Greenhouse gas (GHG) emissions in Ontario

When tracking began in 1990, Ontario emitted about 179 megatonnes (Mt) of carbon dioxide and other greenhouse gases (GHGs). Emissions rose through the 1990s and peaked at 208 Mt in 2000. Since then, eliminating coal-fired power, the recession, and more fuel-efficient vehicles have contributed to reductions in GHGs. In 2016, Ontario’s emissions were 161 Mt.

As of 2016, three-quarters of Ontario’s climate-changing GHG emissions were produced by burning fossil fuels. In other words, most of Ontario’s GHG emissions come from people driving cars and trucks, and heating buildings where we live and work. Transportation (35%) and buildings (21%) together represent most of Ontario’s GHG emissions from energy use (see figure below).

Ontario's 2016 greenhouse gas emissions by IPCC and economic sectors

Ontario’s 2016 greenhouse gas emissions by Intergovernmental Panel on Climate Change and economic sectors (in megatonnes of carbon dioxide equivalent, Mt CO2 e). Source: Environment and Climate Change Canada, National Inventory Report 1990-2016.

GHG emissions in Ontario by sector in 2016

GHG emissions from the transportation sector in 2016 were 34% higher than 1990 levels. That increase was primarily due to emissions from driving freight vehicles (trucks and trains). However, on-road passenger vehicles make up the majority of GHG emissions.




About 30% of Ontario’s GHG emissions were from the industrial sector, of which only 60% are from energy use, mainly due to heavy industry (primarily in the chemical and fertilizer sector). Moreover, industry’s GHG emissions were 28% lower in 2016 than in 1990.

GHG emissions from buildings are growing faster than from every other source except transportation, mostly due to using natural gas for space heating. GHG emissions from Ontario homes and buildings increased by 23% in 2016 from 1990. Commercial and institutional building emissions have increased, while residential emissions have not.

Agriculture and Waste

Approximately 12% of Ontario’s GHG emissions come from the agriculture and waste sectors. Agricultural practices produce mostly methane and nitrous oxide, from animal digestion, manure, soil and fertilizer use. In the waste management sector, decomposition and incineration predominantly produce methane.


Electricity generation was historically a major source of Ontario’s GHG emissions. In 2016, only 3% comes from this sector. Since we stopped using coal to produce electricity, the ability to reduce GHG emissions from electricity production has been nearly exhausted (96% of our electricity generation comes from low-carbon sources).


Ontario needs to dramatically decrease its reliance on fossil fuels over time, along with the rest of the world, to avoid the worst impacts of climate change and improve public health. Ontario’s homes, offices, cars and trucks will need to be significantly less carbon-intensive than they are today to reduce GHG emissions. Knowing where Ontario’s GHG emissions come from is a start.

Read our reports Making Connections: Straight Talk About Electricity in Ontario and Climate Action in Ontario: What’s Next? to learn more about Ontario’s’ GHG emissions to date and going forward.

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