I have frequently cited research on secondary aerosol particles, and while the linked reference concludes that cloud formation associated with such secondary aerosol particles will slightly reduce climate sensitivity; another way of looking at this research is that if/when the source of such secondary aerosol particles is reduced/degraded (such as by deforestation and wildfires), then near future climate sensitivity values will actually be higher that what AR5 reported/assumes.
Jasper Kirkby, Jonathan Duplissy, Kamalika Sengupta, Carla Frege, Hamish Gordon, Christina Williamson, Martin Heinritzi, Mario Simon, Chao Yan, João Almeida, Jasmin Tröstl, Tuomo Nieminen, Ismael K. Ortega, Robert Wagner, Alexey Adamov, Antonio Amorim, Anne-Kathrin Bernhammer, Federico Bianchi, Martin Breitenlechner, Sophia Brilke, Xuemeng Chen, Jill Craven, Antonio Dias, Sebastian Ehrhart, Richard C. Flagan, Alessandro Franchin, Claudia Fuchs, Roberto Guida, Jani Hakala, Christopher R. Hoyle, Tuija Jokinen, Heikki Junninen, Juha Kangasluoma, Jaeseok Kim, Manuel Krapf, Andreas Kürten, Ari Laaksonen , Katrianne Lehtipalo, Vladimir Makhmutov, Serge Mathot, Ugo Molteni, Antti Onnela, Otso Peräkylä, Felix Piel, Tuukka Petäjä, Arnaud P. Praplan, Kirsty Pringle, Alexandru Rap, Nigel A. D. Richards, Ilona Riipinen, Matti P. Rissanen, Linda Rondo, Nina Sarnela, Siegfried Schobesberger, Catherine E. Scott, John H. Seinfeld, Mikko Sipilä , Gerhard Steiner, Yuri Stozhkov, Frank Stratmann, Antonio Tomé, Annele Virtanen, Alexander L. Vogel, Andrea C. Wagner, Paul E. Wagner, Ernest Weingartner, Daniela Wimmer, Paul M. Winkler, Penglin Ye, Xuan Zhang, Armin Hansel, Josef Dommen, Neil M. Donahue, Douglas R. Worsnop, Urs Baltensperger, Markku Kulmala, Kenneth S. Carslaw, & Joachim Curtius, et al. (26 May 2016), "Ion-induced nucleation of pure biogenic particles", Nature, Volume: 533, Pages: 521–526, doi:10.1038/nature17953
http://www.nature.com/nature/journal/v533/n7604/full/nature17953.htmlAbstract: "Atmospheric aerosols and their effect on clouds are thought to be important for anthropogenic radiative forcing of the climate, yet remain poorly understood. Globally, around half of cloud condensation nuclei originate from nucleation of atmospheric vapours. It is thought that sulfuric acid is essential to initiate most particle formation in the atmosphere, and that ions have a relatively minor role. Some laboratory studies, however, have reported organic particle formation without the intentional addition of sulfuric acid, although contamination could not be excluded. Here we present evidence for the formation of aerosol particles from highly oxidized biogenic vapours in the absence of sulfuric acid in a large chamber under atmospheric conditions. The highly oxygenated molecules (HOMs) are produced by ozonolysis of α-pinene. We find that ions from Galactic cosmic rays increase the nucleation rate by one to two orders of magnitude compared with neutral nucleation. Our experimental findings are supported by quantum chemical calculations of the cluster binding energies of representative HOMs. Ion-induced nucleation of pure organic particles constitutes a potentially widespread source of aerosol particles in terrestrial environments with low sulfuric acid pollution."
http://www.businessinsider.com/new-climate-change-study-about-clouds-2016-5Also see:
Extract: "So, what's the deal with aerosols? Turns out that there are two sources of the particles:
1. Direct aerosol particles: produced by dust, sea-salt spray, or the burning of biomass
2. Secondary aerosol particles: formed when gas is converted into a particle — these are the type the scientists of the new study are interested in
Unlike what happens with direct aerosol particles, gas to particle conversion occurs everywhere. As a result, more than half of all the cloud seeds in the atmosphere are secondary aerosol particles!
This is where it gets tricky. Up until now, scientists believed that sulfuric acid, which is mainly produced from fossil-fuel emissions — cars, factories, etc. — were necessary for the formation of secondary aerosols. But in this new study, a group of scientists shows that Earth can actually produce these particles without any help from humans.
Instead, it gets made from a mix of tree vapors and highly energetic particles that bombard our atmosphere from outer space called cosmic rays.
…
This is where it gets tricky. Up until now, scientists believed that sulfuric acid, which is mainly produced from fossil-fuel emissions — cars, factories, etc. — were necessary for the formation of secondary aerosols. But in this new study, a group of scientists shows that Earth can actually produce these particles without any help from humans.
Instead, it gets made from a mix of tree vapors and highly energetic particles that bombard our atmosphere from outer space called cosmic rays."