A manager at one of the Northwest Territories’ diamond mines says the company plans to update the climate models it uses to map what could happen at the site in the decades after it closes.

The Diavik mine is expected to cease production in 2026 and be completely closed by 2029. It is one of three diamond mines in the process of closing in the territory and is striving to distance itself from a long history of abandoned mines by successfully abandoning mining. land on the territory.

Rio Tinto, owner of the mine, submitted the first version of its final closure and reclamation plan to the Wek’èezhìi Land and Water Board (WLWB) in 2022. This plan contained data from climate models that projected 100 years into the future.

Earlier this year, WLWB told the company it necessary to update its climate change modeling in its final performance evaluation report. It also asked the mine to operate models beyond 100 years – or propose a time frame for doing so, in the next version of its closure plan.

The question that now needs to be answered is when the company will do these two things.

Sean Sinclair, head of Diavik’s closure, told CBC News last week he was discussing with partners and stakeholders “when and how it is appropriate and best to update” the models.

He said performance assessment reports are produced after the mine closes and post-closure monitoring begins. They will show the board whether Diavik meets a variety of criteria and closure goals.

It has not yet been decided how often these reports will be published, nor when a final report might be produced.

Sinclair said Diavik’s “final position” on how and when to update climate models would be included in the next version of its final closure and reclamation plan, expected in April.

What is a climate model?

A climate model is a computer simulation that represents how energy and matter interact in different parts of the ocean, atmosphere and land.

They are tested by taking them back in time and seeing how they compare to what actually happened – and they can be analyzed to predict conditions under different warming scenarios.

Sinclair said climate models have long been incorporated into Diavik’s closure plans. They were used to design a site that, once handed over to the land, can handle flooding, heavy rainfall and large amounts of snow that could occur in the decades to come.

Climate scenarios were also considered in the design of the mine’s northern rock pile and processed kimberlite containment facility, two sites that exploit the cold temperature of the continuous permafrost beneath the East island of Lac de Gras.

“It blows my mind”

A University of Toronto modeling expert is impressed that the WLWB is telling Rio Tinto it needs to look further into the future with its plan to close the Northwest Territories diamond mine.

“It amazes me, in a good way, that the regulator is asking these questions,” said Steve Easterbrook, a computer science professor and director of the university’s environmental school.

But, he added, running longer-term climate models will be a challenge – and the results may not be very reliable.

WSP, the company that prepared Diavik’s climate projections, said it gleaned information from 24 models on Climatedata.ca, an online portal supported in part by the federal government.

Easterbrook said it’s the right data to use — it’s what he uses, too — but the organization probably doesn’t run its models beyond 100 years. The problem, he says, is that the further into the future you go, the more unreliable predictions become as uncertainties build up over time.

“A lot of climate scientists I’ve talked to say they don’t like to run their models more than 100 years into the future simply because they know that after that there’s just too much guesswork.”

Industry standard

Running climate models for about 75 years – until 2100 – appears to be an industry standard.

The Mining Association of Canada has published guidelines for adaptation to climate change in 2021. He said longer-term models applied until 2100 should be used for closure and post-closure work.

The federal government also has a guide on assessing the resilience of projects to climate change. It states that the majority of climate change simulations extend to 2100 and that simulations beyond that are available, but they are not as numerous and have more uncertainty.

The federal government is also proposing models out to 2100 for cleaning up the abandoned Giant Mine in Yellowknife – although the Giant Mine Oversight Board has called that timeline “short-sighted.” earlier this year.

Kirsten Zickfeld, a distinguished professor of climate science at Simon Fraser University in British Columbia, has previously worked on long-term climate simulations. She also acknowledges that they become less and less reliable as they advance, but says that they are very important for understanding components of the climate system that take longer to respond to change, such as oceans, ice sheets glaciers and permafrost.

She said project planners – for example, a company closing a diamond mine – could address uncertainties in long-term projections by pairing them with risk assessments.

“So maybe there’s a 70% chance in a given scenario… that the permafrost will melt in this specific area and then, as a decision maker, you have to decide, ‘OK, what does that mean? ? »

If Diavik uses climate models to understand what might happen at the mine site in 100 years, Easterbrook said it would need to look for other data sources.

“It’s possible, but yes, they’re going to have to go further than just using publicly available data on standard data sites,” he said. “This will reduce the number of experts available to perform this type of analysis.”