THE FIRST OF MANY MORE TO COME?
The tragedy of five people dead in the Cape Town storm is a terrible thing. The worst part of it is that these deaths were preventable. Climate change scientists have for years been warning of extreme weather arising from global warming. With this blog I thought I should explain why this is so, making the links clear for everybody to understand. We cannot lend these deaths meaning unless we do our utmost best to ensure it never happens again. This requires an understanding of the dynamics at play and the reasons behind the increased occurrence of extreme weather.
A good starting point is to understand that, although the planet has become on average one degree Celsius hotter, the planet is not warming evenly or at the same pace everywhere. Africa, for instance, is warming up faster than the global average. This leads to instability in the world’s weather patterns.
The scientific basis for this claim was established in 2013 when it was shown that because of the increase in temperature around the equator, the winds which together constitute the weather pattern known as the jetstreams, were moving gradually away from the equator. The jetstreams are instrumental in regulating the climate, bringing monsoons to the east and rain the west. What has happened is that jet stream oscillations are increasing
. This means that the wave patterns of air they sketch back and forth across the equator have become more extreme. The jet streams are slowing, and increasing oscillation is moving extreme weather north and south. The typhoons, hurricanes and cyclones which used to hit the tropics are now hitting further north and south as the extreme end of jet stream oscillation moves.[i] It has been concluded that “Man-made climate change repeatedly disturbs the patterns of atmospheric flow…through a subtle resonance mechanism”[ii]
But the problem is not just an increase in frequency of superstorms. It is also that they hitting new areas of the planet. The tropics which are used to strong winds have indigenous vegetation and freshwater drainage systems which help them recover quickly. The areas which are receiving these storms now are not likely to do so well under the impact. How long do you think before Cape Town recovers? What else could we have done with the money which will now be spent on rebuilding what was there?
The second factor which affects the frequency of extreme weather is that wind is essentially a consequence of differentials in air temperature. In Cape Town, for instance, the south easter arises because the air in the hot uplands is warmer than the air at the coast. Now, if the Karoo is heating up faster than the coastal areas the south easter will become worse. This accounts for the increase in gale force winds we have had lately. This effect can be seen all over Africa as temperature differentials between land and sea increase. [iii]
This new research also explains how we now have floods and droughts at the same time. In the case of Johannesburg, of course, it was easy to understand that although it rained, it rained in Johannesburg and not in the catchment areas which feed the Vaaal and the !Gariep. So Johannesburg had drought, then floods but no potable water at the same time. But the same thing can happen to Cape Town, although it has rained on our one and only watershed. For every 1° C increase in temperature, there is a 7% increase in the amount of humidity that the atmosphere can hold. This leads to more evaporation, heavier rain and worse storms. But it also leads to more evaporation and water being sucked out of the top layers of soil. This leads to drought.[iv] Because we have denuded the land of trees and shrubs, while we have ploughed and poisoned all the humus out of the soil, there is nothing to capture the water as it falls. It erodes the bare soil and runs off hard surfaces. This means that when the next drought hits the landscape has no resilience. In essence the lack of water is systemic, it is linked to the way we farm and build our cities. Climate change is an additional spanner in the works which highlights the weaknesses in our systems of living.
The death of three people in the Knysna fires is incredibly sad. But it is not enough to express sympathy. We need to understand the reasons for these fires so that we can know how to stop them from happening. It is the increase in high winds which also accounts for the rising intensity of forest and settlement fires. Warming temperatures mean the rate of evaporation increases, that is, soil and plants are drier than they used to be. Add a high wind in this context and it will make fires go out of control. There is indeed very little that all the technology of humans can do until the wind dies down. As climate change gets worse, we must expect more high winds on drier land.
In conclusion we need to see these tragic deaths in context. It has been estimated that already in the last decade over half a million deaths can be attributed to climate change. [v]So, all things considered, should the City of Cape Town and the Western Cape Province really be investing lots of money in supporting a huge natural gas plant in Saldanha Bay? [vi] Is an expansion of the natural gas system either safe or desirable, given that we need to be reducing carbon emissions and checking every new development in the light of the risks imposed by increases in extreme weather? But what is most disturbing to me has been the relative absence of critical voices from Cape Town civil society. As we mop up after the storm, we need to ask ourselves if we have done enough to stop climate change where we can, and deal with the effects of it were we cannot. We need to act now because the one thing we do know is that this storm will be the first of many.
[i] . Petoukhov, V., Rahmstorf, S., Petri, S., Schellnhuber, H. J. (2013): Quasi-Resonant Amplification Of Planetary Waves And Recent Northern Hemisphere Weather Extremes. Proceedings of the National Academy of Sciences (Early Edition) [doi:10.1073/pnas.1222000110]
Jisk J Attema, , Jessica M Loriaux1, and Geert Lenderink Extreme precipitation response to climate perturbations in an atmospheric mesoscale model http://iopscience.iop.org/1748-9326/9/1/014003/pdf/1748-9326_9_1_014003.pdf