ACOM scientist Simone Tilmes was quoted in Live Science about a proposal to use salt in the upper troposphere to increase the atmosphere's reflectivity and thereby cool the earth. Unlike some other aerosols, sodium chloride (table salt) is not harmful to the earth's ozone layer. Tilmes cautions that salt often includes reactive iodine, an element that could also play a role in atmospheric chemistry.

April 6, 2018

In a surprising study, scientists say everyday chemicals now rival cars as a source of air pollution. Chris Mooney at The Washington Post reports that "the nature of air pollution is changing dramatically as cars become cleaner — leaving personal-care products, paints, indoor cleaners and other chemical-containing agents as an increasingly dominant source of key emissions." As emissions from the transportation sector decrease, the gases emitted by household products and activities have become more significant.

The published paper "Volatile chemical products emerging as largest petrochemical source of urban organic emissions" includes contributions by ACOM and CIRES scientist Julia Lee-Taylor.
Citation: Science 16 Feb 2018: Vol. 359, Issue 6377, pp. 760-764. DOI: 10.1126/science.aaq052

February 15, 2018

A comprehensive new air quality report for the state of Colorado quantifies the sources of summertime ozone in Denver and the northern Front Range, revealing the extent to which motor vehicles and oil and gas operations are the two largest local contributors to the pollutant. The report was authored by ACOM scientists Gabriele Pfister, Frank Flocke, Rebecca Hornbrook, and and John Orlando. The Boulder Daily Camera also covered the FRAPPÉ and DISCOVER-AQ 2014 final report on October 30, 2017: Vehicles, oil and gas top sources of Front Range ozone, NCAR study shows.

Tremendous amounts of soot, lofted into the air from global wildfires following a massive asteroid strike 66 million years ago, would have plunged Earth into darkness for nearly two years, new research finds. This would have shut down photosynthesis, drastically cooled the planet, and contributed to the mass extinction that marked the end of the age of dinosaurs.

The news article by NCAR science writer Laura Snider highlights recent work by ACOM scientists Charles Bardeen, Rolando Garcia, and Andrew Conley.

Measurements of carbon dioxide from the MOPITT satellite instrument have been validated using the NDACC network of ground-based measurements. ACOM scientist Rebecca Buchholz and colleagues reported on their study of MOPITT version 6 retrievals using total column CO measurements from ground-based remote-sensing Fourier transform infrared spectrometers (FTSs). MOPITT generally shows a small bias with respect to the ground-based measurements. The ground stations are located worldwide at latitudes ranging from 80° N to 78° S, and are maintained by the Network for the Detection of Atmospheric Composition Change (NDACC).

Reference:

Buchholz, R. R., Deeter, M. N., Worden, H. M., Gille, J., Edwards, D. P., Hannigan, J. W., Jones, N. B., Paton-Walsh, C., Griffith, D. W. T., Smale, D., Robinson, J., Strong, K., Conway, S., Sussmann, R., Hase, F., Blumenstock, T., Mahieu, E., and Langerock, B.: Validation of MOPITT carbon monoxide using ground-based Fourier transform infrared spectrometer data from NDACC, Atmos. Meas. Tech., 10, 1927-1956, https://doi.org/10.5194/amt-10-1927-2017, 2017.

About half of atmospheric carbon monoxide (CO) is from direct (CO) emissions that are due to incomplete combustion and are related to both natural (e.g. wildfires) and anthropogenic activities. The remainder of CO in the atmosphere is produced from the chemical oxidation of hydrocarbons, mainly from biogenic sources and methane (CH₄). Since most of the hydrocarbons, CO, and CH₄ in the atmosphere are oxidized by the hydroxyl radical (OH), the associated chemical lifetimes of these species are strongly coupled with OH. For example, a reduction in CO emissions leads to more OH and therefore a shorter CH₄ lifetime, assuming CH₄ emissions are the same. This means that long-lived greenhouse gases such as CH₄ are linked with short-lived pollutants related to air quality. We use the NCAR coupled chemistry-climate model of the Community Earth System Model (or CESM http://www.cesm.ucar.edu/) Community Atmospheric Model with Chemistry (or CAM-Chem, https://www2.acom.ucar.edu/gcm/cam-chem ) to investigate the coupled nature of our chemical system through a decadal chemical reanalysis experiments. We assimilate weather observations and satellite-based measurements of CO from The Measurement of the Pollution in the Troposphere (MOPITT, http://www2.acom.ucar.edu/mopitt) across the recent decade (2002-2013) using the Data Assimilation Research Testbed (DART, http://www.image.ucar.edu/DAReS/DART/).

Based on these experiments, we confirm previous reports of decreasing trends in global CO burden that is mainly attributed to the reduction of CO emissions from anthropogenic sources.  However, the impact of this reduction in CO on CH₄ chemical loss is not clear at this juncture. The rate of CH₄ loss is dependent upon CH₄ abundance and OH concentrations. It is also evident from atmospheric CH₄ observations that the increase in CH₄ sources leads to a positive growth rate of CH₄ abundance over the recent decade and therefore leading to a positive trend in the absolute magnitude of CH₄ chemical loss. As a consequence, this increase in CH₄ loss leads to a positive trend in the chemical production of CO (secondary CO). From our reanalysis, we find that the other sources of secondary CO from biogenic sources (represented here as isoprene which is most important hydrocarbon emitted from vegetation), exhibits no significant trend.  Since the chemical lifetime of CH₄ is inversely proportional to OH (where its main sink is CO), we infer from our analysis that during this period of long-term decline of CO abundance (mainly from changes in anthropogenic CO emissions), it is likely that we observed a reduced rate of increase in CH₄ abundance and loss than in a scenario where CO emissions are the same. These results show the potential cobenefits of reducing both CO and CH₄ emissions to mitigate climate and air pollution impacts.

