29 August 2017, Carbon Brief, Media reaction: Hurricane Harvey and climate change. Hurricane Harvey continues to rock the southern US, where at least nine people have died after unprecedented flooding. The events around Houston, Texas have sparked early debate over the links between the hurricane and climate change. Commentary from scientists suggests that warming is likely to have intensified its impact. Above-average sea surface temperatures in the Gulf of Mexico provided more energy and moisture for the developing hurricane, they say. And sea level rise ensured a larger storm surge at the coast and prevented floodwater from draining more quickly. Nevertheless, many other factors are likely to have played a role. These include Houston’s population explosion, continued building in flood-prone areas and subsidence due to groundwater over-extraction, media reports suggest. What role does climate change play? Alongside the swath of news coverage on Hurricane Harvey and the devastation it has caused, much of the reporting has delved into the question of where climate change fits in. Most articles highlight that the impact of climate change on hurricanes has many different strands. As the New York Times points out, “the relationship between hurricanes and climate change is not simple. Some aspects are known with growing certainty. Others, not so much.” To help unpick the details, journalists have been quizzing climate scientists, quoting them widely in recent days. Some scientists have also penned guest articles. Read More here
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29 August 2017, Climate Home, Hurricane Harvey: lawyers warn of climate lawsuits over damages. Hurricane Harvey is wreaking unprecedented damage on Texas. Should city planners, government agencies and businesses have seen it coming? Could they have prevented death and disruption by acting differently? Increasingly, such questions will be litigated in courtrooms and rely on climate science to answer, three environmental lawyers wrote in the journal Nature on Monday. Advances in the science of linking weather extremes to global warming has the potential to change the legal landscape, they write. The more clearly scientists can demonstrate an event was foreseeable, the more victims can – and will – seek redress from negligent authorities. “In a world where events like Hurricane Harvey are predicted to increase, and predicted confidently by scientists… courts will be called upon more and more to disentangle these issues,” co-author Sophie Marjanac, an Australian-qualified lawyer with Client Earth, told Climate Home. Marjanac give examples of potential targets for lawsuits. In Houston, Texas, developers were allowed to build on wetlands that otherwise would have helped to drain floodwaters. If it can be shown those decisions endangered people and property – and failed to anticipate known climate risks – the relevant authorities could be on the hook for payouts, she said. Read more here
28 August 2017, VOX, The “500-year” flood, explained: why Houston was so under prepared for Hurricane Harvey. It’s the city’s third “500-year” flood in the past three years. It’s difficult to comprehend the scale of the flooding and devastation that Hurricane Harvey and its aftermath are wreaking on the Houston area. Weather experts call the storm unprecedented, and note that it’s gone beyond even the most pessimistic forecasts. In the final reckoning, it’s certain that Harvey will be classified a 500-year flood — and maybe even a 1,000-year flood. But those terms can be a bit misleading — especially when high-profile people, like the president of the United States, confuse the issue by calling Harvey “a once in 500 year flood.” In theory, a 500-year flood is something that has a 1-in-500 shot of happening in any given year — in other words, the sort of event that’s so rare that it might not make sense to plan around the possibility of it happening. The problem is that 500-year floods are happening more often than probability predicts — especially in Houston. And, especially in Houston, prevention planning hasn’t evolved to acknowledge that a “500-year” flood isn’t really a 1-in-500 chance anymore. “500-year” floods are based not on history, but on probability. The severity of floods tends to get put in terms of years: a 100-year flood, a 500-year flood, a 1,000-year flood. But this isn’t an assessment of “the worst flood in” that time — places like Houston don’t actually have detailed weather records going back to 1017 AD, after all. Read More here
28 August 2017, Climate Home, Link between Hurricane Harvey and climate change is unclear. Reports the devastating storm was made worse by humanity’s carbon emissions fail to grasp climate change is not just about warming. The unprecedented amount of rainfall accompanying Hurricane Harvey immediately raised the question whether and to what extent climate change is to blame. In a warming world the vapour capacity of the atmosphere increases, and more extreme rainfall, like Texas is witnessing right now, is to be expected as a result. This leads many to conclude that climate change exacerbated the impacts of hurricane Harvey. It is very appropriate to highlight that this is the kind of event we expect to see more of in a warming world. However, to apply this argument directly and attribute (and quantify) the impacts from Harvey itself to human-induced climate change, neglects that climate change is not just about warming. In a changing climate, two effects come together: not only does the atmosphere warm up (thermodynamic effect) but the atmospheric circulation, which determine where, when, and how weather systems develop, can change as well (dynamic effect). Changes in the atmospheric circulation can increase the thermodynamic effect (as we saw during floods Louisiana in 2016) or act in the opposite direction to the thermodynamic effect, leading to locally decreasing the risk of extreme rainfall or canceling the effect of the warming alone (examples here). Dynamical factors and thermodynamic aspects of climate change can interact in complex ways and there are many examples where the circulation is as important as the thermodynamics. Read More here