The carbon dioxide emissions from additional passengers travelling by air under options one, two, and three in the “Adding Capacity at Heathrow Airport” consultation are set out in annex B of the consultation document, available at:
http://www.dft.gov.uk/consultations/open/heathrowconsultation/consultationdocument/
Carbon dioxide emissions from additional surface access trips to Heathrow would depend on the detail of the surface access strategy accompanying any extra capacity. This would need to be developed by the airport operator as part of a comprehensive transport assessment prior to a planning application.