Just how extreme can ‘extreme’ weather get?

For some years now I have been grappling with the possibility that global warming just could, just might, ramp up in some kind of mad accelerative way, and fry us just as we were about to drown because of sea-level rise of an unmentionable height. OK, it’s unlikely, but some people think it just might happen, and that is why we have precautionary principles, carbon taxes and RETs. Somebody believes this kind of stuff, and though I’m not one, I’m agnostic enough to be prepared to accept it if the evidence were to hove in view.

Somewhere along the way I came across a paper which seemed to suggest that the temperature of the oceans had an upper limit. I think it was around 37 degrees Celsius. The Red Sea has a maximum temperature of 36 degrees. I cannot now remember why there was thought to be an upper limit, but plainly, the hotter the water gets, the more of it will evaporate, the more evaporation, the more rain, the more rain, the cooler it gets. No matter. I’ve searched and searched and cannot find this reference. Maybe a reader will oblige.

But Judith Curry ran a most interesting article in her Climate etc website about the question of limits to extreme weather, and the original set of slides by Greg Holland, an Australian who works at NCAR, is well worth downloading. A quick summary is that as temperature rises what might happen is not that the extremes get more extreme, but that there are more warm days, no more intense hurricanes but more smaller ones, and so on. You can get a feeling for the change by looking at the following two graphs.


What you see here on the left-hand side are the graphs of hot days per month over time, beginning with October, then November, then December  and then January. As time goes on, what happens at this Central Australia weather station (Giles) is that the number of hot days increases, and that the temperature of the hottest days increases too. But the maximum temperature does not. It sits at 46 degrees Celsius.

Now the same trend can be seen in Melbourne, a long way from Giles, but subject also to extremely hot days. The maximum in Melbourne, too, over these years, has been 46 degrees Celsius. Climate change (I don’t know from the Power Point slides how he defined it) has no greater effect. Indeed Holland suggests that all the effects of ‘climate change’ may have already occurred. From that I deduce that he thinks that the increases in temperature are largely aspects of ‘natural variability’, whatever that is.

I add the rider because soon or later someone has to come up with a theory about what the components of natural variability are. It is easy enough to pick holes in the orthodox AGW arguments, but my own intellectual curiosity requires appeasement too. What mixture of factors produces these ‘natural’ changes? OK, they seem not to be caused by human activity, but exactly what does cause them?

There seem to be limits to what can happen in the world of atmosphere and oceans, and while that is reassuring. I would like to know why these limits are what they are. Judith Curry attended the seminar at which Holland’s paper was given, and says that he had a sophisticated explanation. It would be good one day to be able to grapple with it.

In the meantime, my current position is that we are not in fact seeing more extreme weather. Holland doesn’t think there are more tornadoes, either, and while North America has had a long cold autumn and is experiencing snow and extreme cold in June, that too is just weather, and not ‘extreme’. It has happened before, just as we have had mild winters before.


Join the discussion 13 Comments

  • Dave Barnes says:

    I had understood for many years that SST cannot rise above somewhere between 32 degC and 33 degC on a synoptic scale because therein lies a point at which incoming solar energy is matched by losses due to evaporation.

    Willie Eisenberg has a more complicated take on this suggesting the maximum possible SST is slightly lower:


  • David says:


    I like this post. IMO your best ever. Well argued and reasoned. You consider all sides of the argument. Well done!

  • margaret says:

    There seemed to be alarm generated about the fact that a mild autumn had affected the chances of good skiing for the the winter, the June long weekend being the ‘official’ opening of the ski season. That seems ridiculous to me. I’m not a skier but my sister is and she would never have gone to a ski resort in Australia in the month of June. Then, as June progressed some snow fell, dispelling the fear that none would come!
    I mention that just as an example of the sort of notions the general public is fed and why people become lazy and reactionary in not thinking about, but just accepting the ideas seeded that these things must indicate anthropogenic global warming when they are just variations in the weather.

    • margaret says:

      I’m adding to this comment as the ‘common wo/man’ who has become a little more interested in an issue that formerly she just let wash over her and fill her with unquestioned assumptions.

      If weather reports were not so dumbed down and actually provided some of the data about the AGW debate as an adjunct to the daily report at the end of the news it would help inform those whose lives and interests preclude intensive research into it.
      But I have taken a long time to realise that the powers that be in all walks of life really don’t want a populace of educated critical thinkers. The developing oligarchy suits them perfectly.

