What’s the role of human-caused climate change in disasters?
Climate Change Climate models Extreme weather

What’s the role of human-caused climate change in disasters?

Prof Dr Ilan Kelman
Prof Dr Ilan Kelman

In 10 seconds? Extreme weather and its impacts are often attributed to human-caused climate change, while researchers are looking for solid proof of cause and effect. A new paper develops and examines a technique for this, but questions remain regarding its applicability.

What does this research say? Its goal was to offer a better way to establish to what extent human activity drives extreme weather events. And, the authors believe that their method improves on the ‘classic attribution framework’. Thus, experts would be able to determine the human factor in certain compound events - for example, in the case of extreme heat stress and air pollution - and help assess the compound risk linked to climate change.

How solid are their findings? As I suggested in the introduction, the results are mixed. The paper’s method was a simple model extending the single-variable analysis to two variables simultaneously and suggesting that many other variables could easily be added. (This would be useful because the climate is a complex system affected by a host of variables.) In the current paper, many assumptions were made. The first is that climate change affects only the mean (average) of each variable's probability distribution (Let me decode that for you: in statistics, it describes the possible values of a variable in a given range. Example: the probability distribution of temperature in Pennsylvania in May is likely to be between 58°F and 88°F.)

OK, and what’s the problem with it? The problem is, that it's difficult to accept this assumption. A good example is fire weather in Canada – with fires starting on days when temperatures reached the extreme end of the 'distribution'. Researchers, therefore have already suggested using other, so-called Bayesian statistical approaches. A second major assumption is that the dependence between the two variables remains the same under climate change. This is an inadequate choice when considering heatwaves, with their projected mortality due to climate change.

But does this method address the issue? As I said, the results are mixed. Another recent study explains how disasters are caused by vulnerability rather than by weather, no matter how the weather is affected by climate change. These authors argue that blaming disasters on climate, climate change, and weather are political choices about politicized decisions to avoid responsibility and real action. These conclusions have been foundational baselines from the beginning of research into climate, climate change, and disaster links, such as through a foundational paper and book, neither of which is cited in the new publication.

Putting climate in place among causes of migration from Senegal (Ribot et al., 2020)
Putting climate in place among causes of migration from Senegal (Ribot et al., 2020)

Meaning that we do not need to worry about weather-related disasters under climate change? Again, this is where “mixed” comes in! The new paper makes a major mistake by lumping heat waves with all other weather and not mentioning humidity. This is despite ample evidence of the direct, devastating impacts on deaths, agriculture, and food of heat-humidity exacerbated by human-caused climate change to the point that humans cannot survive outdoors. The current heatwave in India and Pakistan is an example of what we face.

So, should we link extreme weather to climate change? We can link it, but the priority should be this: we should act on ensuring that no weather, extreme or otherwise, is involved in disasters, irrespective of climate change. Aside from the deaths and injuries averted by stopping disasters, cost-benefit analyses demonstrate how much money is saved. For a flood warning system in Nepal, the benefit-cost ratio was between 24 and 73 (in other words, very good) when accounting for climate change, saving each household over $1,000 per flood on a yearly 70¢ investment. In Los Angeles, taking measures against sea-level rise for individual properties in two locations would, under all sea-level rise scenarios, result in hundreds of millions of dollars of savings in terms of net present value.

Not all measures are necessarily helpful

For building a sea wall and moveable gates along part of the Texan coast to reduce storm surge damage, a 50-to-100-year lifetime yielded benefit-cost ratios of 0.99-3.23 (any value above 1.00 means the investment brings a benefit)

This calculation did not account for previous analyses, especially for the US, on how relying on such structures tends to make people accept flooding, so they are less prepared when major floods happen to cause more significant damage.

Plus, the Texas study highlights the irony of the fact that higher storm surge is expected due to human-caused climate change, primarily from fossil fuel use… while the proposed interventions are meant to protect Houston’s oil infrastructure.

Ilan has curated 14 research articles out of 5 saving you 56 hours of reading time.

The Science Integrity Check of this 3-min Science Digest was performed by Dr. ASM Mainul Hasan.

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