It's not cloud seeding that causes hail and floods

This year the weather in the Emirates seems to have gone crazy. Heavy rains, storms and floods continue to hit the region in recent days, while in February Abu Dhabi experienced one of the worst …

It is not cloud seeding that causes hail and floods in the Emirates

This year the weather in the Emirates seems to have gone crazy. Heavy rains, storms and floods continue to hit the region in recent days, while in February Abu Dhabi experienced one of the worst hailstorms in its history, with hailstones the size of tennis balls that shattered car windows and forced the closure of schools. In the same days, the country's National Meteorology Center announced the launch of 14 flights aimed at cloud seeding operations, a method used to artificially induce precipitation. This has prompted some well-known newspapers, such as Il Messaggero, to write that it is precisely the seeding of clouds that causes extreme hailstorms and floods. Upon closer inspection, this is fake news, and we will explain why.

Cloud seeding, as we were saying, is a technique with which it is possible to increase the probability of precipitation in a relatively limited area. It works by releasing substances within a cloud (typically silver iodide or other salts) that can act as condensation nuclei, i.e. pushing the humidity present in the cloud to condense in the form of drops and thus starting rain. There are different positions in the scientific community on the real effectiveness of these techniques (after all, it is difficult to establish a posteriori what would have happened to a cloud if it had not been seeded), but to work they need very precise conditions: that is, clouds must be present with the right amount of humidity in which to release the condensation nuclei. Without clouds, on the other hand, there cannot be rain, and cloud seeding cannot create rain from scratch, but only increase the probability or intensity of precipitation.

The weather of the Emirates

With this background, what is happening to the climate of the Emirates, and what is the role of cloud seeding? First of all, it is true that the climate in those areas is traditionally arid, so much so that the United Arab Emirates has been working on cloud seeding projects since the 1990s, precisely to try to increase rainfall, and therefore the quantity of water available on the ground. That it usually rains little, however, does not mean that it never rains, or that when it rains the precipitation is scarce. On the contrary. “When it rains it is generally not rain but very heavy rain, because we are talking about an area between subtropical and tropical,” Giulio Betti, Cnr climatologist, explains to “It means that there is always strong energy at play and this is because the Arabian peninsula overlooks the Arabian Sea which is an area where cyclones sometimes form, which then generally affect Oman, between June and October”.

natures 2017

Well before the cloud seeding and climate changes we see in recent decades, storms and floods periodically affected areas of today's United Arab Emirates. The most devastating of the last century dates back to 1963, but they were also recorded in 1948 and '49, and before that in 1883, 1884, 1886 and 1912. Storms have never been lacking, therefore, and are produced by meteorological systems of very large scale. And not from phenomena that occur on a local scale, such as cloud seeding.

“Cloud Seeding is a small-scale system and not a mesoscale system,” added Betti. “Cloud Seeding does not work on a storm system tens of kilometers across, but only at a specific point. The floods we have seen in recent months or in recent years are not related to Cloud Seeding. It's absolutely impossible. This is because they were all linked to the mesoscale system, that is, very complex systems that led to disastrous floods.”

Climate changes

In the future, Saudi Arabia and the United Arab Emirates are destined to experience extreme weather events and floods more and more often, because they are among the areas where an increase in temperatures and heat waves is expected due to ongoing climate change. And on the other hand it is a phenomenon connected to what is happening here too: in recent years the winters have always been little rainy (and risk becoming less and less in the future), and this increases the chances of seeing heavy rains in the Arabian desert .