Carbon dioxide is one of the major GHGs and a driver in the domain of climate change. In the drive to mitigate and adapt with the issue of climate change, carbon trading has become a vital policy instrument in majority of the countries in the World. It is also a pivotal element of the UNFCCC’s (United Nation of Parties of Copenhagen Climate Change Conference) approach to tackle climate change. National or regional carbon trading schemes are now operational in many counties through a well-defined structural policy, specific for the country. Yet the trading is still in a volatile stage. Many schools think that this concept is not very realistic to combat climate change, while others consider this a strict regulation to put cap/limit on the emitters. Unfortunately, the subject is characterized by jargon, abstract concepts, mathematical formulae, and technical detail, making it hard for most people to understand its implications and evaluate its merits and demerits. This paper is a first order analysis to unravel some of this complexity by imparting thrust on three basic components – cap and trade, carbon offsets and carbon trading – which underpin the trade in carbon quotas. The case study of the highly urbanized city of Kolkata and Indian Sundarban mangrove ecosystem has been discussed in details with CO2 – e of dominant trees to analyze the probable credit that can be received from the producer communities of these two sites that are significantly different in terms of anthropogenic footprints and ecological features.