Did climate change help spark the Syrian war?

Science Codex: A new study says a record drought that ravaged Syria in 2006-2010 was likely stoked by ongoing manmade climate change, and that the drought may have helped propel the 2011 Syrian uprising. Researchers say the drought, the worst ever recorded in the region, destroyed agriculture in the breadbasket region of northern Syria, driving dispossessed farmers to cities, where poverty, government mismanagement and other factors created unrest that exploded in spring 2011. The conflict has since evolved into a complex multinational war that has killed at least 200,000 people and displaced millions. The study appears today in the leading journal Proceedings of the National Academy of Sciences.

"We're not saying the drought caused the war," said Richard Seager, a climate scientist at Columbia University's Lamont-Doherty Earth Observatory who coauthored the study. "We're saying that added to all the other stressors, it helped kick things over the threshold into open conflict. And a drought of that severity was made much more likely by the ongoing human-driven drying of that region."

A growing body of research suggests that extreme weather, including high temperatures and droughts, increases the chances of violence, from individual attacks to full-scale wars. Some researchers project that manmade global warming will heighten future conflicts, or argue that it may already be doing so. And recent journalistic accounts and other reports have linked warfare in Syria, Iraq and elsewhere in part to environmental issues, especially lack of water. The new study, combining climate, social and economic data, is perhaps the first to look closely and quantitatively at these questions in relation to a current war....

A Bedouin tent in the Syrian desert, shot by yeowatzup yeowatz, Wikimedia Commons via Flickr, under the Creative Commons Attirbution 2.0 Generic license 

Climate change responsible for super-charging winter storms, scientists say

Suzanne Goldenberg in the Guardian (UK): Winters may be getting shorter, but watch out when it does snow: climate change is super-charging storms like the blizzard engulfing the American north-east, scientists said on Monday.

The heavier storms of recent years – snowfalls that shut down cities and brought heavy flooding to coastal areas of New England – carried the imprints of climate change, as researchers get better at detecting the fingerprints of global warming – even from snow.

It was too soon to pin the current storm to climate change, but a trend line was emerging, the scientists said. “The snow season is getting shorter,” said Kevin Trenberth, a climate scientist at the National Center for Atmospheric Research. “But the interesting thing is you can end up with heavier snows in part because of climate change.”

In general, climate change produces more extreme precipitation in North America – and if it’s cold enough, that produces snow. ... Nor’easters pack their punch from the contrast between cold land temperatures at the warmer Gulf stream and surrounding waters. Five of New York’s biggest snow storms have occurred since 2000, and 2014 was the hottest year in 130 years of temperatures records.

...“You can easily get as much as 20% more snow out of a storm than you would otherwise, as long as it is cold enough so that all of that moisture gets converted into snow. And that is usually the case in the wintertime,” Trenberth said....

NASA image of the current visitor to Carbon Based headquarters, January 27, 2015

Global warming's influence on extreme weather

A press release from Stanford University: Extreme climate and weather events such as record high temperatures, intense downpours and severe storm surges are becoming more common in many parts of the world. But because high-quality weather records go back only about 100 years, most scientists have been reluctant to say if global warming affected particular extreme events.

On Wednesday, Dec. 17, at the American Geophysical Union's Fall Meeting in San Francisco, Noah Diffenbaugh, an associate professor of environmental Earth system science at the Stanford School of Earth Sciences, will discuss approaches to this challenge in a talk titled "Quantifying the Influence of Observed Global Warming on the Probability of Unprecedented Extreme Climate Events." He will focus on weather events that – at the time they occur – are more extreme than any other event in the historical record.

Diffenbaugh emphasizes that asking precisely the right question is critical for finding the correct answer. "The media are often focused on whether global warming caused a particular event," said Diffenbaugh, who is a senior fellow at the Stanford Woods Institute for the Environment. "The more useful question for real-world decisions is: 'Is the probability of a particular event statistically different now compared with a climate without human influence?'"

