As maximum temperatures soared to 39°C in South Africa’s capital city, Pretoria, during the second week of November, residents were asking: why is it so unbearably hot this year? And why have there been successive heat waves?
It was the second or third heat wave to hit the country’s Gauteng province in the early summer. But it was not isolated to one province. Other parts of South Africa are also experiencing anomalous weather.
There was a heat wave in coastal Cape Town, unusual spring thunderstorms and strange cloud formations in the Western Cape province along with the well-publicised drought in the summer rainfall region all across the country.
The question is why? There are three probable culprits: regular climate dynamics, a phenomenon known as El Niño, and global warming. Which of these is the dominant cause is a matter of scientific climate research, but there are some conclusions we can draw.
Regular climate dynamics and global warming
Inter-annual and decadal climate variability and extreme weather events are natural phenomena. This means that South Africa from time to time experiences years that are unusually wet and cool compared to the long-term average.
At other times the country experiences relatively very dry and warm periods. This type of variability is part of the Earth’s natural climate dynamics and is partially caused by oscillations and complex configurations of global and regional climate systems working in concert to produce our weather.
Climate change is different from inter-annual climate variability. Climate change is a result of global warming which is caused by human activities that have resulted in the emission of various pollutants, principally carbon dioxide. This has altered Earth system dynamics in a way that affects the climate system, ultimately causing trends and changes to climate and weather systems.
Climate models project that, given the current rate of carbon dioxide emissions into the atmosphere, and some unique features of South Africa’s climate system, like our location in the subtropics and the important role that high pressure systems play in controlling the system, temperatures in southern Africa are likely to increase by at least 1.5 times the global average rate of temperature increase.
The warmer weather South Africa is experiencing now is not solely attributable to climate change, but is likely to be a touch of what we may experience more often in the future. This is based on the evidence from climate scientists running powerful models to compute the climate projections of the future.
Of more immediate concern is the 2015 El Niño. This is a phenomenon that occurs every two to seven years and appears when large parts of the eastern and central Pacific Ocean are experiencing above normal sea-surface temperatures. One of the strongest El Niño events ever observed has settled over the Pacific.
In South Africa, El Niño is usually associated with below normal rainfall and above normal temperatures during the mid-summer period of December to February. The presence of the strong El Niño event in combination with global warming means that it is no coincidence that 2015 is on track to be the warmest year ever recorded by humans in the 150-year record of reliable observations.
Nine of the 10 warmest years on record have been observed during the last ten years. The current spell of heatwaves and record-high temperatures are a combination of global temperature extremes due to El Niño in combination with the effects of systematic greenhouse gas warming.
The exact mechanisms and linkages across the global climate system are the subject of ongoing research. For example, will El Niño occur more frequently, more intensely and for longer duration with its impacts on global weather in the future?
South Africa was in an existing state of drought even before the 2015 El Niño started to have its impact. This was due to the previous two rainfall seasons being associated with below-normal rainfall over much of the country. There was a weak El Niño in 2014. The situation is therefore more serious this summer with El Nino likely to cause a third season with below normal rainfall and above normal temperatures.
The effects on human health
High temperatures, especially over long stretches of hot days, have a negative impact on human health, animals, agriculture and the natural environment.
Adverse human health symptoms and effects – such as fatigue, fainting, headaches, heat cramps and heatstroke – may become more common with higher temperatures. The impact on infectious diseases, such as diarrhoea, is also predicted to increase with increased temperature.
People with pre-existing diseases, such as HIV-AIDS and TB, children and the elderly, are especially vulnerable. People with suppressed immune systems, or developing immune systems in the case of children, may find it difficult to cope with warm temperatures.
What is to be done
There are two basic options – adapt and mitigate. Adaptation involves engineering ways to cope with our extreme weather and changes to climate. An example would be building more suitable housing or planting drought resistant crops. The other is to try to mitigate the impacts of climate change by reducing its manifestation.
The 2015 Conference of the Parties, COP21, to be held in Paris, France in November and December 2015 under the auspices of the United Nations Framework Convention on Climate Change, will be a crucial meeting towards significant reductions in greenhouse gas emissions during the 21st century.
The correct strategy is the subject of complex debates especially for developing countries. But as a global community there can be no doubt that this is a critical issue. It will become a looming international crisis and world economies and populations will feel the pinch.
This week, the World Health Organisation called all health professionals to action in the fight against climate change. The health community is being urged to advocate for a healthier and more sustainable future. Other sectors of society and communities have important roles to play in realising this goal and finding creative ways to mitigate and adapt.
Caradee Yael Wright, Specialist Scientist (Public Health), South African Medical Research Council; Francois Engelbrecht, Research Group Leader, Climate Studies and Modelling and Environmental Health, Council for Scientific and Industrial Research, and Neville Sweijd, Acting Director and Operations Manager at ACCESS, Applied Centre for Climate and Earth Systems Science