Carbon Impacts Tracer puts estimated climate harms alongside emissions figures

The Carbon Impacts Tracer is being launched to turn a quantity of carbon dioxide emissions into estimates of climate harm, including heat exposure and lost food production. Reported on 28 September ahead of a listed online launch event on 29 September, the tool gives readers a way to examine what emissions from a proposed project could mean beyond a single tonnage figure. Its outputs are model-based estimates, not damage already observed.

Scientists associated with the Australian National University, the Australian Research Council Centre of Excellence for the Weather of the 21st Century and the Lethal Humidity Global Council developed the tracer, according to The Guardian. The project was funded by the Minderoo Foundation. The UNSW Australian Human Rights Institute, a project partner, says the tool builds on a 2025 study that quantified the climate impacts of an individual fossil fuel project.

From emissions to estimated effects

Users can enter emissions associated with a project, company or state, or another known quantity, and receive estimates across eight impact factors, The Guardian reports. Its examples include food production lost to climate change, labour hours lost because of excess heat, glacier loss and coral deaths. The available reporting does not establish that a user can predict the precise damage at a particular mine or identify which individuals would experience an effect.

The calculation starts with the Transient Climate Response to CO₂ Emissions, or TCRE: a relationship between cumulative carbon dioxide emissions and global warming. The Intergovernmental Panel on Climate Change gives a best estimate of 0.45°C of warming per 1,000 billion tonnes of CO₂, with a likely range of 0.27°C to 0.63°C. The Guardian says the tracer then connects the resulting warming estimate to effects quantified in published climate studies.

A coal mine example

The proposed continuation of the Hunter Valley Operations coal mines in New South Wales is the tool’s prominent example. The Guardian reports an emissions estimate of about 809 million tonnes of CO₂ equivalent if the proposal proceeds. Renew Economy separately reported that owners Glencore and Yancoal seek a 19-year extension involving about 429 million tonnes of coal. Those figures describe the proposed project and its associated emissions, not emissions or climate damage that have already occurred under an approved extension.

For the 809 million-tonne emissions input, The Guardian reports that the tracer estimates about 0.00036°C of additional global warming. It also reports estimates of almost 500,000 people exposed to unprecedented heat and an annual crop-production loss equivalent to the minimum dietary requirements of 276,129 people. These are projections associated with the emissions quantity; they are not a count of people already exposed or food already lost because of this mine.

The paper also reports the tracer’s estimate of nearly 15 million coral-colony deaths each time the Great Barrier Reef bleaches. That figure is a modelled attribution to the entered emissions, conditional on a bleaching event. It does not mean researchers counted coral deaths caused by Hunter Valley Operations. The example illustrates how the tracer expresses a project’s possible contribution to a much wider climate effect, rather than measuring damage at the mine site.

Renew Economy reported that about 98% of the proposal’s estimated emissions would be scope 3 emissions associated with transport and combustion by end users. That distinction is relevant to the example: most of the projected emissions arise beyond the mining operation itself. The tracer’s harm figures use an emissions estimate, so a different estimate of the coal ultimately produced or burned would change the calculated results.

Why the estimates may matter

Professor Sarah Perkins-Kirkpatrick of the Australian National University, part of the team launching the tracer, told The Guardian that the aim is to make the effects of emissions legible and hold large emitters accountable. Maria Nawaz, who leads the Australian Climate Accountability Project at UNSW’s Australian Human Rights Institute, told the paper that linking a government’s or company’s emissions to climate harms has been difficult in litigation. She said the tool could help quantify that connection; that is her assessment, not a legal finding.

Climate lawyer Elaine Johnson, whom The Guardian identified as independent of the project, said some governments and companies may resist links drawn between fossil fuel products and harms such as heatwave deaths. The Guardian said it approached Glencore for comment and received no response. Its report did not include a response from Yancoal. Neither the tool’s estimates nor those reactions establish how a court or planning authority will weigh the figures.

For the Hunter Valley proposal, the decision is still ahead. The NSW Independent Planning Commission’s case page listed the applications as pending when checked on 28 September and gave 30 September as the extended decision deadline. The commission records public hearings in July, later requests for information and additional material received in early September. Its applications concern continued operation of the HVO North and South mines, with extraction proposed through 2042 and 2045 respectively.

The tracer offers a way to put an emissions estimate in terms of possible human and ecological effects while showing uncertainty around its calculations. For Hunter Valley Operations, the immediate question is whether the continuation proposal will be approved. Until that decision and any subsequent operation, the tool’s figures remain conditional estimates tied to the proposal’s emissions assumptions and the published impact studies used to interpret them.