Diffenbaugh said the research requires three elements: a long record of climate observations; a large collection of climate model experiments that accurately simulate the observed variations in climate; and advanced statistical techniques to analyze both the observations and the climate models.

One research challenge involves having just a few decades or a century of high-quality weather data with which to make sense of events that might occur once every 1,000 or 10,000 years in a theoretical climate without human influence.

But decision makers need to appreciate the influence of global warming on extreme climate and weather events. "If we look over the last decade in the United States, there have been more than 70 events that have each caused at least $1 billion in damage, and a number of those have been considerably more costly," said Diffenbaugh. "Understanding whether the probability of those high-impact events has changed can help us to plan for future extreme events, and to value the costs and benefits of avoiding future global warming."

Navarre Beach, Florida, after Hurricane Katrina in 2005. FEMA photo

Study counters case for climate change-violence link

Lou Del Bello in SciDev.net: Climate change is far from being solely to blame for violence in Sub-Saharan Africa, say researchers — other factors matter much more. Their paper, published on 10 November in the journal Proceedings of the National Academy of Sciences, contradicts earlier studies that found that higher temperatures are a major risk factor in conflict.

For instance, last year a different group concluded that a shift towards hotter conditions by a single statistical unit known as a ‘standard deviation’ — equivalent to, for example, warming an African country by 0.4 degrees Celsius for a year — caused a four per cent rise in the likelihood of personal violence and a 14 per cent increase in conflict between groups.

But now a team led by John O’Loughlin, a geographer at the University of Colorado Boulder in the United States, says that previous research may have overlooked other key triggers such as political instability, poverty and geographical conditions.

O’Loughlin’s team examined these factors alongside exceptionally hot or dry periods in Sub-Saharan Africa to assess the chances of increased violence. Breaking the area down into subregional grids, the researchers pinpointed 78,000 ‘conflict events’ from the past 33 years and matched them with weather conditions and social and geographical factors.

They found that conflicts such as riots, protests or violence against civilians were more common when temperatures were particularly high. But they also discovered an inconsistent relationship between temperature deviations on the one hand and different types of conflict and different subregions on the other.

And, more critically, they found that longer periods of higher temperatures and wet or dry conditions had less impact on conflict than other influences, such as recent nearby violence and a lack of democracy, says O’Loughlin....

A British jeep passes a sign warning against looting on the outskirts of Ravenna, Italy, 7 December 1944. From the Imperial War Museum

Scientists to ‘fast-track’ evidence linking global warming to wild weather

Tom Bawden in the Independent (UK): Scientists are to challenge the climate-change sceptics by vastly improving the speed with which they can prove links between a heatwave or other extreme weather event and man-made changes to the atmosphere.

It typically takes about a year to determine whether human-induced global warming played a role in a drought, storm, torrential downpour or heatwave – and how big a role it played. This allows climate sceptics to dismiss any given extreme event as part of the “natural weather variation” in the immediate aftermath, while campaigners automatically blame it on global warming. By the time the truth comes out most people have lost interest in the event, the Oxford University scientists involved in the project say.

They are developing a new scientific model that will shrink to as little as three days the time it takes to establish or rule out a link to climate change, in large part by using highly accurate estimates of sea surface temperatures rather than waiting for the actual readings to be published – a process that can  often take months.

“We want to clear up the huge amounts of confusion around how climate change is influencing the weather, in both directions.  For example, the typhoon in the Philippines that dominated the UN climate change talks in Warsaw last November and that many people put down to climate change – it turned out it had no detectable evidence. And the same goes for Hurricane Sandy,” Dr Friederike Otto, of Oxford University’s Environmental Change Institute, told The Independent.

But there are plenty of other cases where climate change is likely to have been involved, she said. Examples include last year’s record heatwave in Australia – the severity of which an eminent scientist concluded this week “was virtually impossible without climate change” – and the flooding in the UK at the start of the year, which Dr Otto’s department has just established was made 25 per cent more likely by global warming....

