The Greater Toronto Area (GTA) comprises over 6 million inhabitants a significant share of Canada's 36 million inhabitants. The local emissions are driven by energy use, transportation and industrial activities. The city of Toronto has signed up to climate plans and many actions have been taken reduce the Emissions of the GTA. Thanks to a visiting fellowship from NSERC I could start the urban network of Environment Canada's Greenhouse Gas Measurement Program. By now 5 sites have been installed and we have learned many things over the last years thanks to the observations of Greenhouse Gases (CO2, CH4, N2O) as well as the their isotopic composition.

Research highlights:

- The emissions of CH4 in the Greater Toronto Area are significantly lower then global and regional emission inventories predict: more here

- The estimated emissions of N2O in the GTA seem to be realistic, but there is a seasonal component we will have to investigate further: also here

-  Measuring carbon isotopes (14C) did allow us to quantify the contribution of fossil fuel burning to the local increase in CO2. How? For Toronto and the GTA we found that ca. 80-90% of the local CO2 enhancement comes from fossil fuel burning. However, things are not as easy as we thought as significant amounts of 14C are released from Canadian nuclear power plants. Why? This is surely not a health issue as we measure tiny amounts of 14C with high precision, but for our community quantifying fossil fuel CO2 emissions precisely is crucial and we need to correct for those biases due to the anthropogenic 14C emissions. 

- Another carbon isotope (13C) helped to investigate which type of fuel (natural gas, gasoline, coal) are used in the GTA. Looking at the gradients in CO2 and 13C (see graph above) we found a strong seasonal cycle of domestic heating and daily changes... not surprising in a country with this climate, but it is exciting to validate this "feeling" by solid science: more here and here. The paper journal on the latest results is waiting to be submitted in 2015...

- Another real research highlight was to see the diligence, skill and passion of the Environment Canada colleagues. From technician to director everyone was committed to make the best measurements possible - that can then be provided to fellow scientists, decision makers and the general public.