Cape Town - Contrary to what we’ve all been thinking, Cape Town has had a “super wet” summer, according to UCT scientist Peter Johnston.
And that is the problem, in a sense. It is a problem of misappreciating an existential condition of life in the Western Cape; nature can be counted on to be unerringly capricious in the short term, but, in the long term, only more taxing.
If season-to-season weather can be almost mysteriously unpredictable, climate displays a grim certitude.
The combined effect, as Johnston put it, was that “it’s not just about what we are going to wear”.
“We can make ourselves comfortable, isolate ourselves from what’s going on outside and act as if we are independent of the weather, but our food and water, our most basic needs, are weather-dependent.”
There was no getting away from the impact of the weather, and the Western Cape’s current water crisis had forcibly brought this truth home.
The crisis was not, however, a function of low summer rainfall - there has been more rain than the average this summer - but of lower than average rainfall in the rain season.
“The long-term averages for Cape Town (measured at the airport) are only 17mm, 13mm and 8mm for December, January and February respectively. So far this summer some areas received well above those averages, but because we had a drought in our winter rain season, we are still desperately short of water in the dams.”
It could seem, then, that soaking rains from May onwards would be the Cape’s saving grace - but this way of thinking, Johnston argued, posed the greater risk of overlooking that existential truth about our region, which was that “it really is a dry place”.
Coupled with that, the population was growing, more people were moving into homes with taps and lavatories, the infrastructure to deliver water was ageing and leakier than it should be, and new readily available sources of water were limited.
Thus, he urged, the conservation-mindedness of these past worrying weeks should become conventional year-round behaviour, rather than only an emergency response to the falling levels of dams.
Making sense of it all calls on two strands of analysis: climate variability - what the weather is likely to do in the next weeks or months - and climate change, the likely longer-term changes and impacts.
The scale of vulnerability, and the adaptation required to minimise it, may differ in assessing what the weather will be doing next summer, or what is likely in the next six to eight decades.
But Johnston said a “suite” of models which, though containing a measure of uncertainty about whether the Cape would be wetter or drier by the end of the century, all agreed that it would be hotter.
Taken together with the growing demand for water and the limited scope for new sources, good winter rains and fuller dams ought not to be as comforting as they may seem in the short term.
Johnston grew up “loving weather”.
“My father, Tom, was a yachtsman, and I did a lot of sailing, too, which meant taking a close interest in the weather. So I was always interested in the topic - and decided early on that I wanted to teach geography.”
In a 15-year teaching career he ended up teaching more science than geography, and rounded off his decade-and-a-half in school education as a principal.
But he returned to his first love when he joined UCT as project manager in the Climate System Analysis Group in the department of environmental and geographic science.
He works extensively with farmers (his PhD was on seasonal forecasting in the maize sector), private companies, international agencies, national and provincial governments and municipalities, sharing weather and climate data, forecasts and analyses of risk.
In addition, every Monday and Friday he spends an hour or so crafting a mail to an audience that began as just a few friends and now numbers some 1200 people.
Most have never met him and know him chiefly by his signature “Weatherman” tag and the breezy style and occasional humorous asides of his weather “reports”.
One this week began: “So a collection of droplets conspired to coalesce and condense into 4.1mm of rainfall overnight. And, as with all conspiracies, there was considerable natural obfuscation in the aftermath this morning... that would be the fog, Doris!”
He said this week: “I try to explain to people what’s happening in a non-serious way. It’s teaching people things. And because I have access to some data that others don’t have access to, it’s fun sharing that.”
At the heart of the enterprise, however, was a brutal realism about the weather; it was visited upon us with a degree of uncertainty, and a scale of impact, that could be unnerving.
In framing his PhD, Johnston drew in part on the biblical aphorism - from the book of Matthew - that God “sendeth rain on the just and on the unjust”.
Nothing, it suggests, guarantees relief from the sky. Rain is neither deserved nor undeserved, and nor can it be predicted with anything like the certainty that day follows night.
And this much was confirmed by the records, and the models built on the data.
“Climate variability means that the weather changes from year to year.
"So for the past 15 years we have been building and using a climate seasonal forecasting model to predict weather three months in advance.
"It is not very good, or ‘skilful’, but it gives some insight into what might happen.”
The key “signal” of weather patterns was ocean temperature, the El Niño or La Niña phenomena in the Pacific Ocean, and their correlation - or “teleconnection” - to conditions across the globe.
Even then, however, there was some uncertainty.
“Sixty percent of the time, if there’s an El Niño condition, central and southern Africa get dry weather or drought.
"It happened last year, it happened in the last El Niño, and in most of them.
"But it does not always happen. It also does not affect the Western Cape - yet we have had a drought.”
Predictions, then, had to take account of these anomalies.
When it came to water, and the impact of drought and climate change, Johnston said, “that’s where we have to catch a wake-up”.
“We know from climate scenarios - a number of models that are run in different starting conditions - that there is uncertainty about rainfall. Not all the models agree. Most models suggest that in the long term, the Western Cape will be drier, but some say it will be wetter.
“But all the models agree on temperature; we are going to get up to 2ºC to 4ºC warmer by the end of the century.
"There is no uncertainty that we are getting hotter - we have seen in the trend analysis that the southern half of Africa is likely to get hotter than the world average.”
Even if the region became wetter, higher temperatures would mean greater demand for water.
“Cape Town is under threat from three main things: the population is increasing and getting more infrastructure, with more people moving into houses with taps and using more water; the likelihood of increased temperatures means more water will evaporate and people will want to use more; and, like every city in the world, our infrastructure is getting old, is leaking more, and is taking more energy and effort to maintain.”
The city council had made concerted efforts to find and repair leaks and upgrade infrastructure.
“There are opportunities in supply management - finding more places to get water, such as the aquifer (underground water) or increasing dam walls. But the most important response is on the demand side - reducing the water demand - and that’s where everyone has an important role.
“At the moment we are all aware of water use. Never before did people worry about leaving the sprinkler on, or leaving the hose running while washing the car. People are more aware. But what about when the dams are full? Will we revert to our old behaviour, or keep at it?”
A water-short future, Johnston warned, “is something we cannot wish away”.