janroe

With the Copenhagen climate conference starting today, it's useful to calculate the carbon emissions for production and shipping of specific products. As a next step, an offset could be provided.

Some initial research on basic carbon calculations for shipping:

Definitions

Anthropogenic = manmade, Defra = UK Department for Environment, Food and Rural Affairs, GHG = Greenhouse gas, GWP = Global warming potential, UN IPCC = UN Intergovernmental Panel on Climate Change

CO2e stands for Equivalent Carbon Dioxide. It defines the effects of all gases that have global warming potential under one term, or "currency". That currency is CO2e. It is defined as the flow into (not a given concentration in) the atmosphere. Some gases have more or less impact, these can all measured in their equivalent CO2 values.
Source: http://en.wikipedia.org/wiki/Carbon_dioxide_equivalent
Some sources use CO2e as a concentration of parts per million (i.e 350 ppm CO2e). According to the definition above, this might indicate incorrect usage.

Conversion

GHC Conversion factors - converting other gases to CO2e:
Source: http://www.defra.gov.uk/environment/business/reporting/pdf/ghg-cf-guidel...

Price

The price of 1 tonne CO2e is said to be between 10-30 euro. It currently [7 Dec 2009] stands at 14.86 euro. That makes it 0.01486 euro per kg (or about 1.5 eurocent/kg). A lower price is shown at the second source.
Sources: http://www.pointcarbon.com/trading/ 14.86 +0.58 euro on 7 Dec 2009, http://www.co2e.com/

Air Freight

Figures for short, medium and long-haul are different. Also different calculators come to different conclusions.

Sea, rail, road-air freight
Air freight is calculated at 0.00189317 kg CO2e /km (avg 1.500 km assumed).
Source: http://www.carbonneutral.com.au/calc/cncalcip.pdf (on p22+ and re air travel on p10+):

Sending a small 3 kg air freight package from SEA to EUR (20.000 km) would then be 0.00189317 kg CO2e /km x 20.000 km = 113.59 kg CO2e. This 113.59 kg CO2e x 0.01486 euro/kg CO2e = 1.69 euro.

Interesting

Exploring the market for voluntary carbon offsets
Source: http://www.iied.org/pubs/pdfs/15502IIED.pdf

Up to four tons of carbon a year would be captured by each hectare?
Source: http://www.urbansprout.co.za/spekboom_soaks_up_co2

Summary Result

The CO2e offset cost for 3 kg air freight shipping from Southeast Asia to Europe is 1.69 euro.