A smoky sunset in Albury, New South Wales, shot by Thennicke, Wikimedia Commons, under the Creative Commons Attribution-Share Alike 3.0 Unported license

New report finds human-caused climate change increased severity of 2013 heat waves in Asia, Europe and Australia

A press release from NOAA: A report released today investigates the causes of a wide variety of extreme weather and climate events from around the world in 2013. Published by the Bulletin of the American Meteorological Society, "Explaining Extreme Events of 2013 from a Climate Perspective" addresses the causes of 16 individual extreme events that occurred on four continents in 2013. NOAA scientists served as three of the four lead editors on the report.

Of the five heat waves studied in the report, human-caused climate chan
ge-primarily through the burning of fossil fuels-was found to have clearly increased the severity and likelihood of those events. On the other hand, for other events examined like droughts, heavy rain events, and storms, fingerprinting the influence of human activity was more challenging. The influence of human-caused climate change on these kinds of events was sometimes evident, but often less clear, suggesting natural factors played a far more dominant role.

"This annual report contributes to a growing field of science which helps communities, businesses and nations alike understand the impacts of natural and human-caused climate change," said Thomas R. Karl, L.H.D., director of NOAA's National Climatic Data Center. "The science remains challenging, but the environmental intelligence the report yields to decision makers is invaluable and the demand is ever-growing."

Confidence in the role of climate change about any one event is increased when multiple groups using independent methods come to similar conclusions. For example, in this report, five independent research teams looked at specific factors related to the record heat in Australia in 2013. Each team consistently found that human-caused climate change increased the likelihood and severity of that event. However, for the California drought, which was investigated by three teams from the United States, human factors were found not to have influenced the lack of rainfall. One team found evidence that atmospheric pressure patterns increased due to human causes, but the influence on the California drought remains uncertain....

More severe tornado outbreaks may be linked to climate change

Michael Roppolo in CBS News: Climate change may be playing a role in the strength and frequency of tornadoes, a new study suggests. Research published in the journal Climate Dynamics finds that although tornadoes are occurring fewer days per year than they used to, they are forming at greater density and strength. This means that on days when tornadoes do form, there tend to be more of them and they're often more powerful.

...In the past, many scientists dismissed the impact of climate change on tornadoes because tornado occurrences vary so greatly from year to year. The number of tornado days in a year -- days in which at least one tornado occurred -- have declined since the 1970s, with a high of 187 in 1971 and a low of 79 tornado days in 2013. But at the same time, the number of days with multiple tornadoes has risen sharply.

Using data from the Storm Prediction Center, Florida State University geography professor James Elsner and his colleagues studied tornadoes with EF-1 intensity and stronger. Elsner told CBS News that when he first looked at tornado days with at least four tornadoes, he noted no change. However, when he looked at instances with larger numbers of tornadoes in a single day, he found a significant increase.

..."The bottom line is that the risk of big tornado days featuring densely concentrated tornado outbreaks is on the rise," the study states.

The researchers say their findings suggest climate change may be a factor. "These trends represent observational evidence of changes in severe deep moist convection possibly related to our changing climate," they write....

A tornado in Quail, Texas

New research links tornado strength, frequency to climate change

Kathleen Haughney at Florida State 24/7: New research by a Florida State University geography professor shows that climate change may be playing a key role in the strength and frequency of tornadoes hitting the United States.

Published Wednesday in the journal Climate Dynamics, Professor James Elsner writes that though tornadoes are forming fewer days per year, they are forming at a greater density and strength than ever before. So, for example, instead of one or two forming on a given day in an area, there might be three or four occurring.  "We may be less threatened by tornadoes on a day-to-day basis, but when they do come, they come like there's no tomorrow," Elsner said.

Elsner, an expert in climate and weather trends, said in the past, many researchers dismissed the impact of climate change on tornadoes because there was no distinct pattern in the number of tornado days per year. In 1971, there were 187 tornado days, but in 2013 there were only 79 days with tornadoes.

But a deeper dive into the data showed more severity in the types of storms and that more were happening on a given day than in previous years. "I think it’s important for forecasters and the public to know this," Elsner said. "It's a matter of making sure the public is aware that if there is a higher risk of a storm, there may actually be multiple storms in a day."

