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.
“Recent anthropogenic increases in SO2 from Asia have minimal impact on stratospheric
R. R. Neely III: Department of Atmospheric and Oceanic Sciences, University of Colorado,
Boulder, Colorado, USA; NOAA, Earth System Research Laboratory, Boulder, Colorado, USA;
and Cooperative Institute for Research in Environmental Sciences, Boulder, Colorado, USA;
O. B. Toon: Department of Atmospheric and Oceanic Sciences, University of Colorado, Boulder,
Colorado, USA; and Laboratory for Atmospheric and Space Physics, University of Colorado,
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
Cooperative Institute for Research in Environmental Sciences, Boulder, Colorado, USA;
J. M. English, M. J. Mills, and C.G. Bardeen: Earth System Laboratory, National Center for
Atmospheric Research, Boulder, Colorado, USA;
K. H. Rosenlof and J. S. Daniel: NOAA, Earth System Research Laboratory, Boulder, Colorado,
J. P. Thayer: Department of Aerospace Engineering Sciences, University of Colorado, Boulder,
Contact information for the authors:
Ryan Neely: Phone: +1 (336) 302-4244, Email: Ryan.Neely@colorado.edu
Brian Toon: Phone: +1 (303) 492-1534, Email: Brian.Toon@colorado.edu
Kate Ramsayer | Source: American Geophysical Union
Further information: www.agu.org
Further Reports about: American Geophysical Union > atmosphere > Atmospheric > Atmospheric Research > chemical reaction > dioxide emissions > Earth's magnetic field > Earth’s surface > environmental risk > Environmental Sciences > gas emission > greenhouse gas > greenhouse gas emission > Mobile phone > NASA > Science TV > volcanic eruptions > volcanic gas
More articles from Earth Sciences:
Tracking the Earth’s Mantle
24.05.2013 | Syracuse University
Strong earthquake at exceptional depth
24.05.2013 | Helmholtz-Zentrum Potsdam - Deutsches GeoForschungsZentrum GFZ
This morning at 05:45 CEST, the earth trembled beneath the Okhotsk Sea in the Pacific Northwest. The quake, with a magnitude of 8.2, took place at an exceptional depth of 605 kilometers.
Because of the great depth of the earthquake a tsunami is not expected and there should also be no major damage due to shaking.
Professor Frederik Tilmann of the GFZ German Research Centre for Geosciences: "The epicenter is exceptionally deep, far below the earth's crust in the mantle. Such strong ...
The Ring Nebula's distinctive shape makes it a popular illustration for astronomy books. But new observations by NASA's Hubble Space Telescope of the glowing gas shroud around an old, dying, sun-like star reveal a new twist.
"The nebula is not like a bagel, but rather, it's like a jelly doughnut, because it's filled with material in the middle," said C. Robert O'Dell of Vanderbilt University in Nashville, Tenn.
He leads a research team that used Hubble and several ground-based telescopes to obtain the best view yet of ...
New indicator molecules visualise the activation of auto-aggressive T cells in the body as never before
Biological processes are generally based on events at the molecular and cellular level. To understand what happens in the course of infections, diseases or normal bodily functions, scientists would need to examine individual cells and their activity directly in the tissue.
The development of new microscopes and fluorescent dyes in ...
A fried breakfast food popular in Spain provided the inspiration for the development of doughnut-shaped droplets that may provide scientists with a new approach for studying fundamental issues in physics, mathematics and materials.
The doughnut-shaped droplets, a shape known as toroidal, are formed from two dissimilar liquids using a simple rotating stage and an injection needle. About a millimeter in overall size, the droplets are produced individually, their shapes maintained by a surrounding springy material made of polymers.
Droplets in this toroidal shape made ...
Frauhofer FEP will present a novel roll-to-roll manufacturing process for high-barriers and functional films for flexible displays at the SID DisplayWeek 2013 in Vancouver – the International showcase for the Display Industry.
Displays that are flexible and paper thin at the same time?! What might still seem like science fiction will be a major topic at the SID Display Week 2013 that currently takes place in Vancouver in Canada.
High manufacturing cost and a short lifetime are still a major obstacle on ...
24.05.2013 | Life Sciences
24.05.2013 | Ecology, The Environment and Conservation
24.05.2013 | Physics and Astronomy
17.05.2013 | Event News
15.05.2013 | Event News
08.05.2013 | Event News