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
Tag Archives: Extreme Events
21 August 2017, The Conversation, Dry winter primes Sydney Basin for early start of bushfire season. It might feel like the depths of winter, but Australian fire services are preparing for an early start to the bushfire season. Sydney has been covered with smoke from hazard reduction burns, and the New South Wales Rural Fire Service has forecast a “horrific” season. Predicting the severity of a bushfire season isn’t easy, and – much like the near-annual announcements of the “worst flu season on record” – repeated warnings can diminish their urgency. However, new modelling that combines Bureau of Meteorology data with NASA satellite imaging has found that record-setting July warmth and low rainfall have created conditions very similar to 2013, when highly destructive bushfires burned across NSW and Victoria. Crucially, this research has found we’re approaching a crucial dryness threshold, past which fires are historically far more dangerous.How to measure bushfire fuel On September 10, 2013 several bushfires in Sydney’s West caused havoc well before the official start of the bushfire season. These were a precursor to fires that destroyed more than 200 properties a month later. Warm, dry winter weather had dried out the fuels in Sydney’s forests and bush reserves beyond “normal” levels for the time of year. The timing and severity of those preseason fires were a reminder that the region’s forests are flammable all year round; they can burn whenever the fuel they contain dries out past a certain threshold. Read More here
9 August 2017, The Conversation, Southeast Europe swelters through another heatwave with a human fingerprint. Parts of Europe are having a devastatingly hot summer. Already we’ve seen heat records topple in western Europe in June, and now a heatwave nicknamed “Lucifer” is bringing stifling conditions to areas of southern and eastern Europe. Several countries are grappling with the effects of this extreme heat, which include wildfires and water restrictions. Temperatures have soared past 40℃ in parts of Italy, Greece and the Balkans, with the extreme heat spreading north into the Czech Republic and southern Poland. Some areas are having their hottest temperatures since 2007 when severe heat also brought dangerous conditions to the southeast of the continent. The heat is associated with a high pressure system over southeast Europe, while the jet stream guides weather systems over Britain and northern Europe. In 2007 this type of split weather pattern across Europe persisted for weeks, bringing heavy rains and flooding to England with scorching temperatures for Greece and the Balkans. Read More here
2 August 2017, The Conversation, ‘Just do the weather’: does it matter if TV weather presenters aren’t experts? When Olympic swimming champion Giaan Rooney was asked to fill in presenting the weather segment on Melbourne’s Channel Seven weeknight news program just before Christmas 2012, she was taken aback. She pointed out that she knew nothing about weather and that her credibility was in sport. “Don’t worry, just do the weather,” was the reply from the network. Six weeks later, the 30-year-old Rooney was invited to continue in the role, replacing the 52-year-old presenter and trained meteorologist David Brown, who had been presenting on Seven for 20 years. As it turned out, Brown remained with the network and eventually went on to present the weather for Seven’s Sydney weeknight bulletin. But the switch from Brown to Rooney illustrates a dilemma that has never been resolved. Just who should present the weather on television? Weather presenters have long been a crucial component of any television news team, and are promoted as such. For many in the audience, they’ve also been the main conduit of weather information. Ten years ago 90% of Australians received at least some of their weather information from television. This has since fallen to 71%, according to a Bureau of Meteorology survey. But that’s still a lot of eyeballs. And with their segments usually perched at the end of bulletins, the extent to which weather presenters connect with viewers helps to determine whether their station can carry the valuable news audience over to the start of the next program. Read More here