The United States experiences more tornadoes than any other country, and despite advances in technology and warning systems, they still remain a hazard to residents in storm-prone areas. The 2011 tornado season, for example, had nearly 1,700 storms and killed more than 550 people.

So far, in 2014, there have been 189 storms with a death toll of 43, according to the NOAA/National Weather Service Storm Prediction Center. One bright spot of news in the research, Elsner added, was that the geographic areas impacted most regularly by tornadoes do not appear to be growing...

NOAA image of a tornado near Minco, Oklahoma, date unknown

Australia's drying climate caused by greenhouse gases, study finds

Click Green (UK): US Government scientists have developed a new high-resolution climate model that shows southwestern Australia's long-term decline in fall and winter rainfall is caused by increases in manmade greenhouse gas emissions and ozone depletion.

"This new high-resolution climate model is able to simulate regional-scale precipitation with considerably improved accuracy compared to previous generation models," said Tom Delworth, a research scientist at NOAA's Geophysical Fluid Dynamics Laboratory in Princeton, N.J., who helped develop the new model and is co-author of the research published today.  "This model is a major step forward in our effort to improve the prediction of regional climate change, particularly involving water resources."

NOAA researchers conducted several climate simulations using this global climate model to study long-term changes in rainfall in various regions across the globe. One of the most striking signals of change emerged over Australia, where a long-term decline in fall and winter rainfall has been observed over parts of southern Australia.

Simulating natural and manmade climate drivers, scientists showed that the decline in rainfall is primarily a response to manmade increases in greenhouse gases as well as a thinning of the ozone caused by manmade aerosol emissions.  Several natural causes were tested with the model, including volcano eruptions and changes in the sun's radiation. But none of these natural climate drivers reproduced the long-term observed drying, indicating this trend is due to human activity.

Southern Australia's decline in rainfall began around 1970 and has increased over the last four decades. The model projects a continued decline in winter rainfall throughout the rest of the 21st century, with significant implications for regional water resources. The drying is most severe over southwest Australia where the model forecasts a 40 percent decline in average rainfall by the late 21st century....

In the Wheatlands, Australia, shot by Phillip Capper, Wikimedia Commons via Fllickr, under the Creative Commons Attribution 2.0 Generic license

Warm Pacific may paradoxically cause US winter freeze, says a study

Reuters: Unusually warm western Pacific waters linked to global warming may be the paradoxical cause of a bone-chilling winter in parts of the United States this year, a scientific study said on Thursday. The theory contrasts with other experts' views, including that the freeze was simply a freak natural event or that it was linked to a thawing of the Arctic in recent years that sent a blast of cold air south.

"People's reaction when they sit under 10 feet of snow is to say 'this cannot be man-made climate change'," said Professor Tim Palmer of Oxford University, who published his research in the journal Science. "But there is a plausible link," he told Reuters.

He said a strengthening of trade winds had led to a build-up of warm water in the western tropical Pacific, aggravated in recent years by global warming from man-made emissions of greenhouse gases. Thunderstorms linked to the warmth in turn disrupted the jetstream, high altitude winds which flow in vast meandering loops around the northern hemisphere, and sucked cold air from the Arctic. Detroit, for instance, suffered record snows and the coldest January since 1977.

Pinpointing the causes of the U.S. chill, when climate change should make cold winters less likely, would help companies, farmers, city planners or even home owners wondering if they should invest in extra roof insulation. Two other experts were unconvinced by Palmer's study.

Jennifer Francis of Rutgers University, who wrote in 2011 that a melting of Arctic ice may cause cold snaps, said the Pacific had a similar pattern of heavy rainfall in 2011-12 but the winter was mild in the United States....

