00:01Now, high temperatures and hot weather can be deadly for humans, but scientists looking
00:07at six extreme heat waves in the last two decades have found that it's the elderly who
00:12are most vulnerable.
00:13That's right.
00:14This study was published in the journal Nature Communications, and we're joined now by the
00:18lead author, Professor Sarah Perkins-Patrick, who's a climate scientist at the ANU.
00:24Just talk us through, Sarah, what the factors were that you looked at in this study that
00:31made heat waves so deadly, because it's not just the heat that we're talking about.
00:35No, that's right.
00:37Often it's the combination of heat and humidity that can make heat waves particularly deadly.
00:42So we're talking about temperatures in the mid to high 30s, mainly the high 30s, coupled
00:46with really high humidity that can be deadly.
00:48But what we also realised in this particular study, that you can also get heat waves that
00:53are very high in temperature.
00:55So the high 40s, maybe even sometimes they can breach the early 50s, and that coupled
01:01with low humidity, they can often be just as deadly as the hot and humid ones.
01:05You looked at six extreme heat waves between 2003 and 2024.
01:10What were the conditions like in those heat waves?
01:13Oh gosh, it depended on what exactly the heat waves we were looking at.
01:17No two heat waves were the same.
01:19We chose these six heat waves because they were phenomenal in either the records they
01:24broke climatologically or dependent on how many people were reported to have died during
01:28these events.
01:30So each of these heat waves had a different profile.
01:32They occurred over a different part of the world.
01:35We looked at events over Australia, for example, one in Europe, one in Southeast Asia, one over
01:42the Middle East in 2024.
01:43And they all had different combinations of temperature and humidity, that none of them were the same.
01:48But like you said in your opening statement, all of them had a signature that if elderly
01:52people were outside during these events for at least six hours, then they would have been
01:57at grave risk.
01:58And what makes older people particularly vulnerable when we're talking about extreme heat here?
02:04Yeah, that's a really good question.
02:05The main thing is, as you reach your older ages, so in our study we looked at people over 65,
02:11your ability to sweat becomes much more limited.
02:14And sweating is one of our main mechanisms to stay cool.
02:17So as I'm sure we're all aware, when we get really hot and bothered, we do perspire.
02:21The evaporation of this off our skins is what keeps us cool.
02:25But if you're not sweating, you can't cool down by that evaporative process.
02:30And equally, if it's humid, there's nowhere in the air for that sweat to evaporate too.
02:35So that's when it's really humid and you feel like you're just not cooling down.
02:39And older people are just, because they can't sweat, they're just far more susceptible
02:42to the hotter temperatures.
02:44How should this research change the way we view risks associated with heat waves?
02:49Because I wonder if we underestimate those risks sometimes.
02:52Oh, look, absolutely.
02:54Like one of the heat waves we looked at was an Australian one in 2019.
02:57And this sort of deadly area was in the middle of Australia where it's very sparsely populated.
03:03But it just goes to show that nowhere is safe.
03:06And the way we've measured deadly heat waves before is using a much higher threshold that
03:11combines temperature and humidity only.
03:13But what we've shown in this study is when we actually use thresholds based on how humans
03:17work in terms of our physiological makeup, these events are already occurring at a much
03:23lower threshold than we previously thought.
03:25So moving into the future, you know, we're expecting if we're having these events now,
03:29and some of these events date back to two decades ago, unfortunately, they're only going to become
03:35more prevalent as the climate continues to warm.
03:37I was going to say, what does this mean then for the warming climate?
03:40And what should our response to findings like this be?
03:43Not just in Australia, of course, but the global response?
03:46Yeah, look, absolutely.
03:46And, you know, it was a global study, so there should be a global response.
03:50Basically every inhabited continent will be susceptible to these sorts of events.
03:55Some already are more than others.
03:56But we need to make sure that we're putting the appropriate adaptive mechanisms in place.
04:00So what we did mention in this study was using the example of the heat wave over the Middle
04:05East in 2024, 1,300 people did die.
04:09But there were a lot of strategies put in place to strongly encourage people to stay indoors
04:14during these deadly heat events.
04:16And for the vast majority of people, it did work.
04:19So simply by seeking shelter, by educating the public, by telling them how they can avoid
04:23the heat, that goes a very long way in safeguarding these populations.
04:28So we do need to have a better and stronger adaptive capacity.
04:31In some of the countries that we analysed, we likely underestimated how many people did
04:37die during these events.
04:39So we do need to make sure we're capturing those numbers more appropriately so we can better
04:43adapt in the future and know what we need to do for those populations.
04:46Professor Sarah Perkins Kirkpatrick, the lead author of this study and climate scientist
04:50at the ANU.
04:51Thank you so much for your time this morning.
04:52My pleasure.
04:53Thank you for having me.
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