    • John Morland says:

      I have just come back from Thredbo, the snow up high was fantastic (over a metre thick),Thredbo in the valley had stack of snow lying around. Unfortunately it drizzled over two nights and a fair bit of the village snow melted, but up higher it contunued to snow, THh weather over the last 3 days on the slopses was cloudy, windy and (at times wet./snowy). Another huge cold front is coming this week-end – the local are clling it snowzilla.

      Yes, you can be lucky in June. I still remember an AGW alarmist assuring me in 1988 that there will be no snow in the snowies within 20 years. Jeez I wonder what he is thinking now – I know, exactly the same : the snowies will have no snow within 2o years!

  • Gus says:

    I don’t know how your authors arrive at their projections, but climate models generally predict little change for tropics and subtropics, other than the spread of the jungle, that is, “the wet” north and south, away from the equator–and this has been observed in semi-arid regions of the Southern hemisphere, including Australia, also in the Sahel. It is the polar regions that warm up more significantly in the models. Because the weather, with its extreme events, is driven, generally, by the temperature difference between the equator and the poles, as this difference becomes less, there is correspondingly less driving, therefore the weather gets milder. It’s elementary physics, the Carnot engine, in action.

    This is confirmed by observations. First, there is no sign of any increase in the frequency or intensity of catastrophic weather events, throughout the whole warming period, that is, the past 150 years or so, and throughout the world. This means that whatever warming has transpired it’s been way too little to make any difference to the world’s climate system and the weather. Second, palaeoclimate data tells us that there hasn’t really been any change at all in the tropics. For example, Vasquez-Bedoya et all find in Paleoceanography, 2012, that the tropical Atlantic sea surface temperature remained constant to within 1C during the past 225 years, doi:10.1029/2012PA002313. This is based on the coral data sampled off the north-eastern Yucatan peninsula. Closer to home, Haig et al found that the tropical cyclone activity in and around Australia is currently at the lowest in perhaps up to 1500 years, Nature 2014, doi:10.1038/nature12882.

  • Mike O'Ceirin says:

    The answer is very extreme from time to time but not every where at once. I have Lamb who chronicled the extreme weather of the past. Towns buried in sand, washed in to the sea, encroached on by a glacier, half an island disappearing, months of solid rain one year Europe lost summer. These are events in recorded history which are relatively a short time ago. A good source for recent times is http://wattsupwiththat.com/reference-pages/climatic-phenomena-pages/extreme-weather-page/ EWE seems to be in decline so lets not bleat about it.

    • John Morland says:

      The Moche society (early 8th century in South America) had 30 years of flood followed by 30 years of drought due to a massive El Nino followed by an equally massive La Nina.

      Imagine if that happend today – proof positive of CAGW.

  • Nicole Parton Fisher says:

    Allow me to add my voice from “North America.” To quote you “… while North America has had a long cold autumn and is experiencing snow and extreme cold in June,” North America is a pretty big place. You wouldn’t let such a broad statement whistle by in the classroom! I live in Vancouver, Canada. Our autumn was brilliant. Precision please, Dr. Aitkin!

    I checked the US snow report this week and found precisely two ski resorts – each at high elevations – that had received a 12 cm of snow. Snow is not unusual at any time of year in British Columbia’s Coastal range and in the Rockies of Alberta. While I cursorily examined only the snow fall and glaciation in 2013 and 2014, they look pretty much the same to me at http://www.climate4you.com/SnowCover.htm#Recent%20USA-Canada%20snow%20cover

    The credibility of that website or of the charts shown is for others far smarter than I to determine, but I’ve heard no alarm bells on the local or national news concerning snow reports. What I have seen with my own eyes is the severe and rapid retreat of glaciers in the Columbia Ice Fields, in the Canadian Rockies. I understand that while one swallow does not a summer make, many mid-latitude glaciers are shrinking.

    That I find of far greater interest than a light snowfall at two American ski resorts and a chilly autumn somewhere in North America.

    • David says:

      Nice post!

    • Don Aitkin says:

      Ms Fisher, I bow my head in shame. There were in fact more than a few cold readings, and a chap I read had made a list of them. But you are right. ‘North America’ is simply too broad a region to generalise about sensibly.

      But I did say it was just weather!

  • warmair says:

    Climate warming has more impact on minimums than maximums, simply because the hotter something is the faster it radiates energy for example double the temperature and radiation emission goes up by a factor of 16.

    It is has been observed over recent decades that there have been more extreme weather events specifically more heat waves, and probably more extreme rainfall events, higher wind speeds, and more powerful storm surges. Physics tells us that the wind strength of cyclones and hurricanes is critically related to sea surface temperatures every degree over 28C is has a dramatic impact on storm strength and rainfall.


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