A winter storm in New York City, MTA of the state of New York, Wikimedia Commons via Flickr, under the Creative Commons Attribution 2.0 Generic license

Extended California fire season confirms severity of climate change

Haya El Nasser in Al-Jazeera America: The climate change debate currently pits the bulk of the scientific community against holdout deniers who don't believe rising temperatures are the result of human activity. But in California, a state suffering from a historic drought, why the phenomenon is happening is less important than the simple fact that it is.

Forecasters and fire agencies have now tossed aside their normal fire calendar – mid-May to mid-October – and prepare for what some call a “new normal” of a greatly extended fire season. They are hiring extra staff and issuing more warnings. Some local officials have warned that fire season in some parts of California is basically a year-round phenomenon now.

The National Weather Service has been issuing an unprecedented number of fire forecasts and alerts in the thick of the usually-wet season, months earlier than normal. Its forecast offices have kicked into fire-season mode well ahead of schedule.

The Sacramento office, which issues fire forecasts for interior Northern California, decided last week to up its daily seven-day forecasts to twice a day, and its National Fire Danger Rating System, which measures the seriousness of fire conditions, is going out earlier. “Climatology shows us we’ve been getting warmer and a little drier,” said Michelle Mead, warning coordination meteorologist in Sacramento. “The fire season is not what it used to be 10 years ago.”

Research papers linking climate change to a persistent drought – which has parched California three years in a row – have been making the rounds among fire forecasters, said Brett Lutz, meteorologist and climate program manager for the National Weather Service in Medford, Ore. “Climate change for the first time was actually a topic of conversation that was presented and discussed at length” in a recent meeting, he said....

A 2009 fire in California, shot by Rennett Stowe, Wikimedia Commons via Flickr, under the Creative Commons Attribution 2.0 Generic license

Is global warming just a giant natural fluctuation? Nope

A press release from McGill University: An analysis of temperature data since 1500 all but rules out the possibility that global warming in the industrial era is just a natural fluctuation in the earth’s climate, according to a new study by McGill University physics professor Shaun Lovejoy.

The study, published online April 6 in the journal Climate Dynamics, represents a new approach to the question of whether global warming in the industrial era has been caused largely by man-made emissions from the burning of fossil fuels. Rather than using complex computer models to estimate the effects of greenhouse-gas emissions, Lovejoy examines historical data to assess the competing hypothesis: that warming over the past century is due to natural long-term variations in temperature.

“This study will be a blow to any remaining climate-change deniers,” Lovejoy says. “Their two most convincing arguments – that the warming is natural in origin, and that the computer models are wrong – are either directly contradicted by this analysis, or simply do not apply to it.”

Lovejoy’s study applies statistical methodology to determine the probability that global warming since 1880 is due to natural variability. His conclusion: the natural-warming hypothesis may be ruled out “with confidence levels great than 99%, and most likely greater than 99.9%.”

To assess the natural variability before much human interference, the new study uses “multi-proxy climate reconstructions” developed by scientists in recent years to estimate historical temperatures, as well as fluctuation-analysis techniques from nonlinear geophysics. The climate reconstructions take into account a variety of gauges found in nature, such as tree rings, ice cores, and lake sediments. And the fluctuation-analysis techniques make it possible to understand the temperature variations over wide ranges of time scales.

...While his new study makes no use of the huge computer models commonly used by scientists to estimate the magnitude of future climate change, Lovejoy’s findings effectively complement those of the International Panel on Climate Change (IPCC), he says. His study predicts, with 95% confidence, that a doubling of carbon-dioxide levels in the atmosphere would cause the climate to warm by between 2.5 and 4.2 degrees Celsius. That range is more precise than – but in line with -- the IPCC’s prediction that temperatures would rise by 1.5 to 4.5 degrees Celsius if CO2 concentrations double....

Ice floes shot by michael clarke stuff, Wikimedia Commons via Flickr, under the Creative Commons Attribution-Share Alike 2.0 Generic license 

Linking storms to climate change a ‘distraction’, say UK experts

A press release from the University of Manchester: Writing in the journal Weather, Climate and Society, the University of Manchester researchers argue that cutting greenhouse gas emissions, while crucial to reducing humanity’s longer-term impact on the planet, will not eliminate violent storms, tornadoes or flooding and the damage they cause.

