§ Mr. Chris Smith
To ask the Secretary of State for the Environment what is his assessment of the net effects on global warming of anthropogenic aerosols and particulates; and what assessment he has made of the global warming effects of particulates from diesel vehicles and the net effect of emissions from diesel vehicles on greenhouse gas emissions.
§ Mr. Atkins
The impact of anthropogenic aerosol particles on the climate is highly uncertain. In its 1992 Report the Intergovernmental Panel on Climate Change concluded that the present-day effect of all particles was probably a net cooling, with the cooling effect of sulphate aerosol particles exceeding the warming effect of particles containing elemental carbon, of which one source is diesel engine exhaust. The panel is currently reviewing this subject, in preparation for a report on the radiative forcing of climate due to be published later this year.
The main greenhouse gas emitted by diesel vehicles is carbon dioxide, and in 1992 these accounted for 6 per cent. of total United Kingdom CO2 emissions.