15 August 2016, Washington Post, What we can say about the Louisiana floods and climate change. Here we are again, with a flood event upending the lives of large numbers of Americans and making everybody wonder about the role of climate change. In this case, it’s the stunning, multiday flooding in southern Louisiana that hit after a low pressure system combined with record amounts of atmospheric water vapor, dumping more than two feet of rainfall over three days in some places. At least 11 people were killed, and thousands have had to leave their homes.On Monday, climate researchers and weather experts were in what’s by now a familiar posture — explaining that, no, this event wasn’t “caused” by climate change, but then again, it’s precisely the sort of event that you’d expect to see more of on a warming planet. “Climate change has already been shown to increase the amounts of rain falling in the most intense events across many parts of the world, and extreme rainfall events like this week’s Louisiana storm are expected [to] grow increasingly common in the coming years,” wrote the Weather Underground’s Bob Henson and Jeff Masters. [‘The worst situation I’ve ever been through.’ Six killed, thousands displaced during historic Louisiana flooding] “Louisiana is always at risk of floods, naturally, but climate change is exacerbating that risk, weighting the dice against us,” Katharine Hayhoe, a climate researcher at Texas Tech University, told The Washington Post. “How long will it be until we finally recognize that the dice are loaded?” The easiest link between climate change and extreme weather events involves heat waves, arecent study by the National Academy of Sciences found. This makes sense: A warming planet overall breaks warm-temperature records more frequently than cold-temperature records and sets the stage for lengthier, or stronger, bouts of extreme heat. Read More here
Tag Archives: water
13 August 2016, Pacific Standard, America’s Latest 500-Year Rainstorm Is Underway Right Now in Louisiana. Observers are calling the record floods a “classic signal of climate change” — and high-resolution models predict another one to two feet of rain by Saturday evening. By mid-morning on Friday, more than a foot of rain had fallen near Kentwood, Louisiana, in just a 12-hour stretch — a downpour with an estimated likelihood of just once every 500 years, and roughly three months’ worth of rainfall during a typical hurricane season. It’s the latest in a string of exceptionally rare rainstorms that are stretching the definition of “extreme” weather. It’s exactly the sort of rainstorm that’s occurring more frequently as the planet warms. In response to the ongoing heavy rains, Louisiana Governor John Bel Edwards. declared a statewide state of emergency on Friday, and local governments aredistributing sandbags, conducting water rescues, and facilitating evacuations. The New Orleans Times-Picayune is maintaining a live blog of the latest developments. The Tickfaw River north of New Orleans soared 18 feet in about 12 hours to a new record crest on Friday morning, beating the water level of April 1983, and five feet higher than the high-water mark during Hurricane Isaac in 2012, the last hurricane to make landfall in Louisiana. Read More here
18 May 2016, The Conversation, Are toxic algal blooms the new normal for Australia’s major rivers? For much of this year, up to 1,700 kilometres of the Murray River has been hit by a serious outbreak of potentially toxic blue-green algae, which has flourished in the hotter-than-average conditions. After three months, the river is now recovering with the arrival of wet weather. But we are unlikely to have seen the last of these poisonous microbes. Large blue-green algal blooms are a relatively new phenomenon in inland waterways. In 1991 an algal bloom affected more than 1,000 km of the Darling River, the first time such an event had been reported in an Australian river, and one of the few times internationally. It was an environmental disaster, killing livestock and striking a telling blow against Australia’s reputation as a clean, green farming nation. The response was decisive: a state of emergency was declared, and the bloom ultimately gave rise to significant investment by state and federal governments into freshwater research, particularly in the Murray-Darling Basin. Why no emergency now? Fast forward two and a half decades to the latest bloom afflicting the Murray River, one of Australia’s most socially, economically and culturally significant waterways. The past decade has seen four similar blooms on the Murray River: in 2007, 2009, 2010 and now. Yes, they have garnered press attention, but there has not been the same call to arms that we saw when the Darling River was struck in 1991. It is almost as if such significant environmental events are now simply seen as the new normal. Why the apparent complacency? The 2007, 2009 and 2010 algal blooms on the Murray River all happened during the Millennium Drought, and hence were probably ascribed to an aberration in the weather. In reality, the situation may have more to do with how we manage water in Australia – particularly during periods of scarcity, such as the one we may well be entering now. Read More here
3 March 2016, Science Daily, Greenland’s ice is getting darker, increasing risk of melting. Feedback loops from melting itself are driving changes in reflectivity. Greenland’s snowy surface has been getting darker over the past two decades, absorbing more heat from the sun and increasing snow melt, a new study of satellite data shows. That trend is likely to continue, with the surface’s reflectivity, or albedo, decreasing by as much as 10 percent by the end of the century, the study says. While soot blowing in from wildfires contributes to the problem, it hasn’t been driving the change, the study finds. The real culprits are two feedback loops created by the melting itself. One of those processes isn’t visible to the human eye, but it is having a profound effect. The results, published in the European Geosciences Union journal The Cryosphere, have global implications. Fresh meltwater pouring into the ocean from Greenland raises sea level and could affect ocean ecology and circulation. “You don’t necessarily have to have a ‘dirtier’ snowpack to make it dark,” said lead author Marco Tedesco, a research professor at Columbia University’s Lamont-Doherty Earth Observatory and adjunct scientist at NASA Goddard Institute of Space Studies. “A snowpack that might look ‘clean’ to our eyes can be more effective in absorbing solar radiation than a dirty one. Overall, what matters, it is the total amount of solar energy that the surface absorbs. This is the real driver of melting.” The feedback loops work like this: During a warm summer with clear skies and lots of solar radiation pouring in, the surface starts to melt. As the top layers of fresh snow disappear, old impurities, like dust from erosion or soot that blew in years before, begin to appear, darkening the surface. A warm summer can remove enough snow to allow several years of impurities to concentrate at the surface as surrounding snow layers disappear. At the same time, as the snow melts and refreezes, the grains of snow get larger. This is because the meltwater acts like glue, sticking grains together when the surface refreezes. The larger grains create a less reflective surface that allows more solar radiation to be absorbed. The impact of grain size on albedo — the ratio between reflected and incoming solar radiation — is strong in the infrared range, where humans can’t see, but satellite instruments can detect the change. Read More here