The authors suggest that developing greater resilience to extreme weather events must be given greater priority if the socioeconomic impact of storms, like those that have ravaged Britain this winter, is to be reduced. Professor David Schultz, one of the authors of the guest editorial, said: “One of the long-term effects of climate change is often predicted to be an increase in the intensity and frequency of many high-impact weather events, so reducing greenhouse gas emissions is often seen to be the response to the problem.

“Reducing humanity’s impact on our planet should be pursued as a matter of urgency, but more emphasis must also be placed on being resilient to individual weather events, as this year’s storms in Britain have so devastatingly shown.”

...Schultz, a professor of synoptic meteorology, and co-author Dr Vladimir Janković, a science historian specialising in weather and climate, say the short-term, large variability from year to year in high-impact weather makes it difficult, if not impossible, to draw conclusions about the correlation to longer-term climate change.

They argue that while large public investments in dams and flood defences, for example, must account for the possibilities of how weather might change in the future, this should not prevent short-term thinking to address more immediate vulnerability to inevitable high-impact weather events.

“Avoiding construction in floodplains, implementing strong building codes, and increasing preparedness can make society more resilient to extreme weather events,” said Dr Janković. “But compounding the problem is that finding money for recovery is easier than spending on prevention, even if the costs of recovery are much higher.”...

This aerial images was taken approximately two miles west of Rockfish (town) along Rt. 617. The Rockfish River flooded the surrounding low lands. In another Nelson County location, up to 27" of rain in four eight hours from Hurriacne Camille was recorded. No. 69-2133, Virginia Governor's Negative Collection, Library of Virginia. Flickr Commons

Global warming slowdown 'does not invalidate climate change'

Adam Vaughan in the Guardian (UK): The slowdown in rising global surface temperatures is not a sign that climate change is no longer happening, the national science academies of the US and the UK have said. Publishing a guide on the state of climate change science, the National Academy of Sciences and the Royal Society said the short-term slowdown this century did not "invalidate" the long-term trend of rising temperatures caused by man-made climate change.

"Despite the decadal slowdown in the rise of average surface temperature, a longer-term warming trend is still evident. Each of the last three decades was warmer than any other decade since widespread thermometer measurements were introduced in the 1850s," the publication, Climate Change Evidence and Causes, said.

Scientists have been investigating reasons for the slowdown in temperature rises. Peer-reviewed papers over the last year have suggested 17 sun-dimming volcanic eruptions since 2000, "unusual" trade winds in the Pacific Ocean burying surface heat deep underwater and the world's oceans absorbing greater amounts of heat in recent years may have contributed.

Thomas Stocker, the co-chair of working group one of the UN's climate science panel, said at the launch of the Intergovernmental Panel on Climate Change's landmark report last September that the recent slowdown in surface temperature rises was not significant because it was over too short a period of time. "Climate relevant trends should not be calculated for periods of less than 30 years," he said.....

A painting by Lazlo Mednyanszky (1852-1919), "Snow Landscape with Boats"

UK weather: changing jet stream linked to flooding crisis

Tom Revell in Blue and Green Tomorrow: The system of winds that is responsible for bringing weather to Northern Europe and North America may be changing, new research has found. A study suggests that the jet stream, a high-speed air current that carries weather around the globe, is taking a longer, more meandering route than usual. This means that weather patterns will remain the same in some areas for longer periods.

If accurate, these findings could explain the recent stormy spell that has brought devastating flooding to many parts of the UK. “This does seem to suggest that weather patterns are changing and people are noticing that the weather in their area is not what it used to be”, said Prof Jennifer Francis of Rutgers University in the US. “We can expect more of the same and we can expect it to happen more frequently.”

It has been suggested that the jet stream has been affected by the warming of the Arctic region, caused by manmade climate change. Francis said that it was too early to definitively confirm the link, but added, “As we have more data I do think we will start to see the influence of climate change.”

