03/04/2017

Extreme Weather Events Linked To Climate Change Impact On The Jet Stream

Pennsylvania State University - A'ndrea Elyse Messer

Unprecedented summer warmth and flooding, forest fires, drought and torrential rain -- extreme weather events are occurring more and more often, but now an international team of climate scientists has found a connection between many extreme weather events and the impact climate change is having on the jet stream.
On the left is an image of the global circulation pattern on a normal day. On the right is the image of the global circulation pattern when extreme weather occurs. The pattern on the right shows extreme patterns of wind speeds going north and south, while the normal pattern on the left shows moderate speed winds in both the north and south directions. Credit: Michael Mann / Penn State
Unprecedented summer warmth and flooding, forest fires, drought and torrential rain — extreme weather events are occurring more and more often, but now an international team of climate scientists has found a connection between many extreme weather events and the impact climate change is having on the jet stream.
"We came as close as one can to demonstrating a direct link between climate change and a large family of extreme recent weather events," said Michael Mann, distinguished professor of atmospheric science and director, Earth System Science Center, Penn State. "Short of actually identifying the events in the climate models."
The unusual weather events that piqued the researchers' interest are things such as the 2003 European heat wave, the 2010 Pakistan flood and Russian heatwave, the 2011 Texas and Oklahoma heat wave and drought and the 2015 California wildfires.
The researchers looked at a combination of roughly 50 climate models from around the world that are part of the Coupled Model Intercomparison Project Phase 5 (CMIP5), which is part of the World Climate Research Programme. These models are run using specific scenarios and producing simulated data that can be evaluated across the different models. However, while the models are useful for examining large-scale climate patterns and how they are likely to evolve over time, they cannot be relied on for an accurate depiction of extreme weather events. That is where actual observations prove critical.
The researchers looked at the historical atmospheric observations to document the conditions under which extreme weather patterns form and persist. These conditions occur when the jet stream, a global atmospheric wave of air that encompasses the Earth, becomes stationary and the peaks and troughs remain locked in place.
"Most stationary jet stream disturbances, however, will dissipate over time," said Mann. "Under certain circumstances the wave disturbance is effectively constrained by an atmospheric wave guide, something similar to the way a coaxial cable guides a television signal. Disturbances then cannot easily dissipate, and very large amplitude swings in the jet stream north and south can remain in place as it rounds the globe."
This constrained configuration of the jet stream is like a rollercoaster with high peaks and valleys, but only forms when there are six, seven or eight pairs of peaks and valleys surrounding the globe. The jet stream can then behave as if there is a waveguide — uncrossable barriers in the north and south — and a wave with large peaks and valleys can occur.
"If the same weather persists for weeks on end in one region, then sunny days can turn into a serious heat wave and drought, and lasting rains can lead to flooding," said Stefan Rahmstorf, Potsdam Institute for Climate Impact Research (PIK), Germany.
The structure of the jet stream relates to its latitude and the temperature gradient from north to south. Temperatures typically have the steepest gradients in mid-latitudes and a strong circumpolar jet stream arises. However, when these temperature gradients decrease in just the right way, a weakened "double peak" jet stream arises with the strongest jet stream winds located to the north and south of the mid-latitudes.
"The warming of the Arctic, the polar amplification of warming, plays a key role here," said Mann. "The surface and lower atmosphere are warming more in the Arctic than anywhere else on the globe. That pattern projects onto the very temperature gradient profile that we identify as supporting atmospheric waveguide conditions."
Theoretically, standing jet stream waves with large amplitude north/south undulations should cause unusual weather events.
"We don't trust climate models yet to predict specific episodes of extreme weather because the models are too coarse," said study co-author Dim Coumou of PIK. "However, the models do faithfully reproduce large scale patterns of temperature change," added co-author Kai Kornhuber of PIK.
The researchers looked at real-world observations and confirmed that this temperature pattern does correspond with the double-peaked jet stream and waveguide patter associated with persistent extreme weather events in the late spring and summer such as droughts, floods and heat waves. They found the pattern has become more prominent in both observations and climate model simulations.
"Using the simulations, we demonstrate that rising greenhouse gases are responsible for the increase," said Mann.
The researchers noted in today's (Mar. 27) issue of Scientific Report that "Both the models and observations suggest this signal has only recently emerged from the background noise of natural variability."
"We are now able to connect the dots when it comes to human-caused global warming and an array of extreme recent weather events," said Mann.
While the models do not reliably track individual extreme weather events, they do reproduce the jet stream patterns and temperature scenarios that in the real world lead to torrential rain for days, weeks of broiling sun and absence of precipitation.
"Currently we have only looked at historical simulations," said Mann. "What's up next is to examine the model projections of the future and see what they imply about what might be in store as far as further increases in extreme weather are concerned."

