Tropical Storm Ana in January, Tropical Cyclone Batsirai in February, then Dumako, Emnati and Gombe in quick succession: three cyclones and two ‘tropical storms’ in six weeks hitting the coasts of south-east Africa.
Then Cyclone Idai hits Mozambique in late March, killing more than 750 people. Three weeks later Subtropical Depression Issa batters South Africa’s east coast, killing 450 people in the greater Durban area. Millions made homeless in Tanzania, Mozambique and South Africa in three months.
Yet just five years ago there were only one or two of these storms a year in the region. Fifteen years ago, the average was not even one per year. “It is telling us that climate change is serious, it is here,” said South Africa’s President Cyril Ramaphosa. Well spotted, sir. Bit late, though.
Cyclones in the Indian Ocean, typhoons in the western Pacific, hurricanes in the Caribbean – it’s all the same beast, just different names. Likewise ‘tropical storms’ and ‘subtropical depressions’; same beast again but with a lower wind speed. Still enough to tear the roof off your shack, though, and maybe drown you if you live up on the side of a ravine.
Why is anybody surprised? Rising global temperature warms the surface of the ocean. When the sea surface is above 26.5 degrees Celsius (80°F), it has enough energy to fuel hurricanes/cyclones/typhoons. The western Indian Ocean is now above that temperature between January and April, so of course it’s spawning cyclones.
But it may be possible to weaken or even stop these storms – and maybe southern Africa is the place to try it, because people haven’t got used to a constant procession of violent tropical storms yet. They might even be open to the idea that they don’t have to get used to it.
Last year I interviewed a retired professor of engineering called Stephen Salter who began working on a project for cooling the climate several decades ago in collaboration with Prof. John Latham, a renowned climate scientist. Latham died last year, but the project is ready to start building prototypes, and it really might work.
The idea is to build a fleet of unmanned, wind-powered, satellite-guided vessels that
position themselves under the low, thin clouds that are very common in tropical oceans – ‘marine stratocumulus clouds’ – and spray a fine mist of water that thickens them up so that they reflect more sunlight.
Reflect more sunlight and you cool the whole planet – but you particularly cool the surface of the ocean under those clouds.
The big ‘named’ tropical storms form in well-defined areas of the Atlantic, Indian and Pacific Oceans that are not unmanageably large for mobile fleets of spray-vessels. Just drop the sea-surface temperature by one degree or less, and most of the storms that are forming will never get big enough to earn a name.
It’s worth a try, and maybe southern Africa is new enough to this kind of weather to believe that it could be stopped. South Africa would have to take the lead, because that’s where most of the money and the scientific and engineering skills are, but it matters to the whole east coast of the continent.
In fact, it matters to the whole world. We will need technologies to hold the global temperature down while we work to eliminate our greenhouse gas emissions, and this would be a cheap, low-impact way to do it.
It would also be a project of global scientific and political importance led by Africans, which is something that is long overdue.