Is there a bias in our land carbon reporting?

How is Australia tracking towards its commitment to cut carbon emissions by 43 per cent by 2030, and to reach net zero by 2050, and how much faith can ordinary citizens have in the answers they get? These are the questions for our age.

Since it began quarterly greenhouse reporting to the UN in 1991, Australia has been refining its methods of measuring emissions, using national inventory data and other sources covering manufacturing, energy use, transport, population, agriculture and weather.

Serving as a check against this “bottom up” approach are CSIRO “top-down” measurements of greenhouse gas concentrations at Cape Grim and Darwin, complemented by ancient air samples extracted from Antarctic ice.

Our reports are said to be well-regarded by the UN, but there remains a high level of uncertainty in one critical category, land use, taking in the huge quantity of carbon flowing in and out of soils and trees. It’s important to keep this under review because trees taking up carbon are the basis of most offsetting schemes – without which the world’s 2050 net-zero targets, including ours, would be unachievable.

Ketan Joshi, an Australian data analyst and writer now living in Norway, took a forensic look at Australia’s land-use emissions data in a post in Giles Parkinson’s Renew Economy last week. His focus was the parameters we use to determine which information is admissible and which isn’t, and how those parameters have been adjusted over the years.

Joshi began with an analogy from NSW public transport: “I remember the time that NSW solved the problems of late trains by changing the definition of late. It didn’t make our lives as commuters any easier, but hey: it did result in fewer late trains. Our problem was not solved. Their problem was.”

A similar mindset, where perceived success is more important than actual success, said Joshi, appears to be influencing the way Australia accounts for its land carbon. He got to work on the emissions data over the decade to last December, and came to the conclusion some sort of political influence was being brought to bear on the way successive Australian governments account for land carbon. 

There’s genuine scientific value in coming to grips with how land carbon works, and Australia is a prominent contributor to this work in gathering historical data and using models to refine that record in periodic revisions. But a trend in the effect of those revisions, previously noted in 2019 by policy analyst Michael Mazengarb and climate scientist Bill Hare, is starting to look disturbing. 

A fortnight ago, Hare observed that “every time the government recalculates how much carbon the land use sector is storing, the less work it has to do on actually cutting emissions from fossil fuels and industry sectors… 24 per cent by 2030, rather than 32 per cent. These changes to land use accounting may sound arcane, but they have very real consequences.”

Joshi commented: “You can see how this is a sort of pincer movement of adjustments: base year goes up to weaken the target, and recent years go down, to further narrow the gap of reductions required.” Adjusting 2005 emissions allowed scope for millions more tonnes of emissions to be released in the year 2030: “roughly equivalent to keeping one of the country’s biggest coal plants open. How lovely.”

“And how gloriously auspicious that every revision to Australia’s emissions accounting method results in the numbers tilting specifically up in the base year, and tilting specifically down in recent years.”

Just hours after Hare’s article was posted the Australian government published its latest emissions report, revealing, as Joshi described it, land use emissions dropping by about six million tonnes per quarter for the past three years – “the most significant downwards revision of recent history of emissions data ever.”

The 2005 baseline adjustments were the subject of some lively email discussion among members of Climate Tasmania last week. Scientists in the group advised that the revisions were part of the normal process of refining models and warned against inferring that there had been political conspiracy. 

We need to have enough faith in scientific processes and safeguards to discard any notion that the Albanese government or any of its predecessors have cooked the books. There is no conceivable avenue for direct political interference in that process – certainly not in Australia.

But governments face immense pressure to show policies succeeding and emissions declining (a pressure increased further by the Coalition’s new policy to defy the Paris Agreement and dump Labor’s 2030 target). In these circumstances bias – conscious or unconscious – is unavoidable.

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