Heatwaves in SA are occurring more frequently and are expected to last longer- report

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Published Jul 18, 2020


Heatwaves in much of South Africa are occurring more frequently and are expected to last longer - over two weeks in rare circumstances - and to become more intense.

A new scientific paper, Heatwaves in the Future Warmer Climate of South Africa, describes how weather and climate extremes have become more frequent because of climate change, resulting in negative environmental and socio-economic impacts in many regions of the world. 

“The high vulnerability of South African society to the impacts of warm extreme temperatures makes the study of the effect of climate change on future heatwaves necessary,” writes a team from the SA Weather Service, University of Venda, North West University and Wits University, in their study, published in the journal, Atmosphere, on July 3.

While heatwaves have been extensively studied in continental Europe and Australia, they “have not received rigorous research attention in SA, even though they have devastating impacts on society and livelihoods”.

Increases in heatwave frequency and duration may have significant impacts on human health, economic activities and livelihoods in vulnerable communities. The researchers investigated the projected effect of climate change on the future of South Africa with a focus on heatwaves using an ensemble of regional climate model downscalings from the Conformal Cubic Atmospheric Model for 2010-2039, 2040-2069, and 2070-2099 using 1983-2012 as the historical baseline.

Simulations were performed under the Representative Concentration Pathway (RCP) 4.5 (moderate greenhouse gas [GHG] concentration) and 8.5 (high GHG concentration) greenhouse gas emission scenarios.

“We found that the 30-year period average maximum temperatures may rise by up to 6°C across much of the interior of South Africa by 2070-2099 with respect to 1983-2012 under a high GHG concentration.”

This increases the likelihood of having intense and frequent heatwave occurrences. The increasing intensity is highly indicated under the RCP 8.5 than 4.5, say the researchers.

“Heatwaves are relatively unusual in the present-day climate but are expected to occur more frequently in the future warmer climate when using both RCP 4.5 and RCP 8.5 emission scenarios, particularly during the far future period, 2070-2099, reaching an over 50% increase in both summer and winter.”

Heatwaves are also expected to last longer, particularly across the interior, and become more intense, which the authors say is in agreement with earlier findings about the nature of heatwaves in the 21st century. The north-western parts of the country are expected to have the most drastic increase in heatwave occurrences.

During the 2070-2099, period an average increase of two heatwaves per three-month season per year is expected, “which is similar to earlier findings that a median increase of 2.5 events per degree of global warming is expected across southern Africa in the 21st century”.

Under a high GHG concentration, short-lasting heatwaves, lasting three to four days, along the coastal areas are expected to increase in frequency in the future climate.

However, the coasts will continue to experience heatwaves of relatively shorter duration compared with interior regions. Winter heatwaves are expected to extend to the eastern interior and to also increase in intensity reaching over 47°C/30-year.

Extreme events not reported

Climate change is causing extreme heat events in sub-Saharan Africa to rapidly worsen but official records suggest they are not happening, despite the region being a "literal hotspot for heatwave activity". 

Extreme weather damage databases report no significant heatwave impacts in Sub-Saharan Africa since 1900 yet the region has experienced a number of heatwaves and will be affected disproportionately by them, says a new paper published this week in Nature Climate Change. 

Addressing this reporting discrepancy is critical to address the impacts of future extreme heat in the region. The University of Oxford analysis identified a near-absence of reported heatwave events over the region in disaster databases, meaning that the impacts of heatwaves – including heat-related deaths - are not reported, putting the population at further risk. 

Extreme heatwave events can lead to economic losses, serious health impacts, and deaths in vulnerable communities. The researchers state how heatwave action plans and early warning systems are invaluable in mitigating the impacts of extreme temperatures. However, without accurate records, such work can be undermined. 

Just two heatwaves in sub-Saharan Africa have been listed in the last 120 years in the Emergency Events Database (EM-DAT), which contains the most comprehensive list of past heatwave events globally. 

By contrast, 83 European heatwaves have been listed in the last 40 years, events which resulted in more than 140 000 deaths and some $12 billion in damages.

