Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:


Researchers Shows Emissions From Forests Influence Very First Stage of Cloud Formation


Research from CLOUD Experiment at CERN, Which Includes Carnegie Mellon's Neil Donahue, Contributes to Better Understanding of Connection Between Clouds and Climate

Clouds play a critical role in Earth's climate. Clouds also are the largest source of uncertainty in present climate models, according to the latest report of the Intergovernmental Panel on Climate Change. Much of the uncertainty surrounding clouds' effect on climate stems from the complexity of cloud formation.

New research from scientists at the CLOUD (Cosmics Leaving OUtdoor Droplets) experiment at CERN, including Carnegie Mellon University's Neil Donahue, sheds light on new-particle formation — the very first step of cloud formation and a critical component of climate models. The findings, published in the May 16 issue of Science, closely match observations in the atmosphere and can help make climate prediction models more accurate.

Cloud droplets form when water vapor in the atmosphere condenses onto tiny particles. These particles are emitted directly from natural sources or human activity, or they form from precursors emitted originally as gaseous pollutants. The transformation of gas molecules into clusters and then into particles, a process called nucleation, produces more than half of the particles that seed cloud formation around the world today. But the mechanisms underlying nucleation remain unclear. Although scientists have observed that the nucleation process nearly always involves sulfuric acid, sulfuric acid concentrations aren't high enough to explain the rate of new particle formation that occurs in the atmosphere. This new study uncovers an indispensable ingredient to the long sought-after cloud formation recipe — highly oxidized organic compounds.

"Our measurements connect oxidized organics directly, and in detail, with the very first steps of new particle formation and growth," said Donahue, professor of chemistry, chemical engineering, engineering and public policy, and director of CMU's Steinbrenner Institute for Environmental Education and Research. "We had no idea a year ago that this chemistry was happening. There's a whole branch of oxidation chemistry that we didn't really understand. It's an exciting time."

The air we breathe is chock-full of organic compounds, tiny liquid or solid particles that come from hundreds of sources including trees, volcanoes, cars, trucks and wood fires. Once they enter the atmosphere, these so-called organics start to change. In research published in the Proceedings of the National Academy of Sciences in 2012, Donahue and colleagues showed conclusively that organic molecules given off by pine trees, called alpha-pinene, are chemically transformed multiple times in the highly oxidizing environment of the atmosphere. Additionally, other research, including from Donahue's lab, has suggested that such oxidized organics might take part in nucleation — both in new particle formation and in their subsequent growth. Donahue and an international team of researchers with the CLOUD experiment at CERN set out to test that hypothesis.

The CLOUD project at CERN is a unique facility that allows scientists to reproduce a typical atmospheric setting inside of an essentially contaminant-free, stainless steel chamber. By performing experiments in the precisely controlled environment of the CLOUD chamber, the project's scientists can change the concentrations of chemicals involved in nucleation and then measure the rate at which new particles are created with extreme precision.

In the current work, the team filled the chamber with sulfur dioxide and pinnanediol (an oxidation product of alpha-pinene) and then generated hydroxyl radicals (the dominant oxidant in Earth's atmosphere). Then they watched the oxidation chemistry unfold. Using very high-resolution mass spectrometry, the scientists were able to observe particles growing from single, gaseous molecules to clusters of up to 10 molecules stuck together, as they grew molecule by molecule.

"It turns out that sulfuric acid and these oxidized organic compounds are unusually attracted to each other. This remarkably strong association may be a big part of why organics are really drawn to sulfuric acid under modern polluted conditions," Donahue said.

After confirming that oxidized organics are involved in the formation and growth of particles under atmospheric conditions, the scientists incorporated their findings into a global particle formation model. The fine-tuned model not only predicted nucleation rates more accurately but also predicted the increases and decreases of nucleation observed in field experiments over the course of a year, especially for measurements near forests. This latter test is a strong confirmation of the fundamental role of emissions from forests in the very first stage of cloud formation, and that the new work may have succeeded in modeling that influence.


New research from scientists at the CLOUD (Cosmics Leaving OUtdoor Droplets) experiment at CERN, including Carnegie Mellon's Neil Donahue, is contributing to a better understanding of the connection between clouds and climate.

Jocelyn Duffy | Eurek Alert!
Further information:

Further reports about: CERN Cloud acid atmosphere concentrations formation nucleation particles sulfuric

More articles from Earth Sciences:

nachricht Rapid plankton growth in ocean seen as sign of carbon dioxide loading
27.11.2015 | Johns Hopkins University

nachricht Revealing glacier flow with animated satellite images
26.11.2015 | European Geosciences Union

All articles from Earth Sciences >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Climate study finds evidence of global shift in the 1980s

Planet Earth experienced a global climate shift in the late 1980s on an unprecedented scale, fuelled by anthropogenic warming and a volcanic eruption, according to new research published this week.

Scientists say that a major step change, or ‘regime shift’, in the Earth’s biophysical systems, from the upper atmosphere to the depths of the ocean and from...

Im Focus: Innovative Photovoltaics – from the Lab to the Façade

Fraunhofer ISE Demonstrates New Cell and Module Technologies on its Outer Building Façade

The Fraunhofer Institute for Solar Energy Systems ISE has installed 70 photovoltaic modules on the outer façade of one of its lab buildings. The modules were...

Im Focus: Lactate for Brain Energy

Nerve cells cover their high energy demand with glucose and lactate. Scientists of the University of Zurich now provide new support for this. They show for the first time in the intact mouse brain evidence for an exchange of lactate between different brain cells. With this study they were able to confirm a 20-year old hypothesis.

In comparison to other organs, the human brain has the highest energy requirements. The supply of energy for nerve cells and the particular role of lactic acid...

Im Focus: Laser process simulation available as app for first time

In laser material processing, the simulation of processes has made great strides over the past few years. Today, the software can predict relatively well what will happen on the workpiece. Unfortunately, it is also highly complex and requires a lot of computing time. Thanks to clever simplification, experts from Fraunhofer ILT are now able to offer the first-ever simulation software that calculates processes in real time and also runs on tablet computers and smartphones. The fast software enables users to do without expensive experiments and to find optimum process parameters even more effectively.

Before now, the reliable simulation of laser processes was a job for experts. Armed with sophisticated software packages and after many hours on computer...

Im Focus: Quantum Simulation: A Better Understanding of Magnetism

Heidelberg physicists use ultracold atoms to imitate the behaviour of electrons in a solid

Researchers at Heidelberg University have devised a new way to study the phenomenon of magnetism. Using ultracold atoms at near absolute zero, they prepared a...

All Focus news of the innovation-report >>>



Event News

Fraunhofer’s Urban Futures Conference: 2 days in the city of the future

25.11.2015 | Event News

Gluten oder nicht Gluten? Überempfindlichkeit auf Weizen kann unterschiedliche Ursachen haben

17.11.2015 | Event News

Art Collection Deutsche Börse zeigt Ausstellung „Traces of Disorder“

21.10.2015 | Event News

Latest News

Siemens to supply 126 megawatts to onshore wind power plants in Scotland

27.11.2015 | Press release

Two decades of training students and experts in tracking infectious disease

27.11.2015 | Life Sciences

Coming to a monitor near you: A defect-free, molecule-thick film

27.11.2015 | Materials Sciences

More VideoLinks >>>