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Getting Ready: Extreme weather leads to a new field of attribution science
By Susan Glick,
There is so much to learn about climate change. The volume of information can seem overwhelming, especially when we try to understand the role of climate change in severe weather events like hurricanes, catastrophic floods, hotter and more frequent heat waves, and even forest fires and glacier melts.
But what role does a warmer climate, caused by historically greater amounts of carbon in the atmosphere, actually play in these events? Searching the Internet for answers, I came upon an article from Columbia University’s Climate School and learned that climate change and its “unknowns” have led to a new scientific field called attribution science.
Recent severe weather events include hurricanes that make landfall in the southern United States, destroy shoreline communities and then move inland to flatten towns and flood farmlands. In other areas, fires spring and spread from dried-up forest floors to burn villages and take lives. Some places suffer prolonged power outages and disrupted water systems. We know such scenarios are happening with more frequency and at greater strengths. In other countries, as close as Greenland, glaciers are melting and causing an array of shifts in farmlands and communities. We know such events are caused by climate change, which is caused by historically high levels of carbon in the atmosphere.
But then we ask, how much more powerful are these recent weather events than storms of, say, 50 or 100 years ago? What is the actual impact of higher atmospheric carbon on major weather events? Do weather catastrophes happen solely because of increased carbon? Or, maybe, does carbon enhance natural weather events, making them extremely destructive and deadly? To what extent?
To answer such questions, climate scientists developed a new scientific field: attribution science. Attribution scientists caution that atmospheric carbon does not cause a severe weather event; it enhances it. These scientists determine the extent to which a weather event is strengthened by higher temperatures, which we know are the result of high levels of atmospheric carbon. Attribution scientists ask, “How does a storm or other severe event compare to a storm of a hundred years ago, and what does that mean for contemporary storms or floods?”
To answer such questions, an international group of scientists formed the “World Weather Attributions Initiative,” in which Columbia’s Climate School participates. The group analyzes a major weather event right after it occurs to figure out how it might have acted a century ago. Using computer models, they can develop data for each past year to show how human activity involving fossil fuels has affected greenhouse gas emissions, and thus the amount of carbon in the atmosphere for each year. With these statistics, attribution scientists can identify percent differences in storm strength and frequency, even indicating the percent likelihood of recurrence.
Attribution science is not precise, but it can indicate the likelihood of extreme weather events and the percent influence of carbon-warmed climate on the severity of such events. They know, for example, that climate change made the deadly Hurricane Harvey that hit Louisiana and Texas in 2017 three times more likely, increased rainfall by 15% and lasted longer than expected.
Attribution science is still developing as a scientific field, and its accuracy is more reliable for larger areas, such as swaths of 100x100 miles. Thus, their climate models are more accurate for events like heat waves or changes in Arctic ice. Scientists are still trying to understand the percent by which precipitation increases as a result of climate warming.
To learn more, attribution scientists are developing more sensitive computers to help identify more components of the atmosphere and predict with more accuracy the changes in various gases. Although attribution science will become more accurate as models are refined, scientists already know that climate change is from increased atmospheric carbon, which makes weather events more extreme: heavier rainfall, more intense storms, more extensive flooding, and more forest fires. In some places, high temperatures are causing glacier melts that result in flooding in historically dry areas, affecting communities and farmlands. (Effects of warming oceans in the Arctic and Antarctica are topics for another column.)
The basic culprit in all this weather-related mayhem is atmospheric carbon. Attribution science seems likely to lead to a better understanding of the impacts of our actions on climate events. We have only one Earth. The more we can limit our use of products and energy from fossil fuels, the better off we’ll be, with families that are healthier and more secure.
Susan Glick volunteers with York Ready for Climate Action. YRCA is a nonprofit 501c3 grassroots citizens’ organization dedicated to increasing awareness of the causes and effects of climate change and advancing environmentally friendly and inclusive policies and behaviors. Please see yorkreadyforclimateaction.org or email@example.com. Information about EcoHOMES is on the same site.