Speaking on the BBC’s Andrew Marr Show on Sunday, defence secretary Philip Hammond said climate change was “clearly a factor” in the prolonged stormy period. Labour leader Ed Miliband has also partly blamed a lack of government spending in the fight against climate change for the crisis.

“What we’ve learnt from what’s happened over the last few weeks, tragically, is that the costs of not acting on climate change in terms of the billions of pounds that are lost in terms of businesses and families as well as the human costs are greater than the costs of acting”, he said, also speaking on Sunday....

Stormy skies over Poole Harbour in September 2013, shot by Ian Kirk, Wikimedia Commons via Flickr, under the Creative Commons Attribution 2.0 Generic license

Expert warns of link between warming climate and extreme weather

ABC News (Australia): A senior lecturer in environmental studies at the University of Newcastle says there is a link between a warming climate and extreme weather events. Dr Liam Phelan addressed a gathering in Newcastle yesterday as part of National Climate Action Day.

He says while recent bushfires across NSW and the typhoon in the Philippines are not solely caused by climate change, the occurrence of such events is more likely with warming conditions. Dr Phelan says all extreme weather events are affected by climate change in some way.

"The link between climate change and extreme weather events is intuitive enough, if you're playing cards and you're dealt a bad hand well that's just chance right, anybody can get a bad hand but if you're play cards and the deck is stacked against you than you've got a much greater chance of getting a bad hand," he said.

"And when that happens over and over and over again then you start to ask questions about why that's so."..

Smoke over Sydney during a 1994 fire, shot by Daduschu, under the Creative Commons Attribution-Share Alike 3.0 Unported license

Scientists find precipitation, global warming link

Anne Stark at the Lawrence Livermore National Laboratory:... A new study by Lawrence Livermore National Laboratory scientists shows that observed changes in global (ocean and land) precipitation are directly affected by human activities and cannot be explained by natural variability alone. The research appears in the Nov. 11 online edition of the Proceedings of the National Academy of Sciences.

Emissions of heat-trapping and ozone-depleting gases affect the distribution of precipitation through two mechanisms. Increasing temperatures are expected to make wet regions wetter and dry regions drier (thermodynamic changes); and changes in atmospheric circulation patterns will push storm tracks and subtropical dry zones toward the poles.

"Both these changes are occurring simultaneously in global precipitation and this behavior cannot be explained by natural variability alone," said LLNL's lead author Kate Marvel. "External influences such as the increase in greenhouse gases are responsible for the changes."

The team compared climate model predications with the Global Precipitation Climatology Project's global observations, which span from 1979-2012, and found that natural variability (such as El Niños and La Niñas) does not account for the changes in global precipitation patterns. While natural fluctuations in climate can lead to either intensification or poleward shifts in precipitation, it is very rare for the two effects to occur together naturally.

"In combination, manmade increases in greenhouse gases and stratospheric ozone depletion are expected to lead to both an intensification and redistribution of global precipitation," said Céline Bonfils, the other LLNL author. "The fact that we see both of these effects simultaneously in the observations is strong evidence that humans are affecting global precipitation."

Marvel and Bonfils identified a fingerprint pattern that characterizes the simultaneous response of precipitation location and intensity to external forcing....

Rain clouds over Liverpool, shot by Stuart, Wikimedia Commons via Flickr, under the Creative Commons Attribution 2.0 Generic license

Extreme weather linked to climate change

Rosanne Skirble in Voice of America: No evidence has linked extreme weather events to climate change, until now. New research suggests devastating floods, droughts and storms were exacerbated by human-induced climate change caused by the burning of fossil fuels in our cars, factories and homes. The new report, released by British and American climate agencies, analyzes a dozen extreme weather events which occurred worldwide in 2012.

“What they find is [with] about half of the events," said Thomas Karl, director of the NOAA National Climatic Data Center, "the analyses reveal compelling evidence that human-caused change was a factor contributing to the extreme event.” 

