New research initiated by teams at NUI Galway and the University of Helsinki has revealed that the true rate of global warming caused by greenhouse gases has been masked by the cooling effects of tiny airborne particles. According to the research these atmospheric aerosols — also known as particulate matter — form reflective haze and cloud layers which lead to an aerosol cooling effect. However new technologies and stricter environmental controls will see that effect reduced in the years ahead.
The new investigations show that the present-day aerosol cooling effect will be strongly reduced by 2030 as more stringent air pollution controls are implemented in Europe and worldwide, and as advanced environmental technologies come on stream. These actions are projected to increase the global temperature by 1°C and temperatures over Europe by up to 2 - 4°C, depending on the severity of the action. This is one of the main research outcomes of the recently concluded European Integrated project on Aerosol Cloud Climate and Air Quality Interaction (EUCAARI) project, which was funded by the European Commission.
The EUCAARI project, initiated by Professor Colin O’Dowd at NUI Galway’s Centre for Climate and Air Pollution Studies, who presided on the project’s management team, and led by Professor Markku Kulmala of the University of Helsinki, has provided new understanding of the impacts of aerosols and trace gases on clouds and climate.
“The quantification of the effect of aerosols on the radiative balance [cooling or heating] of the planet has been one of the most urgent tasks to underpin more informed projections of future climate change,” Professor O’Dowd explained. “Now that we have this data we need to reinforce European political decision-making to develop new strategies and implementation plans for global air quality monitoring and to take Europe into a leading role in developing and applying environmental technologies. Furthermore, it is urgent that higher-resolution EU-scale projections are conducted using a new generation of regional models nested within the global models.”
EUCAARI has been the most extensive atmospheric aerosol research project undertaken in Europe so far. The total budget of the project was €15 million, of which €10 million was provided by the European Commission Framework Programme 6. In all, 48 research institutes from 24 countries participated in the project between 2007 and 2010. The project has led to significantly more information on the physics of aerosol formation and its impact at all scales — from nanoscale to global, and from milliseconds to centuries.
The project performed extensive studies from ground-based, aircraft, and satellite platforms throughout Europe and in significant developing countries, namely China, South Africa, Brazil, and India. These studies have improved the theoretical understanding of the aerosol life-cycle, enabling scientists to make major improvements in climate and air pollution models and present new air pollution scenarios over Europe.
“The positive impacts of aerosols are partially offsetting global warming while the negative effects impact on public health,” Professor O’Dowd added. “Abatement of the negative health impact is complicated due to the diversity of sources, even within Europe.”
EUCAARI found that the reduction in ammonia emissions is one of the most effective ways to reduce aerosol mass concentrations in Europe. Reduction in nitric oxides is also effective, but might lead to higher ozone levels, causing another negative impact on air quality. Reduction in sulphur dioxide emissions will reduce particulate air pollution especially in the eastern Mediterranean region.
Reduction of organic aerosol concentrations is a lot more challenging and will require reductions of gas and aerosol emissions from transportation and biomass burning. It is now shown that a large fraction of organic aerosols in Europe is of modern origin (as opposed to fossil fuel origins), for which the main sources are biogenic secondary organic aerosol (organic chemicals released by plants and animals, much of which comes from the boreal forests across the northern hemisphere), biomass burning, and primary biogenic aerosol particles (bacteria and dead plant and animal cells).
“All these emission sources are expected to respond to climate change, although we are presently unable to gauge the strength of the multitude of feedback mechanisms involved,” Professor O’Dowd concluded. “The uncertainties in feedback highlight the need for improved Earth System Climate models to encapsulate feedback processes generally lacking in current projections.”