Does cyclone modification geoengineering make sense?

Geoengineering hurricanes and cyclones?Is what a group of engineering policy researchers and atmospheric scientists from Carnegie Mellon and MIT asked themselves. Considering increasing hurricane damage around the Gulf of Mexico – and technological options – they get to a ‘maybe’.

Atlantic hurricanes develop out of tropical cyclones, strong depressions that usually form off the coast of West Africa (from African thunderstorms in or close to the ITCZ), and are then transported westwards by the Atlantic trade winds. These trade winds also help to assemble a lot of tropical warm water in the Caribbean Sea and the Gulf of Mexico. The tropical cyclones that bend northwards, move across this warm water, that adds more vertical convection power and moisture to the weather system – that can then turn into a closed circulation hurricane.

The warmer the water, the more energy gets sucked in the air and the faster a tropical cyclone develops into a hurricane and the more powerful this hurricane can grow – other complex meteorological factors left aside.

Now it is indeed hard to stop a full-blown hurricane, but you can perhaps starve a tropical cyclone by trying to cut off part of its energy supply. The researchers, who last month published their findings in Environmental Science & Technology, have investigated the possibility of cooling a cyclone path, with wind-wave pumps.

Making use of wave energy such floating pump systems well up cool, deep ocean water. For this study (theoretical) pumps, placed 333m apart and pumping cold water from a depth of 300m are considered for creating the sea surface temperature (SST) reduction.

Using a modern tropical cyclone model (simulating the famous hurricane Andrew of 1992, which was forecast to make landfall around Miami) they find cyclone modification is indeed theoretically capable of reducing hurricane development and storm damage. The researchers estimate deploying the pumps in an area to protect Miami would cost 0.9 to 1.5 billion dollars per year and should decrease SST by 1-1.5 degrees Celsius. Nice thing about the idea is the pumps start working much harder as the storm approaches and wave heights increase.

To get to policy options the researchers do another interesting thing. They let their cyclone model compare wind damage with either cyclone management or with hardening strategies to protect buildings – and find “if practically feasible and properly implemented, modification could reduce net losses from an intense storm more than hardening structures” [or to translate this to policy speech, do it equally good at a lower financial cost].

Cost comparison of geoengineering tropical cyclones
Cost comparison of storm damage, comparing inaction, various intensities of geoengineering, and improving urban structures in cyclone and hurricane vulnerable areas. [From Environmental Science & Technology publication.]

It is not the first time geoengineering thinking has been stretched to target the nastier bits of our climate: we wrote about modifying El Niños and La Niñas in January. And although ‘weather improvement’ is not quite the same thing as ‘solving’ climate change – here we get to a big parallel with the more globally ambitious forms of geoengineering, especially the SRM techniques that seek to create a compensating cooling effect on a planetary scale: they are (likely) much cheaper than emissions reductions.

As these SRM techniques are also largely unproven, require a mostly peaceful world to be deployed in, require the bending of judiciary systems, may backfire climatologically and do ‘nothing’ [considering ocean temperature feedbacks they actually do do something] to abate ocean acidification – the simple notion that it is cheap [again, policy thinking] makes geoengineering so dangerous, possibly undermining cooperation behind the world’s mitigation attempts, under the UNFCCC, the hard route that we need to go anyway* [as CDR geoengineering lacks the potential to get carbon concentrations back to safe levels, also for marine life – and isn’t much cheaper/is costlier anyway].

The researchers understand you may also have to highlight such dilemmas in the case of cyclone management, so they conclude: “However, hardening [of buildings] provides ‘fail safe’ protection for average storms that might not be achieved if the only option were [cyclone] modification.”

So perhaps add a little concrete to your new Florida bungalow. If only to prevent you from feeling really silly once the wind-wave pumps fail – or the weathermen are mistaken and perhaps send pumps away to cool the wrong trajectory.

[*) It also remains important to note we don’t just need emissions reductions anyway, we’ll also be needing geoengineering anyway, judging by various IEA full implementation mitigation potentials (including nuclear and CCS). Many don’t get this – but it goes for both the temperature targets of ≤2 degrees (UN, G8, G21) and ≤1.5 degrees (wiser people) and the internationally accepted maximum GHG concentration level of 450 ppm – and for the CO2 stabilisation concentration level of 350 ppm (Hansen and many other climate scientists): if we know ‘2’ is the right answer, we’re not that clever when we fail to comprehend 1+1 is the logical route to getting there.]

© Rolf Schuttenhelm |

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