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'Completely Unlivable': Climate Change Pushing Humans, Other Species To The Brink

Fairfax - Peter Hannam

Human societies and a multitude of species are going to be tested by climate change in ways that are barely understood, a wide-ranging study involving researchers from 44 institutions around the world has found.
Species in every ecosystem are being affected by rising temperatures and shifting rainfall patterns, with marine animals moving poleward at the average pace of 72 kilometres and land-based ones 17 kilometres a decade, according to the paper published on Friday in the journal Science.
Malaria and other mosquito-borne diseases are spreading as temperatures warm. Photo: AP
"Movement of mosquitoes in response to global warming is a threat to health in many countries through predicted increases in the number of known, and potentially new, diseases," the paper found, noting malaria is already a risk for about half of humanity, with more than 200 million cases recorded in 2014 alone.
Food security is also at risk from the spread of plant pathogens and other pests.
"This is going to impact on a lot more than you think," said Stephen Williams, a rainforest ecologist and one of the paper's authors.
While some species can adapt by moving either to higher ground or cooler waters, not all can. Human populations, too, are limited in how they can move, depending on how tightly national boundaries are enforced.
"[T]he relative immobility of many human societies, largely imposed by jurisdictional borders, has limited capacity to respond to environmental change by migration," the paper said.
While Australia is known for its fluctuating weather, particularly rainfall, more extreme conditions will challenge many human and animal communities alike. "We're going way outside the boundaries of our natural variability ... more than we appreciate," Professor Williams said.
Four hours above 29 degrees and a lemuroid ringtail possum will likely perish. Photo: Wet Tropics Management Authority.
He cited lemuroid ringtail possums that inhabit the wet tropics rainforests and will die if exposed to just four hours of 29-degree temperatures.
Heatwaves, if they coincide with dry conditions with little mist or cloud, "can literally crash a population in a number of days", Professor Williams said. "Suddenly it becomes completely unlivable."
The UN is seeking $US4.4 billion by the end of March to prevent catastrophic hunger and famine in South Sudan, Nigeria, Somalia and Yemen. Photo: WFP/AP
The shifting of the range of creatures poses challenges for conservation efforts not least because endangered species may exit areas set aside for their protection as they seek more hospitable habitat.
"Under climate change, everything is very dynamic and moving," Professor Williams said.
The biologically rich giant kelp forests off eastern Tasmania are under threat from warm-water predators. Photo: Craig Sanderson
In some cases, a threatened species will enter a region where it wasn't previously found, becoming "an invading species where by law it must be exterminated", he said.
Reducing greenhouse gas emissions "removes the root cause" of the problem. In the case of tropical rainforests, the number of species expected to disappear will drop from about 60 per cent by the end of the century under business-as-usual emissions to as few as 5 per cent. "It will make a really big difference," he said.
On-going monitoring is needed to track how species are moving, including across state or national boundaries. The collected evidence is limited and, in some cases, being interrupted by funding cuts.
"[L]ong-term datasets for biological systems are rare, and recent trends of declining funding undermine the viability of monitoring programs required to document and respond to climate change," the paper found.
Researchers in a range of Australian programs are awaiting news of their fate, with the federal government due to announce within weeks the next round of funding for the National Collaborative Research Infrastructure Strategy (NCRIS).
A Senate inquiry into oceans and climate change heard this month from scientists concerned programs such as the monitoring of the East Australian Current might be at risk.
"We have had this 70-year history of recording temperature and salinity off Sydney, and some smaller arrays off Narooma, on the South Coast [of NSW], Iain Suthers, an oceanographer at the University of NSW told the inquiry. "If that funding were to cease, we would be left absolutely blind as to the strength and changes of that East Australian Current."

