Saturday, November 7, 2015

Half of Weather Disasters Linked to Climate Change

Members of an alpine club were caught in heavy snowfall in Nepal during an October, 2014 ascent from Tilicho Lake to their base camp near Annapurna Massif. Snowstorms were more likely in Nepal last year because of human-induced climate change, according to a global team of scientists. 

By Randy Lee Loftis, National Geographic 

From a deadly snowstorm in Nepal to a heat wave in Argentina that crashed power supplies, at least 14 extreme weather events last year bore the fingerprints of human-induced climate change, an international team of scientists reported Thursday.

Researchers examined 28 weather extremes on all seven continents to see if they were influenced by climate change or were just normal weather. Their conclusion: Half of them showed some role of climate change.

“We hope that this will help people see how climate change is affecting their day-to-day lives,” says lead editor Stephanie C. Herring of the National Oceanic and Atmospheric Administration’s National Centers for Environmental Information.

This detective work hasn’t been possible until recently because science wasn’t up to the task, leaving a gap in society’s ability to adapt to climate change linked to greenhouse gases, which come from burning of fossil fuels and other human activities.

Although debate continues over accuracy and details, scientists now say their improved modeling tools in recent years have made it easier to tease out climate change effects from the seeming chaos of the weather.

Climate change plus local land use worsened prairie flooding in parts of Canada, according to a new scientific report.  In this July, 2014 photo, the swollen Assiniboine River covers farmland in Manitoba, Canada. 

he findings, by researchers from agencies and institutions in more than 20 countries, add to the list of extreme events in which climate change either played a large or small role or set up conditions that made them more likely. Record heat struck Europe, the Korean peninsula, northern China, and Australia – all with climate-change signals, according to the peer-reviewed report, which appears in a special issue of the Bulletin of the American Meteorological Society.

Droughts in Syria and East Africa, record rains in New Zealand and France, Nepal’s extreme Himalayan snowstorm, flooding in southeastern Canada, and an extremely active Hawaiian hurricane season also had direct or indirect climate links, the report finds. So did increased Antarctic sea ice and hotter Pacific and Atlantic sea-surface temperatures.

Scientists say their confidence has risen in the techniques used to link specific events to climate change, especially when it comes to heat waves. Extreme rainfall, on the other hand, is less likely to show a clear link to altered climate.

The same techniques can discount the link between climate change and extreme weather. The scientists detected no link in last year’s severe winter storms in the United Kingdom and North America or the unusually cold U.S. winter. And a look at Sao Paulo’s critical water shortage reveals a non-climate answer: Water planners hadn’t kept up with growing demands.

In Northern California, researchers could not link any single 2014 wildfire to climate change but they concluded that climate change has made bigger, more intense western fires far more likely, according to the new report as well as numerous other studies.

“They see quite clear evidence in this case,” says report co-editor Peter Stott of the U.K. Met Office Hadley Centre for Climate Science and Services.

Scientists say global warming played a role in extreme heat in Seoul, South Korea last year. 


Such findings will help people get ready for climate change’s impacts, NOAA’s Herring says.

“As the field of climate attribution science grows, resource managers, the insurance industry, and many others can use the information more effectively for improved decision-making and to help communities better prepare for future extreme events,” she says.

Here’s a global rundown of what the report finds about human-induced climate change and 2014’s extreme weather.

North America
Climate change plus local land use worsened prairie flooding in southeastern Canada. Hawaii’s hurricanes were “substantially more likely” because of climate change. So were Northern California’s wildfires. Very cold winters such as one in the upper Midwest in 2014 have become from 20 to 100 times less likely than in the 1880s. Climate change wasn’t linked to the East Coast’s cold winter or extreme winter storms that raked North America.

Africa and the Middle East
Climate change worsened a drought in East Africa and in the Levant region of southern Syria. No drought link was found in the rest of the Middle East.

Antarctic sea ice reached a record of nearly 7.8 million square miles in 2014 because winds carried cold air offshore, boosting ice production on the water. Climate change will make that less likely, the report finds.

Climate change played a role in extreme heat in Korea and China and made several disasters more likely, including flooding in Jakarta, a Nepal snowstorm that killed 43, and extremely high sea-surface temperatures in the western tropical and northeast Pacific Ocean. No climate change signals were found in droughts in northeastern Asia, China, and Singapore or the western Pacific’s active tropical cyclone season.

Climate change made the heat waves of 2014 substantially more likely and severe, according to the report. Extremely high pressure south of Australia, causing frost, low-elevation snowfall and less rain, also was more likely, as was an extreme, five-day rainfall in New Zealand.

Compared with 1950, climate change tripled the chance of extreme rainfall in southern France’s Cévennes Mountains. Record heat over Europe, the northeast Pacific, and the northwest Atlantic also was more likely. However, no climate fingerprints were found in winter storms and extreme rainfall in the United Kingdom or Hurricane Gonzolo’s transition into a storm that struck Europe.

South America

Human-induced climate change made Argentina’s heat wave five times more likely but southern Brazil’s water shortage was due to increased population and water demand.
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