Weather and climate

While we luxuriate in what’s now shaping as the best Australian snow season since 2000, it’s worth remembering that weather is just the random variations of the climate system … the short term “noise”. One good season does not climate make, any more than one bad one can.

Spencers Creek snow depths for season 2014, from Snowy Hydro Limited

Spencers Creek snow depths for season 2014, from Snowy Hydro Limited


A glib but fair definition of climate is “the statistics of weather”. Statistics because there are many different measures that describe the typical stuff of weather: its variations, its extremes, its changes. But the most important statistic will always be the one in the middle — the mean or “average” — particularly its long term trend. Unfortunately that bit remains woeful, and will stay that way regardless of whether 2014 makes it to 2 m or even 2.5 m peak depth:

Spencers Creek snow depth future


That graph did not just emerge from thin air. It’s based on 60 years of hard physical measurement effort by Snowy Hydro staff in all kinds of conditions, plus a decade of mechanistic prediction work by dedicated teams at CSIRO, the Australian National University and the Australian Bureau of Meteorology. Maybe they’ve all got it wrong, but unfortunately I don’t think that’s likely.

Appropriately interpreted, their combined efforts show one clear result: every year our leaders prevaricate, bluster, delay, hedge, dodge and kowtow to their funders, they steal another two centimetres from our average peak high-altitude snow depth. There will always be better seasons and worse seasons, but the middle statistics — the mean and the median — inexorably decay.

3 comments to Weather and climate

  • Misha

    This is very interesting, despite being incredibly depressing. Did you see 4 corners last night regarding renewable energy? Very interesting, if only.

  • Colin Ridley

    Excellent analysis. Now that Snowy Hydro are doing cloud seeding each winter, it will be interesting to see the incremental increase in these figures. I expect the natural snow cover will continue to decline but there should be a slight step up too. Do you happen to know how much they think they’ll add to average peak depth?

    • Gerg

      Snowy Hydro has been cloud seeding to various degrees for a decade now, so if there was a large effect on snow depth we should be beginning to see it in the data — for example in the Spencers Creek peak depth moving average trace in the second graph above. Unfortunately I see no uptick. (The little dashed extension there is for averaging intervals decreasing from 20 years down to 10 years at the leading end.)

      I don’t doubt that cloud seeding works as advertised, it’s just that “as advertised” means “14% increase in precipitation from selected suitable storms”. That is not 14% more snow depth, not even 14% more total snowfall, it’s 14% more measured precipitation from suitable seeded storms. And you only get to that answer by excluding the experiments you didn’t like (“overall target (not) effectively covered”) … otherwise it’s only a 7% gain from the seeded storms, with, err, 24% probability that that outcome was due to chance alone. Sorry if I sound sceptical. As I said I don’t doubt that it works; just don’t expect a huge effect.