The research indicates also that industrial sulfur dioxide emissions from India and China, which were suspected of tempering the warming, did not play a significant role, said lead study author Ryan Neely, who led the research as part of his University of Colorado Boulder doctoral thesis.
Small amounts of sulfur dioxide emissions from Earth’s surface eventually rise to 19 to 32 kilometers (12 to 20 miles) into the stratosphere, where chemical reactions create a mist, or aerosol, of sulfuric acid droplets and water droplets that reflects sunlight back to space, cooling the planet.
Neely said previous observations suggest that increases in stratospheric aerosols since 2000 have counterbalanced as much as 25 percent of the warming scientists blame on human greenhouse gas emissions. “This new study indicates it is emissions from small to moderate volcanoes that have been slowing the warming of the planet,” said Neely, a researcher at the Cooperative Institute for Research in Environmental Sciences, a joint venture of CU and the National Oceanic and Atmospheric Administration.
A paper on the subject has been accepted for publication in Geophysical Research Letters, a journal of the American Geophysical Union. The new project was undertaken in part to resolve conflicting results of two recent studies on the origins of the sulfur dioxide in the stratosphere, including a 2009 study led by the late David Hoffman of NOAA, which indicated aerosol increases in the stratosphere may have come from rising emissions of sulfur dioxide from India and China.
In contrast, a 2011 study led by Jean Paul Vernier of NASA’s Langley Research Center in Hampton, Va. -- who also provided essential observation data for the new GRL study -- showed moderate volcanic eruptions play a role in increasing particulates in the stratosphere, Neely said. The new study relies on long-term measurements of changes in the stratospheric aerosol layer’s “optical depth,” which is a measure of transparency, Neely said. Since 2000, the optical depth in the stratospheric aerosol layer has increased by about 4 percent to 7 percent, meaning it is slightly more opaque now than in previous years.
“The biggest implication here is that scientists need to pay more attention to small and moderate volcanic eruptions when trying to understand changes in Earth’s climate,” said Brian Toon of CU-Boulder’s Atmospheric and Oceanic Sciences Department, a co-author of the new study. “But overall theses eruptions are not going to counter the greenhouse effect. Emissions of volcanic gases go up and down, helping to cool or heat the planet, while greenhouse gas emissions from human activity just continue to go up.”
The key to the new results was the combined use of two sophisticated computer models, including the Whole Atmosphere Community Climate Model, or WACCM, Version 3, developed by the National Center for Atmospheric Research in Boulder and is widely used around the world by scientists to study the atmosphere. The team coupled WACCM with a second model, the Community Aerosol and Radiation Model for Atmosphere, or CARMA, which allows researchers to calculate properties of specific aerosols and which has been under development by a team led by Toon for the past several decades.
Neely said the team used the Janus supercomputer on campus to conduct seven computer “runs,” each simulating 10 years of atmospheric activity tied to both coal-burning activities in Asia and to emissions by volcanoes around the world. Each run took about a week of computer time using 192 processors, allowing the team to separate coal-burning pollution in Asia from aerosol contributions from moderate, global volcanic eruptions. The project would have taken a single computer processor roughly 25 years to complete, said Neely.
The scientists said 10-year climate data sets like the one gathered for the new study are not long enough to determine climate change trends. “This paper addresses a question of immediate relevance to our understanding of the human impact on climate,” said Neely. “It should interest those examining the sources of decadal climate variability, the global impact of local pollution and the role of volcanoes.” While small and moderate volcanoes mask some of the human-caused warming of the planet, larger volcanoes can have a much bigger effect, Toon said.
