• Curbing these 4 pollutants could slow sea level rise

    Andrew Kemp, Yale University

    Sea level rise is swamping coasts; Rodanthe in the Outer Banks of North Carolina is pictured.

    By Becky Oskin
    LiveScience

    Sharp reductions in short-lived airborne pollutants could significantly slow sea level rise before 2100, a new study finds.

    The four pollutants — black carbon, methane, ozone and hydrofluorocarbons — all cycle through the atmosphere more quickly than carbon dioxide, which lasts for centuries in the troposphere, the part of the atmosphere we live in and breathe. Carbon dioxide is the main culprit in Earth's warming temperatures, which impacts sea level rise both by the expansion of water as it warms and by the melting of glacial ice.

    Cutting the air pollutants, which all also act to trap heat in the atmosphere and last anywhere from a week to decade, worldwide by 30 percent to 60 percent over the next several decades would lower predicted sea level rise by 22 percent to 42 percent by 2100, according to the study, published Sunday in the journal Nature Climate Change.

    Sea levels are expected to rise between 7 inches to 6.6 feet (18 centimeters to 2 meters) this century, according to a 2007 assessment by the Intergovernmental Panel on Climate Change. The higher tides will bring more coastal flooding and bigger storm surges, the IPCC report warned.

    Though the four pollutants are known contributors to climate change, policymakers tend to focus on carbon dioxide, the 800-pound-gorilla of global warming, when it comes to reducing emissions. Frustrated at the slow pace of negotiations on cutting carbon dioxide, the research team decided to investigate other ways to slow the planet's warming, according to a statement from the National Center for Atmospheric Research (NCAR) in Boulder, which participated in the research.

    "To avoid potentially dangerous sea level rise, we could cut emissions of short-lived pollutants even if we cannot immediately cut carbon dioxide emissions," NCAR's Aixue Hu, lead study author, said in the statement. "This new research shows that society can significantly reduce the threat to coastal cities if it moves quickly on a handful of pollutants."

    The study models relied on emissions cuts beginning in 2015. Hu and his colleagues tested the effects of lowering atmospheric levels of the four gases and particles by 30 percent to 60 percent over the next several decades, the steepest cuts economists believed possible, the study said.

    Even if these cuts are made, though, carbon dioxide is still the main threat, the authors said.

    "It must be remembered that carbon dioxide is still the most important factor in sea level rise over the long term," Warren Washington, a study co-author at NCAR, said in the statement. "But we can make a real difference in the next several decades by reducing other emissions."

    Email Becky Oskin or follow her @beckyoskin. Follow us @livescience, Facebook and Google+. Original article on LiveScience.com.

    Copyright 2013 LiveScience, a TechMediaNetwork company. All rights reserved. This material may not be published, broadcast, rewritten or redistributed.

  • Ozone overdose confuses pollinators

    By Larry O'Hanlon
    Discovery News

    Ozone isn't just bad for your lungs, it also gets in the way of insects finding their favorite food, say researchers. Ozone, because it reacts readily with aromatic compounds put out by plants, interferes with the come-hither call of the plants to insects.

    “The insects need a threshold amount of gas released by the flower,” said Jose Fuentes of Penn State University. That threshold is pretty low, only about six molecules, for the beetles to detect the plant odor.

    He and meteorology undergraduate John Zenker and University of Virginia researcher T'ai H. Roulston tested beetles inside a Y-shapped tube so that the insect could choose which branch to follow the plant scent. Researchers collected the insects from pumpkin and squash plants then tested them using wild buffalo gourd plants.

    NEWS: Cause Of Odd Arctic Ozone 'Hole' Found

    When they ramped up the ozone, the ability of the beetles to choose the right branch of the tube dropped. When they lowered the ozone again, the beetles were able to detect the gourd plants again. They published their findings in the journal Environmental Research Letters.

    On the face of it, this would seem to be good news for the gourd plant, but not really, Fuentes explained.

    “There's a very very important ecological story there,” said Fuentes. “We have a lot of plants releasing scents to pollinators.” If ozone increases in rural areas, it could impinge on pollinators' abilities to find flowers. “The pollination will decrease. It will affect both native plants and some crops.”

    And since 70 percent of our food comes from plants pollinated by insects, Fuentes said, too much ozone in rural areas could affect our food supply. Urban areas of the United States are seeing lower ozone levels thanks to the Clean Air Act. But rural areas are seeing more ozone as pollution, because the intense industrialization of Asia blows across the Pacific Ocean, Fuentes said.

    NEWS: Antarctic Ozone Hole 2nd Smallest In 20 Years

    Another potential complication for plants is that some are known to protect themselves with scents. When under attack by a plant-eating insect, some plants will release special odors to attract predatory insects that will eat the herbivores. But if ozone is interfering with this distress signal, the plants lose one of their most powerful defenses.

    “I think this study is very important with regards to how human activities can affect ecological systems,” said Paul Shepson, who directs a atmospheric chemistry lab at Purdue University. “It's an area of impact that not a lot of people are looking at.”

    On the other hand, Shepson point out, not all ozone is bad. At lower concentrations, it's essential for breaking down pollutants, even those produced by swamps and other natural features, that can then be rained out of the atmosphere.

    “If there wasn't this mechanism for the atmosphere to clean itself, we'd be dead in months, or would have evolved very differently,” said Shepson.

  • Cause of odd Arctic ozone 'hole' found

    NASA/Goddard

    Maps of ozone concentrations over the Arctic on March 19, 2010 (left) and the same day in 2011 (right), measured by the Ozone Monitoring Instrument on NASA's Aura satellite.