Top panel: Monthly anomalies of globally integrated emissions of isoprene (Tg Isoprene/Month) as well as
tropospheric columns of chemical fluxes (in Tg(molecule)/Month) estimated from the NCAR-MOPITT Reanalysis

Reference:  Gaubert, B., Arellano, A. F., Barré, J., Worden, H. M., Emmons, L. K., Tilmes, S., Buchholz, R. R., Vitt, F., Raeder, K., Collins, N., Anderson, J. L., Wiedinmyer, C., Martinez Alonso, S., Edwards, D. P., Andreae, M. O., Hannigan, J. W., Petri, C., Strong, K., and Jones, N.: Toward a chemical reanalysis in a coupled chemistry-climate model: An evaluation of MOPITT CO assimilation and its impact on tropospheric composition, J. Geophys. Res.-Atmos., doi:10.1002/2016JD024863, http://dx.doi.org/10.1002/2016JD024863, 2016JD024863, 2016.

With world leaders agreeing to try to limit the increase in global temperatures, scientists at the National Center for Atmospheric Research (NCAR) are taking a look at whether geoengineering the climate could counter enough warming to help meet that goal. "One thing that surprised me about this study is how much geoengineering it would take to stay within 2 degrees if we don't start reducing greenhouse gases soon," said ACOM scientist Simone Tilmes, the lead author.

Susan Solomon at MIT, along with ACOM scientists Doug Kinnison and Michael Mills, have identified the “first fingerprints of healing” of the Antarctic ozone layer, published on June 30, 2016 in the journal Science. The research was covered by BBC Science.

The research team found that the September ozone hole has shrunk by more than 4 million square kilometers — about half the area of the contiguous United States — since 2000, when ozone depletion was at its peak. They also showed for the first time that this recovery has slowed somewhat at times, due to the effects of volcanic eruptions from year to year. Overall, however, the ozone hole appears to be on a healing path.

The other paper co-authors are Diane Ivy of MIT, Ryan Neely of the University of Leeds, and Anja Schmidt of the University of Leeds.

Discovery News: A strike by a medium-size asteroid in a forested region could change the Earth’s climate to ice-age like conditions with effects lasting for up to 10 years. Airborne soot and dust aerosols would decrease the amount of sunlight reaching the Earth’s surface, which would cause significant surface cooling, reduce precipitation and could threaten global food supplies, says ACOM's Chuck Bardeen. The impact study was carried out using the WACCM atmospheric model.

A research paper co-authored by ACOM scientist Dan Marsh was featured in Eos. The paper describes how WACCM version 4 produces a stronger vertical circulation in the earth's atmosphere, bringing NO and NO₂ down into the stratosphere over Antarctica and destroying ozone there. WACCM4 provides the basis for new studies that may increase our understanding of the sun’s impact on climate. The original paper "Simulated solar cycle effects on the middle atmosphere: WACCM3 Versus WACCM4" was published in Journal of Advances in Modeling Earth System (June 2015).

October 21, 2015 | ACOM scientists Jerome Barre, David Edwards, and Helen Worden have demonstrated how new types of satellite data could improve how agencies monitor and forecast air quality, both globally and by region. The new satellite observations would significantly improve air pollution forecasts.

The scientists used computer simulations to test a method that combines analysis of chemistry-climate model output with the kind of data that could be obtained from a planned fleet of geostationary satellites, each of which would view a large area of Earth on a continuous basis from high orbit.

"We think the new perspective made possible by geostationary sensors would provide data that is useful for everyday air quality forecasting, as well as for early warnings about extreme events, like the effects of wildfires," said Helen Worden.

Read more at UCAR AtmosNews...

A scientific paper by Chester Gardner, Alan Liu, ACD Scientist Dan Marsh, Wuhu Feng, and J. M. C. Plane has been selected by the American Geophysical Union as an "AGU Research Spotlight." Inferring the global cosmic dust in flux to the Earth’s atmosphere from lidar observations of the vertical flux of mesospheric Na (2014) was published in the Journal of Geophysical Research: Space Physics. The research studied the meteoric debris that enters the Earth's atmosphere and is eventually transported to the surface.

Marty Coniglio chats with ACD's Frank Flocke about the NCAR planes testing ozone pollution (July 25). The news video is 5 minutes long and includes interior shots of the instrumentation used aboard the research aircraft.

The Boulder Daily Camera reports:
It sounds like a delectable dessert; but in fact, ACD's FRAPPÉ field campaign is an ambitious effort to gather thorough data on all the pollutants that appear in the atmosphere over the Front Range during the summer months and prevent the metro area from meeting federal air quality standards. "Something this comprehensive, such a major campaign, has not happened in the Front Range before," said Gabriele Pfister, an atmospheric scientist for NCAR. She and NCAR's Frank Flocke are the study's two principal investigators.

The Baltimore Sun reports the ongoing CONTRAST field campaign taking place in Guam. Flights by three research aircraft allow scientists from NCAR's Atmospheric Chemistry Division, the University of Miami, and the University of Maryland to study the effects of tropical thunderstorms on the atmosphere, as towering cumulus clouds loft surface air high over the warm Pacific ocean. (January 24, 2014)

Tim McDonnell and James West of Climate Desk were invited to fly along with the NASA DC-8 on a SEAC4RS mission to investigate and measure clouds. The resulting video published at Mother Jones magazine shows the on-board equipment used within the cramped space of the cabin. Scientists in flight keep busy monitoring levels of aerosols, solar radiation, CO₂, biogenic emissions, and other atmospheric chemicals. (published September 4, 2014)