols contribute to respiratory disease, and are usually assoicated with larger particulates that contribute even more, developed nations have been cutting back by forcing the use of cleaner fuels. If this occurs while the developing world speeds up production the negative effects might be substantial, so better models that tell us where to prioritise reductions are vital, something these scientists are working on.

I also wonder whether this might not be a good way to spread the word about Global Warming as well. Tornadoes are most frequent in the US Widwest and South – the heartland (pun intended) of climate denialism. If locals there come to accept that the pollution that belches from their tailpipes and factories is driving an increased danger of being blown over the rainbow, the might be a little more receptive to the concept that other forms of pollution could be changing the global climate on a larger scale.

I’ll also throw in a note some of my readers will really hate. I have no idea where Rosenfeld stands on the question of a Palestinian State or mistreatment of Palestinians. Perhaps he has made some public statements, but more likely not. However, under some of the more extreeme versions of the BDS against Israel being hawked around collaborations such as his with Bell would be forbidden unless he has come out and denounced the actions of the current Israeli government. Although it is unlikely that such proposals will ever be widely implemented, it is appalling they are even suggested. This is true public interest research, something that could save tens of thousands of lives, and it is an area in which Israel is a very big player. To exclude collaborations would set such work back very substantially, and would be as likely to entrench the current policies as challenge them.

Although I strongly support Israel’s right to exist, I am horrified by many of the actions of the Israeli state, and these are getting more frequent and worse. Some forms of Boycott, Disinvestment and/or Sanctions may contribute to restoring some sanity, and where this seems likely they should be supported. However, the sort of broadbrush approach being advocated by many in the BDS movement is counterproductive for many reasons, and I find the motivations suspect. I rather suspect the last two paragraphs will get far more commentary than the rest of the post (perhaps than the rest of my blog), which really is not my aim, but I do think it needs to be said.


About Stephen Luntz

I am a science journalist, specialising in Australian and New Zealand research across all fields of science. My book, Forensics, Fossils and Fruitbats: A Field Guide to Australian Scientists is out now through CSIRO Publishing. I am also a professional returning officer for non-government organisations. I'm very politically active, but generally try to restrict this blog to scientific matters.
This entry was posted in Atmospheric Research, Global Warming, Other forms of politics. Bookmark the permalink.

4 Responses to On The Seventh (And Sixth) Day God Rested

  1. Sol Salbe says:

    Sorry Stephen I do take issue with you. I expect a science column to get the days of the week correct,. Surely it should be and on the Seventh day (and the first day of the next week)… As currently constituted it sound particularly silly to a native speaker of Hebrew, the language the Bible was written in, where Sunday is literally First Day.

    • Sorry Sol, I can’t agree. The order of the days of the week is inherently arbritary (as indeed is the choice of seven, though everyone seems to do it). Therefore the appropriate choice is the one used in the local area. Since I was referring to the creation of tornadoes in the US South and Midwest the question is which day they think the week starts on. I actually don’t know the answer to this, but the fact that things like the calender on my mobile phone have Monday as the start of the week leads me to suspect Americans see Sunday as the seventh day.

  2. Jeshy says:

    I’m somewhat confused by what you mean by “aerosol” in this piece. I initially thought you meant aerosol sprays such as fly spray and hair spray which come in cans, but upon further reading I think you’re using the more generalised definition which would include smoke, spray paint, air pollution, and other random natural things like sea spray created by surf waves, and I’m still somewhat vague on whether a cloud comes under “aerosol”?

    Could you give me some more specifics, especially of how much of this stuff is manmade and what categories it comes under (e.g.: industrial pollution, car pollution, natural, volcanoes, etc.)?

    • Hey good to see you back.

      Wikipedia describes an aerosols as a colloid suspension of fine solid particles or liquid droplets in a gas. From a meteorological/climatological point of view they are fine particles that affect the formation of clouds, by giving water vapour something to condense around. Some also reflect sunlight (well they probably all do, but some do it to a significant extent). In some cases this can counterbalance global warming, but in others the global effect is minimal, but the effect on local weather patterns substantial.

      The most famous natural example is the aerosols produced by coral reefs. Spores produced by the coral float to the surface and on windy days are picked up into the air above the reef. For the Great Barrier Reef, and I imagine some smaller ones, this is large enough to greatly increase cloud cover over the reef, which while no doubt bad for tourism protects the coral from getting too hot. There are fears that if the reef declines we could see a vicious circle, where fewer aerosols are produced, leading to less cloud cover, killing off some of the more heat senstive corals, producing less aerosols etc.

      Meanwhile coal fired power stations spit out a lot of aerosols. Enough to partially offset their global warming contribution, but also enough to alter the climate downwind of them. The effects are not always easy to follow. Generally aerosols don’t change the total amount of rainfall, at least not by much, but they can move the rain around a lot. There is a suspicion that the reason northern Australia has got so much more rain in the last couple of decades than previously is that Chinese aerosols are pushing the Indonesian rainfall south onto Darwin and Cape York.

      I don’t like to say anything good about the Australian coal industry, but I understand that Queensland (and maybe NSW) coal is much lower in aerosol producing elements than the stuff they are digging up in China, so there is an arguement that it is better they use our coal than their own. However, I don’t think this offsets the effect of raising prices if we decided to leave at least some of our coal in the ground, and the consequent switch to cleaner sources of energy.

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