Risks from extreme weather ‘significant and increasing’

27 November 2014

Exposure of human populations to extreme weather is set to increase as global climate and population size, location and age continue to change, according to Resilience to extreme weather, a new Royal Society report published today.

The report presents new maps showing the combined impact of climate and demographic changes across the world on the exposure of people to extreme weather. The maps highlight those areas where there is the greatest increased risk of populations being vulnerable towards to end of the century.

The report focuses on the risks to people from floods, droughts and heatwaves. These are some of the most frequent and damaging extreme events that currently occur and their impacts will change with the changing climate. It shows:

  • Increasing population numbers in areas that are exposed to extreme weather events exacerbate the risks from floods and droughts in many regions, but especially East, West and Central Africa, India and South-East Asia.
  • Over-65s are one of the groups most vulnerable to heatwaves. As a result of changes in the climate, the number of heatwave exposure events they experience each year could be up to three times larger by 2100. However, the number of over-65s is also increasing. By the end of the century, the combination of climate change and population change could lead to more than 10 times the number of annual heatwave exposure events currently suffered by over-65s. 
  • Changes in temperature and humidity could result in significant reductions in ability to work outdoors across much of Africa, Asia, and parts of North, South and Central America. This would impact rural communities and food production for a growing global population.

The report calls for action at all levels of government – international, national and local – to make society more resilient to extreme weather events. In 2015 important international agreements will be reached on disaster risk reduction, sustainable development and climate change. These agreements will be much more effective in addressing extreme weather and its impacts if they are linked with, and reinforce, each other.

Professor Georgina Mace, Chair of the working group for the report said:

“We are not resilient to the extremes of weather that we experience now and many people are already extremely vulnerable.  If we continue on our current trajectory the problem is likely to get much worse as our climate and population change. By acting now, we can reduce the serious risks to our children and grandchildren.

“National governments have a responsibility to do everything in their ability to protect their people from the devastation caused by extreme weather events.”

Between 1980 and 2004 the total cost of extreme-weather related events came to US$1.4 trillion (of which only ¼ was insured). Populations in countries with a low Human Development Index make up only 11% of those exposed to hazards but account for 53% of disaster mortality.

The report compares various practical options for the most effective and affordable defence against the impacts of flooding, drought and heatwaves.

The report concludes that engineered options, such as dams, sea walls and wells are often the most effective at reducing the impact of a particular hazard, but that they are also expensive, and if they fail they fail cataclysmically. If used in combination with ecosystem-based approaches such as floodplain or mangrove re-establishment and planting vegetation they can be more effective and affordable as well as delivering wider benefits on an on-going basis – not just when the hazard strikes. These ecosystem or ‘natural’ approaches are often more affordable and can have multiple additional benefits to society.

The working group therefore recommends that ecosystem-based approaches are increasingly used in combination with more traditional approaches, although more effort is needed to ensure they are systematically monitored and evaluated. The report uses the ‘Slowing the Flow’ initiative in Pickering, UK as an example of where this is being done.

Dr Nancy Grimm, of Arizona State University, who is a member of the working group for the report said:

“We need to make sure that large-scale engineering isn’t making us too complacent. In the developed world we have been heavily reliant on some key large-scale pieces engineering projects, which have been pushed to their limits during recent events. By using a combination of engineering and more natural approaches we can accept occasional small 'failures' while limiting the detrimental impact of a large, catastrophic event. We call this a safe-to-fail approach.”

The report also calls for changes to global financial accounting and regulation to ensure that extreme weather risk is made explicit. At present, these risks are not systematically factored into investors’ valuations or assessed by creditors.

Business surveys, economic forecasts and country briefings that guide investment decisions and credit ratings are typically based on the availability of skilled labour, access to export markets, political and economic stability, and financial incentives – but there is little or no consideration of actual or potential exposure to disaster risks.

Specifically, the Society suggests that companies report the following:

  • 1 in 100 (1%) risk per year – a stress test for a company’s solvency that evaluates the maximum probable losses expected for events that occur, on average, once in a hundred years or have a 10% chance of occurring every decade
  • 1 in 20 (5%) risk per year – a stress test for a company’s annual earnings
  • Annual Average Loss – a standardised metric for a company’s exposure to extreme events

Mr Rowan Douglas, member of the working group for the report said:

“If two otherwise identical international companies have different resilience to extreme weather risks that would impact their potential solvency or profit, for example one has unprotected factories located in high risk floodplains, then one should have a proportionately lower share price or valuation to reflect this higher financial risk. However, this rarely happens.

“As the frequency and severity of extreme events is increasing, there is increasing exposure of assets to risk. This brings an ever larger disconnect between material risk and asset valuation. Unless financial reforms are made to correct this, we will condemn ourselves to building vulnerable cities in the coming decades at the cost of millions of lost lives and livelihoods and billions of lost dollars, often across regions and communities that can least afford these catastrophic setbacks.”