Climate change is greatly impacting Canada's environment and landscapes. Extreme weather has become more frequent and severe because of the continued release of greenhouse gases into the atmosphere. The number of climate change–related events, such as the 2021 British Columbia Floods and an increasing number of forest fires, has become an increasing concern over time. Canada's annual average temperature over land warmed by 1.7 °C (3.1 °F) between 1948 and 2016. The rate of warming is highest in Canada's north, the Prairies, and northern British Columbia. The country's precipitation has increased in recent years and wildfires expanded from seasonal events to year-round threats.

As of 2022^[update], Canada was the world's 11th highest emitter of carbon dioxide (CO₂) and as of 2021 the 7th highest emitter of greenhouse gases. Canada has a long history of producing industrial emissions going back to the late 19th century. In 2022 transport, oil and gas extraction, and fugitive emissions together emitted 82% of the country's total emissions. From 1990 to 2022, GHG emissions from conventional oil production increased by 24%, those from multi-stage fracturing techniques increased by 56%, and emissions from oil sands production increased by 467%. This has led to criticism against Canada for committing to reducing greenhouse emissions while supporting its oil and gas industry.

Canada committed to reducing its greenhouse gas (GHG) emissions by 30% below 2005 levels by 2030 under the Paris Agreement. In July 2021, Canada enhanced the Paris Agreement plans with a new goal of reducing emissions by 40–45% below 2005 levels by 2030, enacting the Canadian Net-Zero Emissions Accountability Act. In 2019, the House of Commons voted to declare a national climate emergency in Canada. Several climate change mitigation policies have been implemented in the country, such as carbon pricing, emissions trading and climate change funding programs.

Climate change is the result of greenhouse gas emissions, which are produced by human activity. Canada was the world's 7th largest greenhouse gas emitter in terms of GHG Inventory data, as of 2021. In 2020, Canada emitted a total of 678 million tons of carbon dioxide equivalent (Mt CO₂eq) into the atmosphere. This represents a decrease from 1.8% of global emissions (730 Mt CO₂eq) in 2005 to 1.5% in 2020, but still an increase from 602 Mt CO₂eq in 1990. In 2022, Canada’s GHG emissions were 708  Mteq, still below pre-pandemic (2019) emissions, but an increase of 9.3 Mt (1.3%) compared to 2021. The Canadian Climate Institute reported a net drop of about 1% in emissions during 2023, largely due to the electricity and housing sectors. In contrast, emissions from oil, gas and transportation continued to rise.

The WRI's Climate Analysis Indicators Tool estimates that, between 1950 and 2000, Canada had the highest greenhouse gas emissions per capita of any first world countries. In 2020, of all the G20 countries, Canada was second only to Saudi Arabia for greenhouse gas emissions per capita.

Canada has one of the heaviest climate debts in the world, with a very long history of producing industrial greenhouse gas emissions. As of 2021^[update] Canada is the 10th heaviest cumulative emitter as assessed by model-based land-use mitigation measures, with 2.6% of cumulative emissions. Canada's 65.5 billion tonnes of carbon come roughly equally from use of fossil fuels and from deforestation and land use.

Electricity consumption in Canada in 2017 accounted for 74 carbon dioxide equivalent Mt CO₂eq, or 10% of the country's emissions. This sector's climate footprint significantly reduced in recent decades due to the closure of many coal-fired power stations. As of 2017, 81% of Canada's electricity is produced by non-emitting energy sources, such as hydro, nuclear, solar or wind power.

Fossil fuels provide 19% of Canadian electric power, about half as coal (9% of the total) and the remainder a mix of natural gas and oil. Only five provinces use coal for electricity generation. Alberta, Saskatchewan, and Nova Scotia rely on coal for nearly half their generation while other provinces and territories use little or none. Alberta and Saskatchewan also use a substantial amount of natural gas. Remote communities including all of Nunavut and much of the Northwest Territories produce most of their electricity from diesel generators, at high economic and environmental cost. The federal government has set up initiatives to reduce dependence on diesel-fired electricity.