In Europe, heat action plans are generally triggered when temperatures are predicted to be high for more than three days and usually don't last longer than a few weeks. 

By contrast, in 1992, one heatwave in sub-Saharan Africa lasted more than four months - compounding the impact of one of the worst droughts in recent history, they explain. Yet the EM-DAT contains no record.

"Both real-world observations and climate modelling show sub-Saharan Africa hotspot for heatwave activity," says study author Dr Luke Harrington, in a statement. "But these heatwaves are not being recorded in disaster databases. "It’s as if they haven’t happened, but we know they have. There is an urgent need to address this discrepancy to help regional policymakers assess and plan for the future impacts of extreme heat." 

The authors argue when reliable data is combined with local expertise the impacts of heatwaves can be predictable, and this foresight can prevent unnecessary deaths. "Improving this kind of data is vital to reducing the risks of extreme weather and climate-related events."

Barriers in sub-Saharan Africa include the sparsity of meteorological data, weaker governance frameworks and lack of institutional resources. Prof Rebecca Garland, principal researcher at the climate and air quality modelling group at the CSIR, says the Oxford findings are worrying. "In southern Africa we are already experiencing warming from climate change and this is projected to continue into the future. People's health is at risk from increasing temperatures, and it is worrisome that we don't have a sense of how large of a problem it is now. 

Without this information we can't identify who has been the most impacted and what is needed to decrease their vulnerability. Not having this information limits our ability to mitigate the health impacts now and plan for the future."  

She agrees with the research priorities noted by the Oxford researchers. "In addition, I think this also really highlights the importance of having and supporting open data, and strengthening collaborations with African scientists. There is local knowledge and expertise on these events, but that expertise and information are not making their way into global databases. 

"This is not unique to extreme events (such as heat waves), but is true for a lot of environmental data. Improving this link between local researchers and expertise and global databases is critical, and takes the involvement of many stakeholders to ensure that openly sharing environmental data is prioritised." Dr Mary Jane Bopape, chief scientist at the SA Weather Service, says local research indicates that there are a lot more heatwaves than those reported by EM-DAT.

"The number of disasters reported by EM-DAT are generally lower than those experienced on the ground because of the strict criteria followed for an event to be listed. Their requirement is that one of the following criteria be met: 1 10 or more people that die due to the event, or 2) 100 or more people affected, or 3) a declaration of a state of emergency and lastly 4) a call for international assistance. 

"Our projections indicate that we can expect a lot more heatwaves in the future due to climate change. The climatological data, as well as mentions in the media indicate a lot more heatwaves having been reported in South Africa alone, than what is reported by EM-DAT."

South Africa has a good observation network compared to most of the continent, where observations are sparse.  "In other parts of Africa, picking the events will be made difficult by a lack of ground observations. There is therefore a need for an increase in the number of observing stations in Africa in general. These will not only help with observing heatwaves, but they will help with climate studies in general, calibration of satellite estimates, and they will improve the input used to initialise models that provide us with weather forecasts." 

Scientific papers that link health with temperature point to a limitation in the available studies or data. "So not only are there challenges in meteorological data, we also have challenges with accessing health data. "There is a need for heatwave events and their impacts to be reported more, to assist with policy developments and climate change adaptation strategies," she says.    

Siberia heat influenced by humans

The prolonged Siberia heat from January to June 2020 would have been almost impossible without the influence of human-caused climate change, says a team of climate scientists.

Temperatures in Siberia have been more than 5°C above average from January to June, and up to 10°C above average in June. This has contributed to the first half of the year being the second warmest on record.

A temperature of 38°C was recorded in the Russian town of Verkhoyansk on June 20, north of the Arctic Circle.

Prolonged heat would happen less than once in every 80000 years without human-induced climate change, said the scientists. Climate change increased the chances of the prolonged heat by a factor of at least 600.

Even in the current climate, the prolonged heat was still unlikely: such extreme conditions can be expected to occur less than once every 130 years.

A hotter climate can have devastating effects, not just on the local wildlife and people who live there, but also on the planet’s climate system as a whole.

The Saturday Star

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