How many kilograms of carbon dioxide do you generate by browsing the web?

It’s the sort of question that’s becoming increasingly important as we move towards a zero carbon economy. But how do you measure it?

A new Google Chrome plugin developed by Scotch whisky maker Johnny Walker together with environmental consultancy Carbon Analytics claims to be able to calculate just that. By measuring online usage over four weeks, the Earth Mode plug-in calculates the user's annual consumption of energy.

Users will be able to see their carbon usage displayed as the equivalent of everyday activities such as using a microwave, driving a car or taking a flight.

The plugin has been timed to coincide with this Friday's Earth Day, the yearly event now in its 46th year. More than one billion people in 192 countries participate in Earth Day activities every year. 

According to Carbon Analytics' research, the average internet user consumes 130kg of carbon a year. That means each person needs to plant four trees every year to offset their carbon emissions. 

To offset the plugin, Johnny Walker will plant up to 75,000 trees as part of the Earth Day Network’s Canopy Project. The project has planted more than three million trees since 2011, many in East Africa. Earth Day Network is a global movement that aims to inspire, challenge ideas, ignite passion, and motivate people to take action on environmental issues.

The plug-in would help make people more aware of their own personal carbon emissions, said Earth Day Network president Kathleen Rogers.

"The more readily-available the information on our carbon footprint becomes, the more in contact with it in real-time we are, the more of an impact it will have. No more out-of-sight-out-of-mind. Now, like tracking the battery life on our cell phones, we will know what our computer usage is costing. And it will be eye-opening."

The Earth Mode plug-in can be downloaded from the Google Chrome app store.