When Mount Pinatubo in the Philippines erupted in 1991, it emitted millions of tons of sulfur dioxide into the atmosphere that cooled the Earth slightly for the next several years. The research for the new study was funded in part through a NOAA/ ESRL-CIRES Graduate Fellowship to Neely. The NSF and NASA also provided funding for the research project. The Janus supercomputer is supported by NSF and CU-Boulder and is a joint effort of CU-Boulder, CU-Denver and NCAR.Title:
and Cooperative Institute for Research in Environmental Sciences, Boulder, Colorado, USA;O. B. Toon: Department of Atmospheric and Oceanic Sciences, University of Colorado, Boulder,
Boulder, Colorado, USA;S. Solomon: Department of Earth, Atmospheric and Planetary Sciences, Massachusetts Institute
of Technology, Cambridge, Massachusetts, USA;J. P. Vernier: Science Systems and Applications, Inc., Hampton, Virginia, USA; and NASA,
Langley Research Center, Hampton, Virginia, USA;C. Alvarez: NOAA, Earth System Research Laboratory, Boulder, Colorado, USA; and
Atmospheric Research, Boulder, Colorado, USA;K. H. Rosenlof and J. S. Daniel: NOAA, Earth System Research Laboratory, Boulder, Colorado,
USA;J. P. Thayer: Department of Aerospace Engineering Sciences, University of Colorado, Boulder,
Colorado, USA.Contact information for the authors:
Kate Ramsayer | American Geophysical Union
Further reports about: > American Geophysical Union > Atmospheric > Atmospheric Research > Earth's magnetic field > Earth’s surface > Environmental Sciences > Mobile phone > NASA > Science TV > atmosphere > chemical reaction > dioxide emissions > environmental risk > gas emission > greenhouse gas > greenhouse gas emission > volcanic eruptions > volcanic gas
How do megacities impact coastal seas? Searching for evidence in Chinese marginal seas
11.12.2017 | Leibniz-Institut für Ostseeforschung Warnemünde
What makes corals sick?
11.12.2017 | Leibniz-Zentrum für Marine Tropenforschung (ZMT)
Tiny pores at a cell's entryway act as miniature bouncers, letting in some electrically charged atoms--ions--but blocking others. Operating as exquisitely sensitive filters, these "ion channels" play a critical role in biological functions such as muscle contraction and the firing of brain cells.
To rapidly transport the right ions through the cell membrane, the tiny channels rely on a complex interplay between the ions and surrounding molecules,...
The miniaturization of the current technology of storage media is hindered by fundamental limits of quantum mechanics. A new approach consists in using so-called spin-crossover molecules as the smallest possible storage unit. Similar to normal hard drives, these special molecules can save information via their magnetic state. A research team from Kiel University has now managed to successfully place a new class of spin-crossover molecules onto a surface and to improve the molecule’s storage capacity. The storage density of conventional hard drives could therefore theoretically be increased by more than one hundred fold. The study has been published in the scientific journal Nano Letters.
Over the past few years, the building blocks of storage media have gotten ever smaller. But further miniaturization of the current technology is hindered by...
With innovative experiments, researchers at the Helmholtz-Zentrums Geesthacht and the Technical University Hamburg unravel why tiny metallic structures are extremely strong
Light-weight and simultaneously strong – porous metallic nanomaterials promise interesting applications as, for instance, for future aeroplanes with enhanced...
An interdisciplinary group of researchers interfaced individual bacteria with a computer to build a hybrid bio-digital circuit - Study published in Nature Communications
Scientists at the Institute of Science and Technology Austria (IST Austria) have managed to control the behavior of individual bacteria by connecting them to a...
Physicists in the Laboratory for Attosecond Physics (run jointly by LMU Munich and the Max Planck Institute for Quantum Optics) have developed an attosecond electron microscope that allows them to visualize the dispersion of light in time and space, and observe the motions of electrons in atoms.
The most basic of all physical interactions in nature is that between light and matter. This interaction takes place in attosecond times (i.e. billionths of a...
11.12.2017 | Event News
08.12.2017 | Event News
07.12.2017 | Event News
11.12.2017 | Physics and Astronomy
11.12.2017 | Earth Sciences
11.12.2017 | Information Technology