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Source article

ACP

Published By

Dr. Dick van der Wateren

Tags

Greenhouse Gases, Aerosols, Climate Change, Aerosol-cloud interaction


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Climate sensitivity greater than previously believed

03.01.2012, Age: 2533 days

Atmospheric chemists from Sweden, Germany and the US reveal how plant emissions into the atmosphere mask the effect of human-induced greenhouse warming. Plants emit substances that produce aerosols that may have a cooling effect in one area while amplifying greenhouse warming elsewhere. When temperature rises they will do so at higher rates.

The team, led by the Department of Chemistry at the University of Gothenburg, Sweden, published their findings in a recent issue of the open-access journal Atmospheric Chemistry and Physics. The research was part of the PhD thesis of Kent Salo, first author of the article in ACP.

From the website of the University of Gothenburg:

"Many of the particles in the atmosphere are produced by the natural world, and it is possible that plants have in recent decades reduced the effects of the greenhouse gases to which human activity has given rise. One consequence of this is that the climate may be more sensitive to emissions caused by human activity than we have previously believed. Scientists at the University of Gothenburg have collected new data that may lead to better climate models."

See also "‘No, climate sensitivity is not smaller, it is higher than we thought' - because organic aerosol feedbacks mask warming" at bits of science.

Abstract

The aim of this study was to investigate oxidation of SOA formed from ozonolysis of α-pinene and limonene by hydroxyl radicals. This paper focuses on changes of particle volatility, using a Volatility Tandem DMA (VTDMA) set-up, in order to explain and elucidate the mechanism behind atmospheric ageing of the organic aerosol. The experiments were conducted at the AIDA chamber facility of Karlsruhe Institute of Technology (KIT) in Karlsruhe and at the SAPHIR chamber of Forchungzentrum Jülich (FZJ) in Jülich. A fresh SOA was produced from ozonolysis of α-pinene or limonene and then aged by enhanced OH exposure. As an OH radical source in the AIDA-chamber the ozonolysis of tetramethylethylene (TME) was used while in the SAPHIR-chamber the OH was produced by natural light photochemistry. A general feature is that SOA produced from ozonolysis of α-pinene and limonene initially was rather volatile and becomes less volatile with time in the ozonolysis part of the experiment. Inducing OH chemistry or adding a new portion of precursors made the SOA more volatile due to addition of new semi-volatile material to the aged aerosol. The effect of OH chemistry was less pronounced in high concentration and low temperature experiments when lower relative amounts of semi-volatile material were available in the gas phase. Conclusions drawn from the changes in volatility were confirmed by comparison with the measured and modelled chemical composition of the aerosol phase. Three quantified products from the α-pinene oxidation; pinonic acid, pinic acid and methylbutanetricarboxylic acid (MBTCA) were used to probe the processes influencing aerosol volatility. A major conclusion from the work is that the OH induced ageing can be attributed to gas phase oxidation of products produced in the primary SOA formation process and that there was no indication on significant bulk or surface reactions. The presented results, thus, strongly emphasise the importance of gas phase oxidation of semi- or intermediate-volatile organic compounds (SVOC and IVOC) for atmospheric aerosol ageing.

Salo, K., Hallquist, M., Jonsson, Å. M., Saathoff, H., Naumann, K.-H., Spindler, C., Tillmann, R., Fuchs, H., Bohn, B., Rubach, F., Mentel, Th. F., Müller, L., Reinnig, M., Hoffmann, T., and Donahue, N. M.: Volatility of secondary organic aerosol during OH radical induced ageing, Atmos. Chem. Phys., 11, 11055-11067, doi:10.5194/acp-11-11055-2011, 2011. Link to article>>


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