The National Oceanic and Atmospheric Administration (NOAA) and Britain’s Met Office Hadley Centre edited the report. Co-editor and NOAA scientist Thomas Peterson says natural weather patterns and human induced climate change are factors in the intensity and evolution of events.

While last year’s spring and summer heat waves in the United States are attributed to normal atmospheric dynamics, climate scientists found that is not the entire story. “They estimated that human caused climate change contributed about one-third of the magnitude of that warmth," Peterson said. "Or in terms of risk, greenhouse warming had already made very large seasonal departures from normal, like the temperatures in the spring in the Eastern U.S. about 12 times more likely to occur.”

The report also blamed human-caused climate change for the warmer ocean and atmosphere that drove the loss of sea ice in the Arctic....

In New Orleans' Lower Ninth Ward after Hurricane Katrina, 2005, shot by Infrogmation, Wikimedia Commons, under the Creative Commons Attribution 2.5 Generic license.

Human activity obscures the causes of Texas floods

Iowa Now (the University of Iowa): Periodic flooding in Texas—one the most flood-prone states in the nation—cannot be firmly linked to climate change due to numerous dams and other manmade structures introduced over the years, according to a University of Iowa study. The researchers also found that tropical cyclones are less responsible for major floods in the region than in the eastern United States.

The study, which looked at 70 years of records, appears in the August 2013 issue of the Journal of the American Water Resources Association. Lead author Gabriele Villarini, assistant professor in the Department of Civil and Environmental Engineering and assistant research engineer at IIHR-Hydroscience & Engineering, indicates that although the problem is severe, the causes of Texas flooding are less clear.

“In this study, we examined the time series of the largest flood peaks every year from 62 stations in Texas with a record of at least 70 years,” he says. “We were interested in examining whether flood magnitudes changed during the study period and, if so, what was the cause of these changes. We found that most of the changes we detected were related to human modification of the catchments and more specifically to river regulation.”

He points out that there are more than 7,100 permitted dams in Texas, with some 2,000 of them designed for flood control. “We also examined the link between flooding and tropical cyclones. Tropical cyclones are an important flood agent with regionally varying effects. However, they are not associated with the largest flood events to the same degree we found for the eastern United States,” he says.

Historically, Texas experiences frequent flooding, resulting in numerous fatalities and extensive property damage. In fact, Villarini says, studies show that Texas led the nation in flood-related injuries and fatalities during the period from 1959 through 2005 and that Texas is the only state with fatalities occurring every year from 1960 through 2002...

NOAA photo of flooding from Hurricane Allison in 2001

Recent devastating wildfires could be result of climate change

RedOrbit: The larger, more destructive wildfires devastating some regions of the western US could be fueled by climate change, according to new research appearing in the Journal of Applied Meteorology and Climatology.

These erratic fires are more difficult to contain, as well as more dangerous to people living in the area and likely to cause catastrophic damage, lead author and Michigan State University assistant professor of geography Lifeng Luo and his colleagues said. Furthermore, they predict that the trend is likely to continue.

As Luo said Thursday in a statement, “Our findings suggest that future lower atmospheric conditions may favor larger and more extreme wildfires, posing an additional challenge to fire and forest management.”

...The increased size of the wildfires is mainly driven by natural factors, such as the availability of fuel (vegetation), precipitation, wind and the location of lightning strikes, the researchers explained. Specifically, they found that extremely dry and unstable conditions in the earth’s lower atmosphere will continue contributing to “erratic and extreme fire behavior.”

Furthermore, Luo and co-authors Ying Tang and Shiyuan Zhong from Michigan State, and Xindu Bian and Warren Heilman from the US Forest Service also wrote that “global climate change may have a significant impact on these factors, thus affecting potential wildfire activity across many parts of the world.”...

The Bambi Bucket attached to a Ch-47 Helicopter from the 2-149th, Texas National Guard, dumps water on a blaze nearing property. Texas National Guard crews launched out of the Austin Army Aviation Facility to fight wild fires threatening homes and property near Bastrop, Texas, September 6, 2011. Photo by Staff Sgt. Malcolm McClendon