Despite efforts around the world to address its effects, climate change remains one of the most pressing challenges of our time. To help meet that challenge, global enterprises like Omnicom must do our part to reduce greenhouse gas (GHG) emissions and lessen our environmental impact. We are pleased to report Omnicom made further progress in 2013 towards reducing our consumption of energy and increasing our use of renewable energy. We reduced our use of purchased electricity by nearly 3 percent in 2013 while sourcing nearly 10 percent of our electricity from renewable resources. We also reported a drop in our overall carbon footprint for the second consecutive year. Since 2007, Omnicom has cut its total carbon footprint by more than 12 percent.
Measuring Our Footprint
Omnicom performed its first large-scale carbon dioxide (CO2) emissions assessment in 2008. We engaged all of our 1,500 agencies to get a unified picture of electric, fuel, oil and natural gas consumption, as well as employee business-related automobile and air travel. This process brought us to what we're confident is an accurate CO2 emissions baseline.
Omnicom uses the guidelines established by The Greenhouse Gas Protocol Initiative (a partnership between the World Resources Institute and the World Business Council for Sustainable Development) to calculate our carbon footprint.
We gather data from about 1,000 separate locations to calculate our Scope 1, 2 and 3 level emissions. We then convert that data into our carbon emissions total (measured in metric tons) using formulas provided by GHG Protocols. We recognize the potential for human error with such a large number of individuals gathering and inputting data globally. To minimize misreporting, we validate against financial data, such as electricity and travel costs.
We collect our electricity consumption data in: a) kilowatt hours (kWh); b) cost in USD and c) office space in square meters. Our corporate Real Estate department is conducting an ongoing analysis on properties directly leased by Omnicom to determine energy efficiency on a property-by-property basis in those locations where Omnicom pays the direct electricity costs and has the ability to measure and monitor electricity usage. We use this data to rank properties by level of energy efficiency on two key data points: kWh cost per rentable square foot, and kWh cost per headcount.