An Illustrated History of Extreme Weather Attribution
By Kai Kornhuber & Amy Howden-Chapman
Extreme Weather Attribution
Twenty thousand related deaths, vast losses of livestock and wildfires, water shortages, and the decimation of agricultural productivity across the European continent. This stock-take reads like a post-apocalyptic disaster scenario, but the event was far from fictional. The 2003 heatwave was the most fatal “natural” disaster in recent European history and the severity of the event was, to a large degree, fuelled by anthropogenic emissions of greenhouse gases. How can destruction be so firmly linked to human actions? The connection was made explicit in peer-reviewed articles such as those by Peter Stott, Myles Allen and colleagues. These concluded that it was now possible to estimate the degree to which human activities had increased the risk of such a heatwave, thus initiating a new sub-discipline within climate science: Extreme Weather Event Attribution – from here on, attribution.
Attribution requires climate modelling in which weather extremes are simulated in computer models based under two conditions, factual and counterfactual. Factual scenarios represent the world as it currently is – affected by an increased level of greenhouse gases and a corresponding level of global mean temperature increase. Counterfactual scenarios on the other hand assume a world that ‘would have been’ not affected by human influences in the otherwise identical models. Comparing those two allows for estimating the human contribution to a specific weather extreme. At present this method is most reliable for heat extremes, as models exhibit good skill in the relevant processes and the response of heat extremes to a global mean temperature increase is mostly unambiguous (see Peter Watson in Issue 1 of The Anthroposphere)
Now, fifteen years and 30 ppm of additional carbon dioxide later, the number of attribution studies has sharply increased, alongside the frequency of record-breaking extreme weather events due to largely unmitigated emissions. Today, climate attribution analysis exists in various forms ranging from the dedicated annual report issued by the Bulletin of the American Meteorological Society (BAMS) to the almost real-time attribution from the World Weather Attribution Project at ECI Oxford. Indeed, even the increased risk in human mortality during the aforementioned 2003 summer heat waves can now be reliably estimated.
Thus, the question repeatedly posed to scientists during an extreme event – ‘Was this heat wave fuelled by climate change?' – can be answered with increasing confidence. With extreme weather attribution, weather has lost its innocence.
Lived Experiences of Climate Change
Global climate change is challenging to comprehend as it exceeds the human imagination in both temporal and spatial scales. As climate change and its impacts are mostly felt via its extremes, attribution studies provide the all-important bridge between scientific knowledge and Ordinary Knowledge. The latter term, drawn from the works of Science and Technology Studies scholar Sheila Jasanoff, can be understood as characterized as awareness rooted in lived experience. Attribution humanizes and localizes data and scientific evidence, thereby going some distance to recognising global climate change and its devastating implications as a lived experience.
This localization of climate effects is key to motivating a political response to climate action. People need to see ‘their’ lived event linked to the wider phenomenon of climate change, as a prelude to taking action. As Elinor Ostrom and her colleagues concluded in their research on common pool resource management, it is communities in which a local environment is personally valued where community members are more inclined to take defensive action against perceived threats.
Through influencing the narrative of lived experiences, attribution can therefore transform how climate change is understood – and make a quantifiable link between an abstract concept and our tangible present.
Timing is crucial for making such connections between first-person knowledge and global climate systems.
Early attribution studies, such as that by Peter Stott and colleagues and those collected in the special issues of the Bulletin of the American Meteorological Society, were published with a significant time lag – at least a year – after the event in question occurred. In recent years, there has been a major reduction of the time between events themselves and the attribution of those events to human activities. Today, attribution studies are increasingly being produced during the extreme event they seek to reflect. This elimination of a time lag has been made possible through a combination of factors including a better understanding of climatic processes, more sophisticated models, and increased computing power. Primarily, this reduction is due to the emergence of dedicated research projects. For example, with projects like ECI Oxford’s weather@home, computing power is aggregated by members of the public who donate the processing power of their home computers to help run intensive climate models.
The links between anthropogenic climate change and hurricane Florence, which hit the United States in September 2018, were made in real time. Anthropogenic climate change manifested as warmer sea surface temperatures and additional moisture available in the atmosphere, which led to an estimated 50 percent increase in rainfall relative to the counterfactual world. The rains brought by Florence caused an estimated damage of $22 billion to the U.S. states of North and South Carolina, the wettest tropical cyclone recorded in that region.
Communicating Climate Change
Democratising discussions of the link between specific weather events and climate change has the potential to have climate knowledge disseminated not just by experts but by a range of social actors. It has been noted by Simon Bushell that “who conveys a narrative is vital.'' The public has a far greater chance of believing climate knowledge when that knowledge comes from ‘relatable’ people, such as those perceived as being of a similar background or demographic. In the same way that the weather is often an accessible part of daily conversation, the shared experience of an extreme weather event can also become a universal talking point (a cultural phenomenon explored in Ben Lerner’s 2014 novel 10:04). The quick estimation of anthropogenic contributions to an individual extreme has opened up new possibilities for climate change communication. If a direct link between a weather extreme and greenhouse gas emissions can be made while those events are still being discussed as part of the news cycle and on the ground, the impact of a specific event in illustrating the wider turn of events is strengthened.
