(Bloomberg) -- Torrential rains that triggered floods and landslides have killed hundreds of people and displaced millions across parts of Africa, Europe and Asia in recent weeks.
The unprecedented deluges overwhelmed even communities accustomed to extreme weather and showed the limitations of the early-warning systems and emergency protocols established in many countries to avoid major loss of life.
Climate scientists have warned that an accelerated water cycle is locked into the world’s climate system due to past and projected greenhouse gas emissions, and is now irreversible.
The communities that tend to pay the highest price are almost invariably in poorer countries, where environments can be more fragile and governance more patchy, and there are fewer resources to bounce back after a disaster.
What’s been happening?
Record-breaking rainfall in September has driven nearly 3 million people from their homes and left 1,000 people dead in and around the Sahel region of Africa, and triggered mass evacuations and port closures around the Chinese megacity of Shanghai. Central Europe endured some of its worst flooding in years from Storm Boris, which caused €2 billion ($2.2 billion) to €3 billion in insured losses.
While death tolls from natural disasters tend to be lower in richer nations, the unexpected floods have found most countries unprepared. In 2021, at least 220 people lost their lives in Germany as a result of heavy rains and the resulting floods, a disaster that researchers found was made more likely by climate change.
Regions such as South Asia, which are historically familiar with violent bursts of rain, are struggling to cope too. In late July, landslides killed more than 300 people across the Wayanad district in the Southern Indian state of Kerala, after heavy rains battered its hills for hours. Landslides caused by similar weather conditions killed tens of people in the country’s mountainous North.
What is causing more frequent and intense rainfall?
In its latest review, United Nations scientific body the Intergovernmental Panel on Climate Change found that global warming was supercharging the planet’s water cycle and causing the weather to swing to increasingly severe extremes.
High concentrations of greenhouse gases in the atmosphere lead to rising temperatures on land and at sea. In turn, warmer oceans release moisture into the air through evaporation, feeding dense, vertical-shaped clouds that can discharge large amounts of rain quickly. In some cases, the volume of rainfall that usually occurs over one or two days ends up falling in two or three hours.
According to Deborah Brosnan, a marine and climate scientist who owns an environmental consulting firm in Washington, DC, air becomes capable of holding exponentially more moisture as it heats up, taking on 7% more water on average for every 1C of warming. “If you consider that we are now at 1.2C hotter, that amounts to heavy rainfall events being on average 8% more intense,” Brosnan said.
Why are extreme rainfall events becoming deadlier?
Many human settlements in both industrialized and developing countries weren’t designed to withstand the kind of intense and sustained rainfall that climate change has brought about. Many of those who die aren’t drowned but are buried under mud cascading off hills unable to absorb such high volumes of rainwater. Others are crushed inside collapsed houses.
Heavy rains often compound other impacts of climate change that make cities and cultivated areas more vulnerable. A study that mapped out climate-vulnerable hotspots in India found that areas more subject to hot spells tend to also experience more incidents of heavy rain. In such cases, if soil dries out due to a prolonged heat wave, it becomes more solid, making it harder for rainwater to seep through and exacerbating the risk of flooding.
Can climate science help communities cope with extreme weather?
Recent progress in climate science means it’s now possible to accurately gauge the role that climate change played in past extreme weather events, and to model future rainfall patterns so that governments in vulnerable areas can better prepare for the next deluge.
But the ability of communities to cope with flooding still depends on local circumstances such as levels of soil erosion and deforestation, the strength of bridges, dams and flood defenses, and poverty levels. There’s still no unified knowledge base that combines all these factors with climate vulnerabilities in order to identify the riskiest situations.
Who will pay the cost of more frequent extreme rainfall?
As the risks associated with global warming become more concrete and potentially expensive to deal with, some governments and businesses, particularly in Asia and Africa, are exploring new financial products to fund the cost of recovery.
One is parametric insurance, which pays out a set amount based on the magnitude of the event, not the magnitude of the losses — as is the case with traditional weather-related insurance policies.
Catastrophe bonds that pay out after a natural disaster is declared have grown in popularity in recent years.
Some governments in developing nations are also taking an interest in financial products that are triggered by less extreme cases of unusual weather. Average trading volumes for these listed “weather derivatives” jumped by more than 260% in 2023, according to the CME Group.
How is the threat from extreme rainfall evolving?
Scientists say their existing models may have underestimated the extent to which global warming is causing extreme rainfall, particularly in tropical regions. Few regions are likely to be spared the impact in coming years, with the IPCC pointing to Africa and Asia, North America and Europe as most at threat.
Beyond the immediate risk of destruction and loss of life, excess rain can also compromise food production as it plays a major part in soil erosion, depleting nutrients essential for agriculture and carbon sequestration. One study suggested that, by 2070, soil erosion worldwide may increase by as much as 35%.
Even after the rains stop and survivors are brought to safety, floods still represent a public health hazard.
Clean reservoirs can be contaminated by sewage, thus carrying diseases such as cholera, dysentery, typhoid and polio. Stagnant water bodies can become hotspots of vector-borne infection, spreading malaria or dengue through mosquitoes. The IPCC has warned that as the planet fast approaches the threshold of 1.5C of global warming, flooding events will become more frequent, and health action plans that include vaccine distribution and improved access to potable water among other measures should be put in place.
--With assistance from Lauren Rosenthal and Brian K. Sullivan.
©2024 Bloomberg L.P.
