Climate Change and Extreme Weather: The Science of Event Attribution

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With extreme weather becoming increasingly frequent, there is one particular question that logically follows – Did climate change cause these events? As recent as a decade ago scientists would have confidently argued that this question cannot be answered, but thanks to rapid improvements in both the understanding of weather systems and the analytical methods used to study them, they are now able to provide some more meaningful responses.

But even with this new knowledge it’s still not possible to answer the exact question above, as the the question itself is flawed. No weather event ever has a single cause, in fact there are multiple, independent factors, most of which are natural. Climate change is but one variable in many, and it’s influence can be quite subtle.

So what can the scientists tell us? Well, according to a report from the National Academies of Science, Engineering, and Medicine (NASEM) released on March 11th, they can now examine how the likelihood and intensity of an event have been altered. And thus, the science of “event attribution” is born!

However, even when scientists are armed with their new understanding and analytical methods, statements and predictions can’t be made without a HUGE amount of data to back it up. This can be obtained in many ways, with some studies using observational data obtained from similar events in the past, and others using climate and weather models to compare conditions in worlds with and without human-caused climate changes. But no one data set is perfect, and the NASEM report states that results are often most reliable when multiple methods are used.

SO! We now have a rough idea of what event attribution is and how this new area of science works. Let’s start looking at what it can do! So far, the most reliable attribution findings that scientists can give us are for those related to temperature. There is little doubt in the scientific community that human activities have had a noticeable impact on this aspect of the climate, and it’s effect on various weather events are already known.

Apart from increasing the likelihood of extremely hot days and doing the opposite for cold days, a warmer climate can have some rather unexpected effects. Such warming can cause greater evaporation of water from the Earth’s surface, which not only increases the intensity of droughts, but also the amount of atmospheric moisture available to storms. This could lead to more severe heavy rainfall and snowfall events, and you can find an explanation of how that would work in another post I’ve written on the formation of snow.

But the implications of event attribution go beyond simply determining the influence of human-caused climate change. By gaining a deeper understanding of what causes extreme weather events, scientists can improve their ability to accurately predict and project future weather and climate states. If they’re able to predict both the frequency and intensity of extreme events, it could help lessen their impact by avoiding the destruction they could cause. For example, an accurate prediction may allow a community to evacuate long before the event even arrives, and knowledge regarding it’s frequency can help them decide between rebuilding or relocating.

It should now be quite clear what the science of event attribution can offer us, but we should also be aware of the challenges that this relatively new science faces. According to the NASEM report statements about event attribution are quite sensitive to the way the questions are framed, as well as their context. Given this sensitivity, many choices need to be made about defining the duration of the event, the geographical area impacted by it, what variables to study and many more. These decisions will likely drastically improve reliability, as they can all influence how results are interpreted.

But despite it’s problems, the science of event attribution has a lot it can offer to society in terms of limiting the impact of extreme weather, as well as drawing people’s attention to the reality of climate change. Real extreme weather events get people’s attention, and attribution studies could bring an end to the notion of climate change as a distant threat, and help people realise that there is a very real need for us to act on it now. Let’s just hope it can do it fast enough.

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