Exclusive: Labor accuses Scott Morrison of using adjustments to Australia’s soil carbon data as an excuse not to act on climate change

Australia’s official greenhouse gas records have been adjusted such that emissions are now significantly higher than previously believed for the years when Labor was in power, and no longer rise each year since the Coalition repealed the carbon price.

The revisions, made clear in data published during the recent UN climate conference in Madrid, have allowed Scott Morrison to start claiming that emissions are now lower than when the Coalition was elected in 2013 and in any year when Labor was last in government.

That was not the case a year ago. As the graph below shows, changes to the data over the past year have increased emissions in the years of the Rudd and Gillard governments by between 3.5% and 6.7%. Emissions have been increased by smaller amounts or slightly reduced for the years since the Coalition regained power.

Most of the large revisions are due to a change in how the amount of carbon dioxide released from or absorbed by soil in grazing land is estimated.

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Guardian Australia asked several experts in greenhouse accounting about the changes. Some said they were legitimate and an improvement, as they factored in the impact of the climate crisis on soil carbon levels.

Others said the size of the changes, and the fact they significantly favoured the government’s narrative as it was facing rising criticism for not doing more to tackle emissions, warranted further explanation.

The total revisions in emissions from the land and forests, including soil carbon, across the years in the graph up to 2018 was 382.6m tonnes of carbon dioxide. For emissions from fossil fuel and other industries, 41.2m tonnes worth of adjustments were made.

Labor’s climate spokesman, Mark Butler, said he was concerned the government was using poorly explained revisions to emissions data to attack Labor and as an excuse not to act on climate change, singling out the emissions reduction minister, Angus Taylor.

“This minister has form,” Butler said. “I hope he’s not continuing that form by politicising the reporting of emissions data.”

A spokesman for Taylor said the emissions estimates by the Department of the Environment and Energy were made in accordance with international treaty requirements and subject to independent expert review each year.

The department said the latest inventory of data had been reviewed by the UN climate secretariat and a report was likely to be published next year.

Some experts told Guardian Australia the changes in soil carbon accounting made sense, but it was disingenuous for the government to take credit for it.

The increase in emissions from grazing land soil carbon under Labor was most likely a result of the millennium drought, which broke in 2010 but took another couple of years for the effects to be felt. Analysts said if the government took credit for soil carbon it would also have to take responsibility for the future increases in emissions from the land due to the current drought and bushfires.

Hugh Saddler, an energy consultant and ANU honorary associate professor at the Crawford School of Public Policy, said he respected the departmental officials who worked on greenhouse accounts and did not doubt the validity of their work.

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But he said calculating emissions from the land was a complex and arcane process, and that it would be better if national emissions accounts focused on areas over which people had greater control: electricity generation, transport, big industry, fugitive emissions from resource extraction, agriculture and the waste sector.

If emissions from what are known as land use, land-use change and forestry (LuluCF) are removed, Australia’s emissions have risen about 30% since 1990 and are nearly 20% higher than in 2000, contrary to the impression given when the government claims it is meeting its targets under UN accounting rules.

“These are the emissions we should be most focused on,” Saddler said.

Ursula Fuentes, a senior policy advisor with Climate Analytics, said emissions in most parts of the economy continued to increase. Pollution was falling only in electricity – due to the rise of cheap clean energy and the now-filled renewable energy target, which the government has chosen not to replace – and floods and drought affecting agricultural output. “There is a lack of policy across all sectors,” Fuentes said.

The significant changes that included the shift in how soil carbon emissions are modelled were first published in May. The large increase in the estimate of pollution for the years between 2008 and 2o13 smoothed what had previously been a noticeable rise in national emissions since the carbon price scheme was repealed in 2014.

In the most recent data, for the June quarter this year, industrial emissions were adjusted for years over the past decade. The department said it reflected new information from companies and revised energy consumption estimates back to 2014.

Following this change the data shows that, rather than rising annually under the Coalition, emissions have dropped slightly for the past two years. Combined, the two sets of changes have resulted in the emissions data now showing pollution was lower for each year under the Coalition than when Tony Abbott ousted Kevin Rudd in 2013.

The latest data was released just before Taylor flew to Madrid for a UN climate conference where Australia faced criticism for its plan to use an accounting measure to meet its 2030 target under the Paris agreement, a 26-28% cut below 2005 levels.

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The report including the data suggested, for the first time, that the government was expected to meet that target, but only if it counted carryover credits for beating previous targets under the expiring Kyoto protocol. Dozens of countries at the meeting opposed the use of the carryover credits amid claims they had no legal basis and were at odds with the commitment made in Paris to increase climate action over time.

Australia is the only country that has said it plans to use them. A decision on whether to ban them was pushed into next year.

Matt Drum, from climate change advisory business Ndevr Environmental, said discussion of carryover credits often ignored they were just a short-term book-keeping measure that would make it harder to reach net zero emissions by 2050, the ultimate goal of the Paris agreement.

“On the first of January 2030 our emissions will go straight back up because we have made no structural adjustment to our economy’s actual emissions,” he said.