Global warming increases drought severity

Climate science in any real sense is only about as old as I am (as per this bio of one of its founders) and it reached maturity at about the same time I did – years ago, that is. But it is still learning, as I hope I am, and still making important new discoveries. Here’s a very good example, a paper published this month in one of the world’s greatest journals, Nature.

I will quote the Abstract, the authors’ summary, in full:

Drought is one of the most common and complex natural hazards affecting the environment, economies and populations globally. However, there are significant uncertainties in global drought trends, and a limited understanding of the extent to which a key driver, atmospheric evaporative demand (AED), impacts the recent evolution of the magnitude, frequency, duration and areal extent of droughts. Here, by developing an ensemble of high-resolution global drought datasets for 1901–2022, we find an increasing trend in drought severity worldwide.

Our findings suggest that AED has increased drought severity by an average of 40% globally. Not only are typically dry regions becoming drier but also wet areas are experiencing drying trends. During the past 5 years (2018–2022), the areas in drought have expanded by 74% on average compared with 1981–2017, with AED contributing to 58% of this increase. The year 2022 was record-breaking, with 30% of the global land area affected by moderate and extreme droughts, 42% of which was attributed to increased AED.

Our findings indicate that AED has an increasingly important role in driving severe droughts and that this tendency will likely continue under future warming scenarios.

Source: Gebrechorkos, S.H., Sheffield, J., Vicente-Serrano, S.M. et al. Warming accelerates global drought severity. Nature (2025). https://doi.org/10.1038/s41586-025-09047-2

What’s that in plain language?

Most people think droughts happen simply because it stops raining. But scientists have found another powerful force at play. As the air gets warmer, it increases what’s known as atmospheric evaporative demand, or AED.

Think of AED as a giant sponge in the sky. As it heats up, it pulls more and more moisture from the land below, drying out soil, draining rivers, and stressing plants, often faster than that moisture can be replaced.

We don’t know much about whether global warming increases the likelihood of drought, but the authors found that…

…AED has increased faster than precipitation rates, suggesting an alarming tendency towards drier conditions.  … In warm areas, raising the temperature by just a couple degrees can dramatically increase the atmosphere’s ability to draw moisture from crops, rangelands, and forests…

This study reinforces past work showing that droughts will become more intense in a warming world. This has implications for global food and water security, which may in turn amplify political instability and conflict. Easier to see are more direct links between increased AED and wildfire. A thirsty atmosphere desiccates plants, which contributes to larger wildfires.

How science is shared

Those two quotes are from scitechdaily, a respected science news site which takes hard science stories and makes them more accessible. The Conversation does the same, and so do several others.

Scientific discoveries eventually make their way on to the more popular media, often via such intermediaries, at the same time as they are being circulated in the science community.

Sadly, it can take a while before they are properly absorbed, as I said in Too many 1-in-100-year floods in March.

Townsville’s record-breaking 2025 rainfall

Our floods in Jan-Feb were so significant that I compared them to our massive 2019 floods. I should have waited, as it turned out, because they were followed by another drenching, 995 mm from March 10 – 28. By that point we had collected a swag of all-time rainfall records…

  • Highest rainfall in a wet season: 3100 mm (approx, depending on the definition of the wet season)
  • Highest December rainfall: 487 mm (prev. 458 mm in 1975)
  • Highest February rainfall: 1198 mm (prev. 961 mm in 2009)
  • Highest March rainfall: 1005 mm (prev. 696 mm in 2011)

…and another was within sight. Continue reading “Townsville’s record-breaking 2025 rainfall”

Too many 1-in-100-year floods

A conversation

In the wake of our 2025 floods (Jan 28 – Feb 12), North Queensland Conservation Council posted a call to action on facebook. I agreed with it and then tried to say why the “1-in-100-year event” label has become so obviously misleading.

NQCC: Floods and heatwaves are the new normal.
North Queensland has been hit hard again, and these so-called “1-in-100-year events” are happening way too often. Climate change is making extreme weather more frequent and intense, yet our leaders still aren’t taking the urgent action we need. …

Malcolm Tattersall: “1-in-100-years” is a (sort of) average and what it really means is that there is one chance in one hundred of such a flood occurring in any given year. But that measure is purely statistical and historical. As such, it relies on the future being like the past, and climate change has completely undermined its validity.
The calculation is really very simple – too simple, in fact, to include any of the changes (e.g. urbanisation, dam construction, climate change) which might make nonsense of the prediction.

That was enough for facebook but pursuing the science further seems worthwhile.
Continue reading “Too many 1-in-100-year floods”

Townsville floodways

Townsville is built on a floodplain. From a distance the whole city looks flat, with a few very obvious bumps: Mt Stuart and its foothills, Castle Hill and Mt Louisa. But the flat area is not quite flat.

Early settlers built on the (slightly) higher areas, avoiding the mudflats and mangroves, and formed their roads on the (low) ridges, leaving the (shallow) gullies and creeks alone. Over the 150 years since, low spots have been built up, and watercourses deepened and straightened, as urbanisation encroached on the lower ground. But the natural drainage network persists, as we realise (often unhappily) whenever we get a lot of rain.

An overview
Map of Townsville watercourses
Townsville watercourses, Castle Hill to Mundingburra

Continue reading “Townsville floodways”

Resilience

We’ve just had our first real wet-season rain, foreshadowing the approaching cyclone season. It’s a reminder that our weather is getting less predictable and more dangerous to ourselves and our cities.

We can’t do much about that, although we should still do what we can, but at least we can cultivate a more resilient lifestyle. This is not about going into full ‘prepper’ mode, with a bunker in the back yard and a tinfoil hat, but about making minor and generally painless adjustments to how we go about our daily lives.

Some of them look quite old-fashioned but there’s a reason for that.

Continue reading “Resilience”