With winter snow in the northern hemisphere, we tend to forget the heat that summer brings to the southern half of the world. It can get pretty hot down there. The Guardian reports that Australia is entering the third day of another terrible heat wave, remarkable not just for how hot it is, but how much of the country it covers: basically, all of it.
This is the second killer heat wave to sweep across Australia this year. The memory is fresh of the scorching heat in early January, now it’s back with even more of a vengeance.
On this particular issue, the science is in and it’s clear. Heat waves in Australia are getting more frequent, lasting longer, and getting hotter. This for a continent that’s already a pretty hot place, covered with extensive desert. A country on the brink of heat excess, is plunging in with worrisome speed.
The science is also in, and clear, that the heat waves take a tremendous health toll. The increase in mortality (that means death) during these events is alarming, as are hospital admissions, and only those in deep denial even try to deny it.
I went and got the ACORN data for long-term temperature records in Australia, the Australian Bureau of Meteorology’s best long-term temperature data sets. The first station in their list is the Hills Creek Meteorological Office, and here is their daily high temperature since 1910:
The daily high temperature ranged from 10.7°C (51.3°F) to 44.9°C (112.8°F). It can get very hot.
The time series of average temperature confirms warming at this location, and points to a clear difference between the data before and afeter the year 1985. So, I made histograms of the temperature distributions for those two time spans:
It’s clear that all temperature above 35°C got more likely, and almost all temperatures below that value got less likely. Not only do we have overall warming, we have exactly the kind of notable difference at the extremes (i.e., the hottest temperatures) that makes climate change make heat waves into monsters.
Another way to show this is to use, not the probability density function (pdf, as approximated by a histogram), but the survival functions. It’s the chance of temperature being that high or higher, for all possible values:
Again, the difference is obvious, with high temperatures more likely since 1985 than they were before. An advantage of the survival function is that one can compute reliable probable errors, which easily confirm that the difference is both sizeable and statistically significant.
Yes, heat waves in Australia are getting hotter, happening more often, and lasting longer. Yes, the toll in human life and health dwarfs the economic losses, a huge as those might be.
Australia is vulnerable to heat waves. We can help her, if we all do our best to limit future warming by eliminating carbon emissions. If we don’t, if the worst-case scenarios play out, I dread the heat waves that will plague our brothers and sisters down under.
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