In this study, the researchers used information from satellite data and from field research to survey the amount of vegetation across Leicester - a city with a population of about 300,000 people...

The team estimated that 231,000 tonnes of carbon, equivalent to 3.16kg per square metre, was locked away in the city's vegetation - most of which was stored by trees.

http://www.bbc.co.uk/news/science-environment-14121360

Good to know us tree wardens are at the frontline of climate change combat.
(Should point out tree wardens in the UK are volunteers, a person with the same title in another country maybe professionals employed by government).