As part of these new developments, TV Weather presenters are put in the position of presenting information on climate change. Such presenters are widely trusted across the ideological spectrum and have a platform which reaches a large audience. Traditionally, meteorologists were shy about addressing climate issues, just as climate scientists were careful about overemphasizing a single extreme weather event. Extreme weather event attribution has helped to break this barrier. We are now seeing increased collaboration between weather presenters – who are usually meteorologists by training – and climate scientists. This can be seen in Australia’s Monash Climate Change Communication Research Hub which produces climate graphics to be inserted into weather-broadcast segments. This project acts to localize climate trends and contextualize extreme weather events as one element of a broader climate story. Many weather presenters have accepted this new role: ‘Climate without borders’ is an international network of weather presenters dedicated to educating weather presenters in climate change communication. Under the hashtag #MetsUnite meteorologists coordinate to show Prof. Ed Hawkins’ Warming Stripes, in order to raise awareness of the long-term increase in annual mean temperatures worldwide. Timely attribution helps weather presenters move from speculation to quantified statements. It is for this reason that large national weather services such as the UK Met Office, the German DWD and the Dutch KNMI are also planning to incorporate attribution in their weather forecast schemes.
The Future of Attribution
Improved climate change communication can lead to more informed citizens who will in turn demand more political action and be increasingly immune to disinformation campaigns from industry or status-quo interest groups. Already, in many places around the world politicians are being faced by demands during elections or on the streets to align political action with the emission goals of the Paris Agreement: to pursue efforts to limit end-of-century global mean warming to 1.5°C. Current projections to date instead point towards 3.5 to 4°C or more.
Increasingly, legal action is being taken to pressure policymakers to bring legislation in line with scientific findings on necessary emission cuts, as seen in 2018 when the Dutch government was forced to increase emission reductions. In putting a number on a specific weather extreme, future attribution studies might help to provide necessary information for loss and damage compensation. This increases the likelihood that those actors who contributed to either an increased frequency of a certain type of event or its amplified severity might have to face liability. How to quantify that liability exactly is still to be decided (see "The Changing Face of Environmental Litigation" by Ming Zee Tee in Anthroposphere). Even in advance of legal rulings, such companies could face reputational and other risks and it should also be noted that entities that fail to prepare for climate extremes, whether they contributed to emissions or not, could also face legal and reputational risks.
In August of 2018, Sweden among many regions in the northern hemisphere, experienced wildfires and severe hot and dry conditions, with temperatures exceeding the extremes of 2003. In the midst of this destruction, FridaysForFuture, a students climate protest, that since has been growing into a global movement was initiated in Stockholm, not far from where the wildfires ravaged. Unlike in 2003, in summer 2018 scientists were prepared and an attribution statement was issued while the heatwave was ongoing, estimating the likelihood of the 2018 heat wave to be “more than two times higher today than if human activities had not altered climate”. A finding later confirmed by Martha Vogel and colleagues, adding to the public conversation at a critical juncture. A year later, as summer temperatures again sent heat records falling like dominos, the extremes were rapidly contextualized with attribution studies – 20 times more likely, 100 more likely. Attribution studies continue to provide in case after case evidence to what should be common knowledge: in this new era of extremes, virtually every heat extreme is amplified in its harm by anthropogenic warming.
Amy Howden-Chapman is an artist, writer and co-founder of The Distance Plan.org, a platform that works for climate action through collaboration across the arts, sciences, policy, and activism. Her work has been exhibited internationally and her writing has appeared in venues including Urban Omnibus, Counterfutures, and Landfall. Howden-Chapman was the 2016 DAAD fellow at the Potsdam Institute for Climate Impact Research, Germany, and she currently teaches at the Harry Van Arsdale Jr. Center for Labor Studies, SUNY, Empire State, New York City.
Kai Kornhuber is a Postdoctoral Researcher at the Earth Institute, Columbia University, New York. Kai received his Ph.D. in Climate Physics from the Potsdam Institute for Climate Impact Research (PIK) and the University of Potsdam, Germany. Before joining Columbia University, Kai worked as a Postdoc at the Atmospheric Oceanic and Planetary Physics Department at the University of Oxford. His research is dedicated to internal mechanisms of the large-scale atmospheric circulation, their links to extreme weather events and their future evolution under ongoing climate change.
All photographs and composite images by Amy Howden-Chapman unless otherwise credited.
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