A phenomenon that made the recent California wildfires so damaging is spreading further afield.
Climate “whiplash” sees dangerous swings between very wet weather and very dry weather.
Drought or extreme rain are hard enough to contend with on their own. The problem with whiplash is the severe jerk from one to the other makes them both more damaging.
It bore out in Los Angeles when two very wet winters produced lots of grass and shrubs, and were then followed by a long, hot summer that dried out that vegetation, providing abundant, tinder-dry fuel ripe for a wildfire.
Without this swing “there still could have been severe fires, but this was definitely an event that was amplified by that particular sequence”, says Dr Daniel Swain, climate scientist from University of California Los Angeles.
Heavy rain will slide off scorched earth more rapidly, leading to landslides and flooding.
Keeping reservoirs full should help guard against drought – but sudden, heavy downpours can send them overflowing, flooding the surroundings.
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How is whiplash changing?
A little bit of this whiplash is natural. But scientists are newly talking about it as climate change is making it worse in locations all around the world.
That’s because the atmosphere works like a sponge: it can both soak up and release water. The hotter it is, the more water it can soak up – and unleash too.
So climate change, by warming the atmosphere, is essentially growing the size of the sponge – exponentially, too.
New research by the charity WaterAid has identified at least 17 major cities where climate whiplash is getting worse, out of 112 they analysed (the world’s 100 largest plus 12 more where it works).
While the recent Los Angeles wildfires may be burned in our memory, there are other places that are much more vulnerable.
Partly because they are not fabulously wealthy like the rich and famous of Hollywood, with poorer people and infrastructure, but also because the swings are more extreme.
Take Hangzhou in eastern China, for example, which topped the list of cities with intense climate whiplash. The higher and darker the spikes in the chart, the more intense the weather.
Or Jakarta, second on the list – just look at how dark, wide and tall those wet and dry periods are on the right-hand side.
Impacts in Indonesia’s capital have been “escalating”, with disasters on course to get more frequent and severe, says Egi Suarga, climate manager for World Resources Institute Indonesia.
This threatens food security, adds Prof Cedric John from Queen Mary University London, who has been working with Indonesia’s Bureau for Meteorology, Climate, and Geophysics (BMKG).
“The uncertainty in the timing and intensity of rainfall, as well as the prolonged drought, can lead to crop failure or poor harvest.”
WaterAid’s chief executive Tim Wainwright says: “It affects people’s health. It affects education. It affects people’s livelihoods. In extreme cases, it will take people’s lives.”
Where could whiplash strike next?
Partly what makes whiplash so dangerous is its unpredictability. It’s hard to prepare for.
But Dr Swain says there are “early indications” of a particularly hot and dry start to summer across much of western USA, following relatively wet periods, “opening the door to a potential wet-to-dry whiplash event”.
Whiplash isn’t affecting everywhere yet. In fact, in London the extremes may have calmed for now, found WaterAid, which worked with scientists from Cardiff and Bristol Universities to produce these new metrics.
And places like Cairo have ‘flipped’ completely, going from long-term wet to long-term dry.
But eventually the whiplash phenomenon may spread everywhere as the air keeps warming due to climate change.
“We do, in fact, expect that almost every populated inhabited continent on Earth will eventually see a substantial increase in that whiplash,” said Dr Swain.
A study by him in January found whiplash has already increased by at least 31% on average across the globe.
Are there solutions?
The best solution would be to stop emitting greenhouse gases. But this comes at a time when the US looks to up fossil fuel energy and row back on overseas funding for climate projects.
The UK has also eaten into its aid budget to pay for increased defence spending.
But solutions are often “very well known and very simple”, says Tim Wainwright.
In Karachi, for example, people harvest water from the sky as it cools, and then us it to wash, farm, or refill dried up wells.
Wainwright says the solution often “does not require a huge leap forward in technology. It requires leaps forward in political leadership and investment”.
