The Cape of Storms, and climate change

[Nat Quinn]

No less than 828mm of rain fell on East London in a few days. Twelve people were killed in the floods. Many houses were destroyed. The surging waters swept furniture and jetties into the sea. The floods were so violent that people believed that the dam on the Buffalo River had burst. (It hadn’t). The huge Union Castle Liner, the Southampton Castle, was so rocked in the docks that she knocked over a giant crane. Insurers had to pay out millions of rands. The rain began on Monday, 24 August 1970 and continued until the next Sunday.

In Laingsburg in the Western Cape, 425mm fell in two days. The floods killed over 100 people; 72 bodies were never found. Even survivors were swept as far as 21km away. 184 houses were destroyed. If you go to Laingsburg you can see a marker showing the high level of water in the flood. It is unbelievably high. The rain fell on 25 and 26 January 1981.

Last week, storms with heavy rain and fierce winds swept the Western Cape. It was reported that in a 24-hour period from Sunday 24 September up to 170mm fell on the Overberg, 133mm on the Winelands and 92mm on the Cape Town docks. Floods caused havoc over a wide region. Houses were flooded, families were displaced, roads and bridges were so badly damaged they could not be used. People in Pringle Bay and Betty’s Bay were marooned because Clarence Drive (the coast road from Rooi Els to Gordon’s Bay) was closed because of mudslides and the bridge over the Palmiet River just before Kleinmond was too badly damaged to be used by cars. So was the N2 bridge at Botrivier. Eleven deaths have been reported so far, although I’m afraid more might follow. (Four children were electrocuted when an illegal connection was flooded.)

In 1488 the Portuguese navigator, Bartholomeu Dias rounded the southernmost tip of Africa and anchored at what is now Mossel Bay. He was probably the first man to do so although there are some not very convincing theories that Phoenicians might have done so in ancient times. He realised that only open sea stood between him and India, the destination and purpose of his voyage, fulfilling the centuries-old dream of commercial Europe of finding a sea route to India. But his crew refused to carry on and he was forced to return to Portugal. The main reason they refused was the damned awful weather they had encountered round what is now the Cape. He named it The Cape of Storms (Cabo das Tormentas), an accurate description at the time. The 15^th Century had far worse weather extremes than now, far worse storms and floods. However, his king, King John, choosing diplomacy over fact, renamed it The Cape of Good Hope, a name that the Western Cape tourist board still uses.

Idiotic theories

Of course, this month’s storms in the Western Cape are blamed on – sigh! – climate change, by which they mean man-made climate change. Idiotic theories try to explain why this is so. One says that climate change (by which they mean rising CO2) is making the Earth warmer, so increasing evaporation, so putting more water into the atmosphere, resulting in more rain. Another says that climate change is increasing the total energy in the weather system (land, sea and air), which worsens extreme weather events. Both show complete ignorance of thermodynamics and history. The same people that say rising temperatures will cause more floods also say that they will cause more droughts. They said this of the drought in Cape Town in 2017. I even heard somebody claim it was a one-in-four-hundred-year drought. (Actually, there had been worse in the 20^th Century.)

First, CO2 over 150ppm has never been seen to cause warming in the Earth’s history. A thousand years ago it was warmer than now while CO2 was lower than now, and ditto for previous warm periods. Second, the warmer the climate, the fewer and less intense the weather extremes. In the worst cold of the last 10,000 years, during the Little Ice Age (LIA), from about 1300 to 1850 AD, weather extremes were far worse than now, with terrible storms, floods and droughts, such as we have never experienced in modern times, devastating countries and populations, causing famines and wars. That is why Bartholomeu Dias encountered such horrible weather at the Cape. Climate change, which is entirely natural, has very little effect at the equator but a considerable effect at the poles. The higher the latitude, the more climate changes.  Since the equator hardly varies in time but the poles vary a lot, the colder it gets, the bigger the difference between temperatures at the equator and those at the poles. This is what causes more extreme weather.

