While the UAE is lucky enough to enjoy almost endless sunshine, rainfall levels sometimes fall short of what would be ideal.
This is despite sporadic spells of wet weather, such as experienced this week, which often occur in the winter months.
As a result, the country has limited water resources and has invested heavily in desalination plants and put significant demands on aquifers, underground rocks that contain water.
To help provide much-needed rain, cloud-seeding operations are carried out, with particles released into the air to help encourage precipitation.
A study published last month highlighted an altogether different method of encouraging rainfall in the Emirates – having large “artificial black surfaces” or ABSs that warm the air above them.
Here we consider the proposals and look at other ways in which people have tried to bring about changes to promote rainfall or combat climate change.
Artificial black surfaces
In a new study in Earth System Dynamics, researchers analysed how large ABSs could increase rainfall over the UAE.
Using one of Europe’s most powerful supercomputers to model the processes, they found that 10km-wide ABSs had “very little impact” on rainfall, but those that were about 20km wide were effective.
They heat the air above them, which rises, expands and cools, causing cloud and rain formation.
Dr Oliver Branch of Hohenheim University in Stuttgart, Germany, the first author of the study, said that portable black panels, black mesh or solar panels could be used.
“In the UAE there’s a sea breeze around lunchtime. These surfaces would interact and increase humidity to create clouds. This was very clear in our publication,” he said.
“It doesn’t work everywhere; it depends on the prevailing climate.”
Dr Branch has analysed plantations of jojoba in Israel that are around 2km wide and found that these, by absorbing sunlight, also cause localised heating. If large enough, these plantations are also thought likely to promote rainfall.
The researchers have calculated that, because of the climate conditions, ABSs might be effective at generating clouds and increasing rainfall at locations including Oman, Namibia, Mexico, the south-western United States and parts of Western Australia.
If ABSs were installed at a large scale, some water would probably fall over the structures themselves, while there would also be rainfall increases on their lee or downwind side.
“In the UAE it would be hard to collect [the rain], but it drains into the groundwater and would recharge the groundwater,” Dr Branch said.
“The aquifers are slowly going down because they’re over-extracting the water. This needs to be replenished and this is a possible way of doing it.”
Direct air capture
As CO2 levels in the atmosphere continue to climb and cause the planet to heat up, one proposed solution is removing the gas from the air and storing it.
If rolled out on a large scale, this could help the world achieve “negative emissions”, in which carbon dioxide levels actually fall.
Many analysts say this must be achieved because, given current trends, the world is set to significantly overshoot its aim of limiting the global average temperature increase to 1.5°C above pre-industrial levels.
As much as 10 gigatonnes of CO2 will need to be removed per year by the middle of the century, according to estimates.
Such efforts to alter the global climate are an example of geoengineering.
One direct air capture approach, developed by British company Cambridge Carbon Capture, is to mineralise the CO2 by bubbling air through a slurry that contains magnesium oxide (MgO).
This produces produce magnesium carbonate (MgCO3) and when the water is evaporated, a dry white solid remains that can be used to produce bricks for construction.
Other companies have developed methods in which the CO2 is injected deep underground, the aim being that it would remain there for thousands of years.
Climeworks, one operator, has a plant in Iceland called Orca that became operational in 2021 and is described as the world’s first large-scale CO2-removal facility.
It is able to capture up to 4,000 tonnes of CO2 each year.
The CO2 is mineralised using technology developed by the company called Carbfix.
Climeworks is building a bigger plant, Mammoth, with an annual capacity of 36,000 tonnes of CO2.
Reflecting the sun’s rays
Blasting out sulphur dioxide (SO2) high up in the atmosphere could reflect back sunlight and cool the world’s climate.
Such solar radiation management was first proposed more than three decades ago and remains an active area of research, although some are opposed to it because they feel the effects are unpredictable.
Dr Peter Irvine, lecturer in climate change and solar geoengineering at University College London, is interested in sending up SO2 as a pressurised gas. Once released, it would form particles to reduce sunlight penetration.
To be effective at a global scale, Dr Irvine said the gas would have to be released in the stratosphere (the atmospheric layer above the lowest level, the troposphere).
Further down, in the troposphere, the SO2 would get caught up in rainclouds, he said, and its effects would be less durable.
“At least to do this at a global scale you need to get up to 60,000 feet [around 18km] – twice the altitude of normal jets. That means you need new jets. They don’t exist but they could be built,” he said.
He said the technique might work in the Arctic with conventional aircraft, because in this region the stratosphere is lower. Some proposals involve balloons instead of aeroplanes.
The Centre for Climate Repair at the University of Cambridge has a proposal to refreeze the Arctic by deploying hundreds or thousands of ships to send a mist of seawater into the air to deflect sunlight.
This could protect or strengthen Arctic sea ice and the vast ice sheet that covers Greenland, which locks up water that, if released, would cause sea levels to rise.
Dr Irvine said that much research has been focused on clouds called marine stratocumulus decks, which naturally form off places such as California and Chile, but he said there was a chance that the technique could work in the Arctic too.
Cloud seeding
As many as 50 countries are thought to have carried out cloud seeding operations and the method dates back more than half a century.
The UAE has been conducting operations for around half that time and in a single year the National Centre of Meteorology, through its UAE Rain Enhancement Programme, may run hundreds of missions.
The technique involves sending up an aircraft that fires flares that release particles of silver iodide (in colder parts of the world) or sodium chloride (in warmer areas).
These particles act as condensation nuclei around which ice crystals may form. These then fall as precipitation, either rain or snow.
In clear skies the technique can increase rainfall produced by a cloud by around 35 per cent, while in hazier conditions the increase is between 10 per cent and 15 per cent.
Cloud seeding’s overall effectiveness at increasing rainfall in an area has been questioned and the results depend on the time and place at which the work is carried out.
Deploying environmental modification technologies as a weapon of war is banned under a UN convention that came into force in 1978 and has been signed by 48 states, although not all of these have ratified it.
The Convention on the Prohibition of Military or any other Hostile use of Environmental Modification Techniques, or Enmod treaty, bans the military or hostile use of environment modification technologies when they have “widespread, long-lasting or severe effects as the means of destruction, damage or injury”.
This means that actions that would have effects lasting months or a season are prohibited.
The convention allows scientific collaboration between countries on environmental modification for peaceful means.
