Climate change: the human factor
04 March 2019 | Story Jorisna Bonthuys. Read time 8 min.
The recent drought which left dams like the Theewaterskloof Dam dangerously empty, and saw the City of Cape Town's taps almost run dry, can now be expected once every 15 years – rather than every 50 years as previously assumed. Photo Wikimedia.
The University of Cape Town (UCT) is driving cutting-edge research to quantify the long-term effects of humans on global warming, aimed at not only reducing future risk but also enhancing on-the-ground responses to reduce the impact on populations of the global south.
African Climate and Development Initiative (ACDI) director Professor Mark New is co-leader of the international, multidisciplinary research team working to change the status quo which has seen very few extreme-event attribution studies conducted in Africa.
This field of science determines how human influence on the global climate system – known commonly as global warming – is changing the intensity and frequency of weather extremes. To now, most attribution studies have been done in the global north.
New's work, funded by financial service provider BNP-Paribas Foundation in terms of its Climate Initiative programme, combines the strengths of scholars from UCT, the University of Oxford and Lawrence Berkley National Laboratory in the United States. It also relies on African climate experts and emerging researchers from South Africa, Benin, Nigeria, Liberia and Kenya.
"This is cutting-edge science led by African researchers, for African application," he said, adding that the research is specifically examining weather extremes that lead to water-related risks, initially focusing on drought.
"Climate change poses serious development challenges for Africa, from both the greenhouse gas emissions reduction and adaptation to climate risk perspectives.
"For [climate] adaptation, African countries are among the most vulnerable to climate change and variability."
Site-specific vulnerabilities
Recent droughts in southern Africa serve as a stark reminder of the region's susceptibility to the effects of climate change, New pointed out.
The research team is analysing the extent to which climate change impacts on society, and how much is due to site-specific vulnerabilities.
"These models allow us to simulate a world with and without human-driven climate change. We can then compare weather events of interest between these modelled worlds."
"This cutting-edge, joint-attribution research enables us to move from just looking at weather risk to a more integrated understanding of how changing weather risk propagates into impacts on the ground. This also provides information on how we might change our on-the-ground responses to minimise the impacts," New explained.
The team uses sophisticated models to detail how the climate system has evolved in recent decades under the influence of humans.
"These models allow us to simulate a world with and without human-driven climate change. We can then compare weather events of interest between these modelled worlds," he said, adding that this comparison allows them to quantify the changes in climate risk over time.
This work is relevant in many ways, according to New. It can inform investment in adaptation and risk reduction, support new climate finance mechanisms and insurance instruments, and help African countries benefit from global financial flows and investment in low-carbon, climate-resilient development.
The 2015 to 2017 drought in the Western Cape – the worst in a century – has served as a backdrop for much of the innovative attribution science performed at UCT. This research, part of New's work as the holder of the AXA Research Chair in African Climate Risk, has already yielded valuable new insights that enable him and his team to look at a more comprehensive set of climate-related risks, including heat waves, wildfires and flooding.
Interestingly, the science shows that the effect on rainfall of climate change due to the impact of humans on nature rendered this particular drought in the province about three times more likely to occur than would otherwise have been the case.
"Global warming increased the chances of this event threefold," New said.
Climate-induced disasters
The research also underlines how the frequency of a drought of this extent has changed over time because of human influence on climate. Such a drought, which saw the City of Cape Town's taps almost run dry, can now to be expected once every 15 years – rather than every 50 years as previously assumed.
"Both the frequency and severity of climate-induced disasters are changing, often for the worse. For the Western Cape, the extent, duration and seasonal distribution of rainfall seem to be changing.
The impact of drought and climate change on a future secure water supply for populations of the global south is potentially very serious. Photo Daniel McGahey.
"Along with higher temperature levels and more evaporation, the implications of drought and climate change for river flows and long-term assurance of water supply are potentially serious," he warned.
Additionally, while the likelihood of a drought this severe remains rare, the risk will increase with further warming.
"This is part of the 'new normal' we have to start getting used to in a warmer and drier world due to the impact of global warming on our regional climate."
Even in the best-case scenario, the Western Cape – like the rest of South Africa – is expected to become more vulnerable to food and water insecurity in the coming decades. This ups the urgency of implementing the best and most cost-effective adaptation plans in order to increase local resilience.
New said the ACDI's African attribution science research plays a vital role in informing the planning of water management systems within the context of drier and hotter regional conditions which increase the risk of failing water resource systems.
"In theory, the Western Cape's water resource system should be reliable 49 out of every 50 years, but its designers did not completely consider the changing climate risk profiles. This is potentially an adaptation blind spot," he cautioned.
"Both the frequency and severity of climate-induced disasters are changing, often for the worse."
"Given that both the severity and the likelihood of extreme events are changing, our systems need to be designed to ensure reliability."
The ACDI researchers are also considering adaptation and management responses to changes in climate risk in the region, including catchment restoration, securing the ecological infrastructure, and ecosystem-based adaptation.
This work involves conducting case studies in the Berg and uMngenwater catchment regions in South Africa, among others. The catchments that are being investigated have undergone extensive land-cover change over the past 50 years, thanks to a significant, and measurable, human footprint.
"We hope this work will deliver real-world examples of the [potential] return on investment in adaptation interventions [aimed at reducing] loss and damage caused by climate change in Africa," New said.
"We need to make informed investment decisions going forward. We also need to understand the benefits of implementing certain strategies and how exactly these strategies are reducing vulnerability, given the changing nature of climate risk in the region.
"It will also contribute to emerging global debates on loss and damage – the first steps to quantifying the human contribution to damage caused by climate-related events."
Read more about the ACDI's work.
Mapping future climate pathways in sub-Saharan Africa 28 Feb 2019
Pioneering climate-change curricula in southern Africa 26 Feb 2019
African partnership for climate resilience 25 Feb 2019
Boosting SA's climate change readiness 22 Feb 2019
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