Winds, storms and cyclones are caused not by total energy but by energy available for work. (Cyclones, typhoons and hurricanes are different names for the same thing.) They are heat engines, which depend on temperature differences, like coal, gas and nuclear power stations, and like the engine in your motorcar. Cyclones are caused by the difference in the temperatures of moist air at sea level and cold air above it. If everywhere on land, sea and air was at exactly at 20 degrees C or exactly 40 degrees C, there would be no cyclones, no rain, in fact very little weather at all. (Thank goodness, this is impossible.) Temperature and pressure are inter-related. The bigger the difference between the temperatures at the equator and the poles, the bigger the pressure difference, and the more air you get moving from high pressure to low pressure, causing stronger wind and more storms. The Mediaeval Warm Period (MWP), about 900 to 1200 AD, was warmer than now, and had pleasant, healthy, equable weather and was a golden age for European agriculture. The Little Ice Age was colder than now with terrible weather and crop failures and famines. During the last Ice Age, the weather in Europe, those parts not covered in snow, was unspeakably awful and extreme. It is a wonder that our ancestors there survived them.

Extremely complicated

The bad weather in the Western Cape has nothing to do with rising CO2, any more than the East London and Laingsburg floods had anything to do with lower CO2 levels then. The Earth’s weather system is extremely complicated, beyond our complete understanding now and perhaps forever. But we do understand certain basic principles and our weather forecasting is improving. I seem to remember that the weathermen were caught by surprise by the 1970 floods in East London. This time in Cape Town, they all gave us good and accurate warning. Extreme weather events might vary in frequency and intensity, but they are always going to happen.

Where I live, near Fish Hoek, we suffered minimally in the storms. Fish Hoek is a dry place with low rainfall. Over the weekend of storms, I picked up a rise on my rain gauge but not a dramatic one (I neglected to read the level before the storm, I’m afraid). The winds were strong all right, but Fish Hoek people are used to strong winds and these were not exceptional. I still managed to ride my bicycle in them. None of the many trees in my garden were damaged. But there was devastation and lost lives in places not far away, where trees were blown over and where I should not have been able to ride my bicycle.

I first arrived in Fish Hoek in 1953 as a toddler, and have lived here on and off, with long spells in England and other parts of South Africa. Childhood memories are notoriously unreliable, but some are still strong in my mind. I loved the Fish Hoek sand dunes and spent a lot of my childhood in them in the late 1950s and early 1960s. There was a little vlei at the end of the dunes. I looked at it last week, after the rains. It seemed to me much smaller than after rains in the past (although it was heaving with tadpoles). However, I know sand movements here are very complicated. The dunes themselves have shrunk dramatically, partly because of urban creep but mainly because plants are growing profusely where none were before. The white dunes are disappearing under green vegetation. This time I think mankind is to blame. I’m sure rising CO2 is promoting plant growth here as elsewhere on Earth, especially in regions with low rainfall, notably the Sahel.

Killer waves

Recently huge waves have lashed coasts around the Western Cape, causing damage to houses and restaurants. Again, there is nothing unusual about this. Dias almost certainly experienced worse. But the seas off the south coast of South Africa do have a unique danger, a strange and fearful danger: killer waves.

I can’t think of any recent cases, but a few decades ago, huge ships, including oil tankers, would limp into the Cape Town docks, with their fronts missing, as if they had been hit by a colossal axe. Their captains would tell this story. As they were sailing around the Cape, they would suddenly see a huge pit in the water ahead of them. The ship would fall forward into the pit, and then a mountain of water just in front of the pit would smash into the ship, sometimes breaking it in two.

There is some peculiar combination of different wave sets, some coming from the Antarctic, some from elsewhere, meeting each other. Sometimes meeting waves cancel each other, sometimes they reinforce each other. In certain circumstances two sets of huge waves would meet each other off our coast and amplify each other, joining together to form a wave of mountainous size and terrifying strength. Dias’s ship, a caravel, was tiny, about 15 metres long. It might have been better against killer waves than a modern oil tanker because it would probably have bobbed up and down in the wave like a cork – but if the wave had broken over it, that would have been that.

The Western Cape can expect more storms, more floods and strong winds, because they have always happened and will always happen. Our weather forecasting has improved, which is a great advantage. If we know when they’re coming, we can prepare for them better. It seems to me that the Western Cape government has done a fairly decent job of rescue and repair. Every road that we plan and build now, every bridge, every storm water drain and culvert, and every building in vulnerable zones, should require an optimal amount of money to be spent in designing against weather extremes. We shouldn’t overdo it.

It would be as silly to design against a one-in-a-thousand-year storm as it would be to cover every school with a reinforced concrete dome to protect the children against crashing aeroplanes. Take reasonable, cost-effective precautions. That’s the best we can do, and it’s a lot.

 

source:The Cape of Storms, and climate change – Daily Friend

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