Southern California is losing its clouds, increasing the risk of more intense wildfires

May 31, 2018 by  
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The elevated summer temperatures in California  are causing decreased levels of the low-atmosphere clouds that were once common throughout the southern coastal regions of the state. A new study has found that because these clouds are dissipating from the increased heat, the region is now facing an increased risk of wildfire . “Clouds that used to burn off by noon or 1 o’clock are now gone by 10 or 11, if they form at all,” bioclimatologist and study lead author Park Williams told . Due to a warming climate and an expanding urban heat island, cloud cover is trapped in a positive feedback loop where less clouds mean higher temperatures, and higher temperatures mean less clouds. Published in the journal Geophysical Research Letters , the new study concludes that there has been a 25 to 50 percent decrease in low-lying summer clouds since the 1970s. “ Cloud cover is plummeting in southern coastal California,” said Williams, “and as clouds decrease, that increases the chance of bigger and more intense fires.” The low-lying stratus clouds in the area typically form in the early morning in a thin, wet layer of coastal air that exists between land and drier air masses. The increased heat from climate change and the urban heat island effect has caused the clouds to dissolve earlier in the day, leaving little cover during the hottest parts of the afternoon. Related: The growing wine industry is threatening California’s Napa Valley To study the changes in cloud cover, Williams and his team analyzed hour-by-hour cloud data gathered by California airports over the past several decades. The data was then compared with vegetation moisture data from the U.S. Wildland Fire Assessment System. This comparison enabled the team to conclude that the decreased cloud cover has led to an increased wildfire risk. “Even though the danger has increased, people in these areas are very good at putting out fires, so the area burned hasn’t gone up,” Williams explained. “But the dice are now loaded, and in areas where clouds have decreased, the fires should be getting more intense and harder to contain. At some point, we’ll see if people can continue to keep up.” +  Geophysical Research Letters Via Images via Depositphotos (1, 2)

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Southern California is losing its clouds, increasing the risk of more intense wildfires

Climate change could make cities 8C hotter by 2100, new studies show

May 31, 2017 by  
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Climate change is raising temperatures , but the impact could be worse in the world’s cities . Researchers say the urban heat island effect – or the fact that cities are hotter thanks to human activity – combined with climate change could increase temperatures in urban areas by around 14.4 degrees Fahrenheit, or eight degrees Celsius, by the end of the 21st century. Three researchers led by Francisco Estrada of the Universidad Nacional Autónoma de México and the Institute of Environmental Studies projected city temperatures could rise by around five degrees Celsius due to climate change, as well as an additional two or three degrees Celsius as asphalt and concrete crowd out parks and lakes in metropolises, inducing the urban heat island effect. Such increased temperatures could impact human health and burden natural resources . Related: New NOAA tool shows how climate change will affect your neighborhood As major cities prepare for the impacts of climate change, many of them likely haven’t been considering the urban heat island effect. The researchers said many impact estimates don’t include the effect. So they drew on average planetary warming projections combined with the effect, and used data from 1,692 of Earth’s biggest cities between 1950 and 2015, to determine the economic costs of climate change. They also built their research on worse case scenarios: if carbon emissions continue to rise instead of declining. The results aren’t pretty: cities hit the hardest could lose 10.9 percent of GDP by 2100. Only around one percent of the planet’s surface is covered with cities, but the urban centers produce around 80 percent of gross world product. Around 78 percent of the energy consumed worldwide happens in cities. They also generate over 60 percent of global carbon emissions from burning fossil fuels . Cities have a chance to act on the research now – mitigating the urban heat island effect by taking actions like planting trees ; green roofs could help too. The journal Nature Climate Change published the research online this week. Via The Guardian Images via Pixabay and Wikimedia Commons

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Climate change could make cities 8C hotter by 2100, new studies show

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