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Climate Change's Mental Health Impacts Need Care Too, Group Says

InsideClimate News - Sabrina Shankman

Often overlooked, the mental part of dealing with extreme weather and other climate impacts is crucial, new report says.
The longterm impacts of climate-related events like the flooding in Louisiana in 2016 are important to address, a new report says. Credit: Getty Images
When a storm driven by climate change forces a family from its home, the impacts don't necessarily disappear once the waters recede and the damage is repaired. Though harder to spot, the impacts on people's mental health can be pervasive and enduring.
That is the thrust of a report released Wednesday by the American Psychological Association, Climate for Health, and ecoAmerica, called "Mental Health and Our Changing Climate: Impacts, Implications, and Guidance."
The report builds on previous work and examines the harm caused by the various manifestations of climate change, from extreme weather and wildfires to heat waves and the general "eco-anxiety" that comes from coping with the enormity of the climate crisis.
"We have this strange situation with climate change in our country that people don't talk about it much, and that means we don't have the opportunity to get prepared for it," said Susan Clayton, one of the report's authors. "That makes it scarier. It seems so amorphous."
The news about climate change can be so frightening, so overwhelming, that instead of shaking people into awareness, it can drive them toward denial. One study cited by the report found that people who received complex information about the threat of climate change felt more helpless and more likely to want to avoid hearing about it in the future.
"Talking about it makes it more manageable and concrete. It can also increase the political will to do something about it," said Clayton.
Climate change's potential impact on mental health isn't universal. Some groups, particularly children and the poor, can be particularly vulnerable.
The report pointed to the response to heat as an example.
By the end of the century, the average American will see between four and eight times as many days above 95 degrees as today, according to estimates cited in the report. Arizona could go from 116 days above 95 degrees to 205 by 2099.
When temperature rises, so does aggression, studies have shown. Heat can also muddle our minds, making it harder to settle disputes without violence.
"It's stressful to be hot, and that leads you to act out," said Clayton. "That has real social justice implications. Who can afford to have air conditioning, and who can't?"
Children are more sensitive to temperatures changes because their sweat glands are not fully developed, making them less able to cool themselves. They are also more prone to dehydration.
Climate impacts can also have longterm effects on their development. The report cited studies that found that children who have experienced a flood or a drought during key developmental periods are shorter, on average, as adults. Pregnant women exposed to heatwaves during their second and third trimesters have a higher chance of going into early labor and tend to have babies with lower birth weights.
And long after the events are over, children are more likely than adults to show severe distress, as well as higher rates of post-traumatic stress disorder.
Mona Sarfaty, the director of the Program for Climate and Health in the Center for Climate Change Communication at George Mason University, who was not a part of the study, said she has encountered this in her work on health care and climate change. After the severe flooding in Louisiana last August, when 30 percent of the state flooded and thousands of people were evacuated, many were fundamentally disoriented, she said. "There were children who became terrified every time it rained subsequently," she said.
With storms, drought and wildfires driven at least in part by climate change spreading to new areas of the country—like the fires in Tennessee and North Carolina last year—more people are being exposed to immediate climate hazards.
Sarfaty is the director of the Medical Society Consortium on Climate & Health, a new group that aims to help the public and policymakers understand how climate change is impacting health. The group represents more than half of the physicians in the country and includes 11 of the nation's leading medical societies.
The consortium recently released a study with similar goals to the mental health study. Both, Sarfaty said, can serve as tools for primary care physicians.
"Every physician needs to be thinking about the mental health impacts of climate change and know the vulnerabilities of their own community so they can help to strengthen people against the impacts," she said.
The mental health report outlined other ways to strengthen people, too.
Encouraging bicycling or walking, or choosing public transit over a car can help, according to the report. Physical activity has a direct connection to mental health, and using public transit fosters a sense of community.
Helping people find ways to prepare for and combat climate change in their own lives—like preparing for extreme events or building  local resilience—can also make it easier to cope with the stress that comes from knowing the world is changing.
"We like to feel secure in our jobs, our finances, our relationships, our homes," said Clayton. "Climate change has a real potential to make us feel insecure in many of those things."

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