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Scientists react to claims that Dubai flooding was caused by cloud seeding.
Dr Edward Gryspeerdt, Imperial’s Grantham Institute for Climate Change, said:
“I would suggest it is relatively unlikely that this storm was due to cloud seeding.
“Cloud seeding aims to enhance rainfall (or snowfall) from susceptible clouds. Not all clouds are suitable and you cannot create a cloud or rain from nothing. You need a cloud that is close to forming rain anyway that you can then ‘tip over the edge’ into rain. You are only modifying an existing cloud (again, you cannot turn a small cumulus cloud into a towering thunderstorm just through cloud seeding). The effectiveness of cloud seeding is very difficult to determine. Once you seed a cloud, you don’t know whether it would have rained anyway. As the clouds you are looking to seed were close to raining already, it is difficult to be sure what the impact of the seeding was.
“Climate models suggest that the maximum one-day precipitation is likely to increase over this region (although there is disagreement between them). All else being equal, you would expect warmer air to hold more moisture, which can lead to more intense thunderstorms. Recent studies of Arabia have suggested increase in extreme precipitation are expected as the world warms.”
Prof John Marsham, Met Office Joint Chair at the University of Leeds, said:
“There has been a lot of speculation regarding a role of cloud seeding in the recent Dubai floods (cloud-seeding is attempting to alter clouds by adding “seeding” materials to alter the formation of droplets and/or crystals within clouds). This is a distraction from the real story here – that due to our collective failure to phase out fossil fuels we must prepare for unprecedented extremes, which will worsen until we reach “net zero”.
“We know that man-made climate increases extreme rainfall – this is well understood physics as warm air holds more water. A rainfall event such as the one that caused the Dubai floods, which covered a large area and where over Dubai a year’s worth of rain fell in one day, cannot happen without large-scale weather conditions driving enormous convergence of water vapour in the atmosphere and so extreme rainfall. Any possible effect of any cloud seeding in these circumstances would be tiny. This is consistent with the fact that weather models gave a warning of the risk of severe flooding days ahead.”
Dr Friederike Otto, Senior Lecturer in Climate Science at Grantham Institute – Climate Change and the Environment, Imperial College London, said:
“The heaviest rainfall in Dubai for 75 years didn’t happen because of cloud seeding. When we talk about heavy rainfall, we need to talk about climate change. Focusing on cloud seeding is misleading.
“Rainfall is becoming much heavier around the world as the climate warms because a warmer atmosphere can hold more moisture.
“Cloud seeding can’t create clouds from nothing. It encourages water that is already in the sky to condense faster and drop water in certain places. So first, you need moisture. Without it, there’d be no clouds.
“Even if cloud seeding did encourage clouds around Dubai to drop water, the atmosphere would have likely been carrying more water to form clouds in the first place, because of climate change.
“It’s important to note that it would have rained in the region regardless of cloud seeding.
“If humans continue to burn oil, gas and coal, the climate will continue to warm, rainfall will continue to get heavier, and people will continue to lose their lives in floods.”
Plus these issued earlier by the University of Reading:
Professor Suzanne Gray, Professor of Meteorology at the University of Reading, said:
“Satellite imagery suggests the flooding and rainstorms Dubai were caused by something called a mesoscale convective system.
“Mesoscale convective systems (MCSs) are what we get when lots of individual thunderstorms amalgamate to form a single large high-level cloud shield, typically hundreds of kilometres across, together with a large region of heavy rainfall.
“They are not rare events for the Middle East. A recent published study analysed 95 events that occurred over the southern Arabian Peninsula from 2000-2020 and found that they most often occur in March and April. A previous event in March 2016 caused more than 240 mm of rain in Dubai in just a few hours, similar to the totals being reported for this event. This study also found that these MCSs have increased in longevity over the UAE over this 21-year period.
“MCSs do occur in the UK, but typically just a couple of times a year during the warmer months when they are usually associated with a plume of warm air coming from Spain.”
Professor Hannah Cloke, Professor of Hydrology at the University of Reading, said:
“The pictures of the floods covering downtown Dubai are quite extraordinary. While massive floods like this have occurred in the past, the huge scale and intensity of the rainfall that caused it are exactly what we are seeing more of in our warmer world. If we don’t rapidly curb warming by phasing out fossil fuels fast, we can expect to suffer more of these extreme floods in more parts of the world, more often.
“This is an extreme flash flood. Modern infrastructure in the developed Gulf states is built to withstand these types of events and drain standing surface water away. But with so much rain falling all at once, even carefully designed drainage systems will struggle to cope.
“Looking at the data from GloFAS, the Global Flood Awareness System, which is part of the Copernicus Emergency Management Service of the European Commission, there was very good early warning of widespread floods up to a week ago. This shows just how important it is for early warning systems to be in place in all parts of the world, and for governments, businesses and individuals to know what to do in response to early warnings. Natural hazards like floods only become disasters when people are in the wrong place and the wrong time. Any loss of life due to flooding is tragic, but is very often avoidable if working systems are put in place to keep people safe.”
Professor Giles Harrison, Professor of Atmospheric Physics at the University of Reading, said:
“The UAE does do operational cloud seeding, but there is huge difference between what this can achieve – targeting individual, developing clouds with seeding material released from an aircraft – and the Dubai rainfall, which was associated with a large weather system advancing across the region.
“There is such a fundamental mismatch of scale in the processes involved that I can’t see how the rainfall and cloud seeding could be related. And there would also be no reason to attempt cloud seeding in these circumstances, given the advance forecast of heavy rain.
“An increase in atmospheric moisture with a warmer climate has long been expected to lead to more extreme rainfall events.”
Professor Maarten Ambaum, a meteorologist at the University of Reading who has studied rainfall patterns in the Gulf region, said:
“This was an extremely heavy rainfall event which dumped a year’s worth of rain across a wide area in a single day. This part of the world is characterised by long periods without rain and then irregular, heavy rainfall, but even so, this was a very rare rainfall event.
“These storms appear to be the result of a mesoscale convective system – a series of medium-sized thunderstorms caused by massive thunderclouds, formed as heat draws moisture up into the atmosphere. These can create large amounts of rain, and when they occur over a wide area and one after another, can lead to seriously heavy downpours. They can rapidly lead to surface water floods, as we have seen in places such as Dubai airport.
“These types of intense rainfall events can be made more extreme due to climate change, as a warmer atmosphere will hold more water vapour. Climate scientists have been warning for many years that such extreme events will become more likely in a warmer climate and, indeed, we see this happening around us now.
“The UAE does have an operational cloud seeding programme to enhance the rainfall in this arid part of the world, however, there is no technology in existence that can create or even severely modify this kind of rainfall event. Furthermore, no cloud seeding operations have taken place in this area recently.
“Cloud seeding, as its name suggests, generally involves spreading fine particles into existing clouds into which conditions of wind, moisture and dust are insufficient to lead to rain. In this particular case, there would have been no benefit to seed these clouds as they were predicted to produce substantial rain anyway.
“It’s also worth noting that forecasters, including the Global Flood Awareness System (Glofas) which is run by the European Commission as part of the Copernicus programme, were very accurately forecasting a high risk of floods across a wide area of the region a full week ago. Forecasting systems such as this use detailed observations of conditions in the sea, air and land, and combine them in forecast models to predict future flood events. If these models were predicting that floods were highly likely a week ago, it’s unlikely that humans could do much about it, other than prepare themselves to get out of the way.”
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