Edmonton's greenhouse gas emissions have gone down. The city is studying why.

Total greenhouse gas emissions in the City of Edmonton dropped by the equivalent of 2.5 million tonnes of carbon dioxide over two years, data shows — and work is being done to find out exactly why.

Total emissions hovered around the 18-million-tonne range from 2015 to 2018. In 2019, emissions dropped about 900,000 tonnes to 17.3 million tonnes. In 2020, emissions totalled 15.7 million tonnes, data shows.

"I am incredibly excited that we've finally peaked and are on the decline for emissions," said Chandra Tomaras, the city's director of environment and climate resilience, a section of the environment, climate change and energy department.

"It's very encouraging and has me really optimistic that these big, bold targets are achievable."

The city's 2021 emissions data should be released some time in early 2022, after calculations are complete, Tomaras said.

The city tracks how much greenhouse gases it emits each year through burning fossil fuels, decomposition of waste and landfill sites, industrial processes, chemical use, and livestock and land. It also tracks how much emissions are naturally absorbed from the air through vegetation, such as urban forests and the river valley.

In 2015, council approved the Community Energy Transition Strategy. By 2035, it aims to cut emissions by 35 per cent, energy consumption by 25 per cent and see 10 per cent of Edmonton's electricity locally generated, compared to 2005 levels.

By 2019, however, global research suggested those goals wouldn't be enough to limit global warming and prevent the worst impacts of climate change.

The city declared a climate emergency and moved to amend its strategy so its goals aligned to prevent an 1.5-degree temperature increase.

In April, the updated strategy was released. It's a phased plan to make Edmonton a carbon-neutral city by 2050, with emissions targets the city will aim to hit along the way.

The first target: emit the equivalent of 11.8 million tonnes of CO2 in 2025.

The emissions decrease correlates with the city's climate emergency declaration, but Tomaras said she's currently unable to definitively say there's a link between the two.

"We're trying to understand [how] actions we have taken are contributing to that," she said.

"We're talking about significant and transformational action needed. And we're really scaling up and starting that."