For those who live in south-eastern Australia, the change has been noticeable – summers aren’t what they used to be. As a Melburnian, that’s certainly been my perception anyway. And – perhaps unusually for me – that perception is backed up by facts.
In this case, the perception is that we’re having far more warm and humid days than in past summers. Is my perception of higher humidity real or imagined?
In fact, data shows that the entire eastern seaboard of Australia has seen an increase in humidity recently. For ‘weather heads’ like me, it’s an interesting change in our traditional seasonal patterns. But an increase in humidity has other implications, too, in particular for our health.
High humidity can present some dangerous scenarios, with older Australians very much in the firing line.
The danger of humidity
Back in the 1980s, when I was in my early 20s, cricket dominated my life. I’d play all day on Saturdays, and train for hours at least twice a week. Hot weather? Not a problem. On a 40-degree afternoon I was in my element. I would even wear a sleeveless sweater when bowling to try to ‘psych out’ opposition batters.
I was fit, young and silly, of course. The other thing in my favour was that on 40-degree days in Melbourne the air was almost always dry. I didn’t know it back then, but the lack of humidity made things much easier.
Fast forward to 2009 when, after nearly two decades away, I returned to playing competitive cricket as a 44-year-old. While I settled back into old routines pretty quickly, I noticed a couple of changes. Firstly and unsurprisingly, I wasn’t quite as quick and agile as I’d once been.
The second thing I noticed was our cricket association’s ‘Playing Conditions’. These involved a number of rules around health and safety. No such things existed 25 years earlier, but their inclusion now is not a bad thing.
Those rules incorporated weather. If the temperature rose above 38°C, play would have to cease. “Disappointing but fair enough,” I thought. But there was another, more complicated rule. It mandated a stop in play even at lower temperatures if the humidity was above a certain level.
I thought this was a little bit much, until one day I played on an afternoon that was not overly hot but very humid. I found myself really struggling as the afternoon wore on. Was this old age? Not according to my younger teammates. They, too, would struggle on warm, humid days.
The new humidity normal
In the summers since, I have played on many more such days, and fewer hot and dry days than in the ’80s. Such days are a struggle but they’ve become pretty regular affairs in Melbourne.
In Sydney, a similar change has unfolded. Being further north than Melbourne, Sydney has always been slightly more ‘tropical’, but it too has changed. Sydneysiders have noticed it being “more like Cairns” more often.
Humidity is simply water in its gaseous form held in the air after evaporating from liquid water or ice. That extra water in the air has a number of consequences. As well as slowing down the drying of your clothes on the line it makes you feel hotter.
The reason eastern Australia has experienced more humidity in recent years is our old ‘friend’ climate change. To date, over 90 per cent of the extra heat trapped by fossil fuel burning has gone into the oceans.
Accompanying this, the amount of water vapour over the oceans has increased by roughly 5 per cent in the industrial era. This is in “lockstep with global warming”, says Steven Sherwood, professor at the Atmospheric Sciences, Climate Change Research Centre, UNSW Sydney.
What makes it dangerous?
This is why on a moderately warm but muggy day I struggle on the cricket field, ending the day exhausted. On the hotter, drier Saturday afternoons I feel the heat but don’t get anywhere near as exhausted.
It’s all about sweat. Your body’s natural cooling system in hot weather is evaporation of sweat. Sweat forms on your skin, the air evaporates it and the heat leaves with it. But in high humidity, when the ‘dew point’ rises, our bodies struggle. The evaporation of sweat becomes more difficult when the surrounding air is already moist.
The danger comes with heat stress, which is a more likely outcome in high humidity.
It seems that more frequent warm and humid days is the lot of Australians across the eastern seaboard. With that in mind, we will need to adapt on such days to ensure we stay safe.
Have you noticed a change in recent summers in your area? How does humidity affect you? Let us know via the comments section below.
Also read: How to prevent insect bites as the weather warms up
Health disclaimer: This article contains general information about health issues and is not advice. For health advice, consult your medical practitioner.