I have not done the calculation yet but would assume from all the hype that our trip on our bikes will leave a smaller foot print than flying home. So lets see how the standard direct flight from London to Cape Town compares with our proposed trip via the Middle east and east Africa : http://www.climatecare.org/guardian/calculators
Both of us taking the same flight one way from London Heathrow to Cape Town Airport:
Your emissions from this flight are: 2.82 Tonnes of CO2. The cost to offset this CO2 will be £21.18
I couldn't find a calculator for a motorbike but I know our bikes do 22lt/500km petrol so that is 4.4lt/100km. Assuming higher use in sand and 2x bikes, so apply 10lt/100km to a car for 20,000km:
Your emissions from this car are: 4.6 Tonnes of CO2. The cost to offset this CO2 will be £34.50
Ooops....well who believes in Global warming anyway...
But seriously, that is a surprising result which contradicts all the hype about flying being bad. Just goes to show that you can't believe eveything on TV.