    By Stephanie Pappas, LiveScience

    Cold temperatures, chlorine and a stagnant atmosphere caused a thinning in the ozone layer over the Arctic in 2011, a new NASA study finds.

    This ozone loss is not the more famous ozone hole, found seasonally over Antarctica, which has been shrinking since the phase-out of chlorofluorocarbons, or CFCs, that interact with ozone molecules in the atmosphere. These ozone molecules are made of three oxygen atoms bound together. Their high concentration in the stratosphere about 12 miles to 19 miles above the Earth's surface blocks harmful ultraviolet light from the sun.

    Arctic ozone depletion is typically not as severe as that in the Antarctic. Over the South Pole, the sun barely or never sets around Christmas, creating a confluence of sunlight and cold in the atmosphere. Under these conditions, chlorine from CFCs eats away at ozone molecules. [See Ozone Animation]

    Arctic ozone
    Up north, however, the sun reappears in the sky in the spring as temperatures start to warm, so the conditions aren't as favorable for ozone depletion. But in 2011, the ozone concentration in the late winter Arctic was about 20 percent lower than average. [North vs. South Pole: 10 Wild Differences]

    "You can safely say that 2011 was very atypical: In over 30 years of satellite records, we hadn't seen any time where it was this cold for this long," study researcher Susan Strahan, an atmospheric scientist at NASA Goddard Space Flight Center, said in a statement.

    Using atmospheric simulations, Strahan and her colleagues found that a mix of cold temperatures, chlorine and an unusually strong Arctic vortex caused the odd thinning. The Arctic vortex is a region of fast-blowing circular winds that get stronger each fall, creating an eddy of chilled air around the pole.

    In 2011, the atmosphere was unusually quiet, allowing the Arctic vortex to remain strong well into the spring, after it usually breaks up. The reappearance of the sun in March while it was still especially cold created the conditions that led to the ozone thinning, the researchers report in the Journal of Geophysical Research - Atmospheres.

    "Arctic ozone levels were possibly the lowest ever recorded, but they were still significantly higher than the Antarctic's," Strahan said. "There was about half as much ozone loss as in the Antarctic," and the levels remained above the threshold for calling the ozone loss an actual "hole," Strahan added. 

    Future outlook
    Strahan and her team calculate that two-thirds of the thinning was caused by a combination of chlorine pollution and extreme cold. The remaining third was caused by the oddly quiet atmosphere, which prevented ozone molecules from elsewhere from moving in to fill the gap.

    The ozone layer over the Arctic returned to normal in April 2011. It's unlikely that such thinning will become a reoccurring problem, because the meteorological conditions were so odd, Strahan said. Not only that, but CFC levels in the atmosphere are still declining.

    "If 30 years from now we had the same meteorological conditions again, there would actually be less chlorine in the atmosphere, so the ozone depletion probably wouldn't be as severe," she said.

    Follow Stephanie Pappas @sipappas. Follow LiveScience on Twitter @livescience, Facebook or Google+. Original article on LiveScience.com.

    Copyright 2013 LiveScience, a TechMediaNetwork company. All rights reserved. This material may not be published, broadcast, rewritten or redistributed.

     

  • NASA drone to probe loss of Earth's protective ozone

    J. Zavaleta / NASA

    This is a NASA Global Hawk being loaded with monitoring equipment for the ATTREX mission.

    By Becky Oskin
    Our Amazing Planet

    Water may play a critical role in controlling the ozone gas high up in Earth's atmosphere that can act as a greenhouse gas or protect living things on the surface below from the sun's harmful ultraviolet rays, depending on where in the atmosphere it is found.

    To better understand how water vapor and ozone interact, NASA plans to send a remote-controlled plane laden with monitoring equipment into the stratosphere — the layer of the atmosphere where protective ozone is found — above the tropics.

    The drone will crisscross the tropopause, the boundary between the troposphere (the layer of the atmosphere we breathe and where most weather occurs), and the stratosphere. The boundary is a fluid layer whose thickness can change and depends on the latitude it is located over but that is generally found about 8 to 11 miles (5 to 7 kilometers) above Earth's surface.

    In the middle reaches of the troposphere, ozone is a greenhouse gas, trapping heat and contributing to smog. But high in the troposphere and the stratosphere, the familiar ozone layer protects the planet from harmful UV radiation.

    When storms punch water vapor through the tropopause, into the stratosphere, scientists suspect chemical reactions between water and free radicals such as chlorine may zap and destroy the protective ozone. The NASA experiment will sample this layer near the equator off the coast of Central America where tall thunderstorms often occur.

    The flights, which start this month, are the first of a multiyear campaign to study how changes in water vapor in the stratosphere can affect global climate. The Airborne Tropical Tropopause Experiment (ATTREX) relies on a Global Hawk drone, which can cruise for 30 hours from its home at Edwards Air Force Base in California. The aircraft are also used by the U.S. Air Force and Navy.

    Predictions of stratospheric humidity changes are uncertain because of gaps in the understanding of the physical processes occurring in the tropical tropopause layer, NASA said in a statement.

    "The ATTREX payload will provide unprecedented measurements of the tropical tropopause," Eric Jensen, ATTREX principal investigator, said in a statement. "This is our first opportunity to sample the tropopause region during winter in the Northern Hemisphere when it is coldest and extremely dry air enters the stratosphere."

    Reach Becky Oskin at boskin@techmedianetwork.com. Follow her on Twitter @beckyoskin. Follow OurAmazingPlanet on Twitter @OAPlanet. We're also on Facebook and Google+.