In a world where people accept global heating is bad, news that we had avoided a boiling-in-our-own-juices version of the planet’s future might have been welcomed.
Instead, the news that a group of climate scientists had officially retired their very worst scenario for the future of the planet was proof – according to Donald Trump – that the scientists had been (in all caps) WRONG! WRONG! WRONG.
Picking up the baton this week, former editor of the Australian, Chris Mitchell, claimed the development “dramatically cuts the forecast warming of the planet by the end of this century”, in a dramatic mischaracterisation of what’s actually happened.
To understand why this is a gross mischaracterisation, we have to understand a bit of the background.
Since the 2010s, scientists have been using a range of scenarios in climate models to understand what might happen to the planet in the future. They were not forecasts, but rather a collection of “what ifs”.
Broadly, the scenarios relate to how many tonnes of greenhouse gases are let loose into the atmosphere from burning fossil fuels.
One of those scenarios was called RCP 8.5 – and its successor was SSP5 8.5. (The 8.5 refers to the amount of extra heat trapped in the atmosphere by the end of the century, measured – if you really want this detail – in watts per square metre).
This was the worst-case scenario, where the world’s population ballooned and fossil fuels continued to be discovered, drilled and burned to the point where global heating hits about 4.5C by the end of the century.
Other scenarios showed what might happen under lower levels of emissions.
For almost a decade, there has been a mostly polite debate among climate scientists about the appropriateness of using RCP 8.5 as it became clear that emissions won’t reach the level outlined in that scenario.
In May, the group of scientists responsible for advising the climate modellers wrote that the 8.5 scenario had “become implausible, based on trends in the costs of renewables, the emergence of climate policy and recent emission trends.”
The group suggested six new scenarios. Their worst-case imagined “a rollback of current mitigation policies” and global warming reaching about 3.5C by the end of the century – about 1C lower than under RCP 8.5.
Best case scenario also unlikely
Mitchell argued the 8.5 scenario had generated “hysteria” that had made people poorer, and that countries had committed to net zero by 2050 “on the basis of predictions the IPCC [Intergovernmental Panel on Climate Change] now accepts are way off kilter.”
There is a glaring problem with this claim (aside from attributing the change to the IPCC).
When countries went to Paris in 2015 to negotiate what level of global heating they wanted to avoid, they were not negotiating over the threat of temperatures rising by about 4.5C (but with an uncertainty range taking it over 5C).
They agreed that temperatures should be kept “well below 2C” and should aim for 1.5C.
Dr Andrew King, a climate scientist at the University of Melbourne, was among those behind the recommendation to use new scenarios.
“Climate scientists can’t predict the future so instead we construct scenarios of what could happen depending on what we do next,” he said.
“RCP8.5/SSP5-8.5 was always pretty much a worst-case scenario. Even though we haven’t done enough to tackle climate change over the last decade, we have seen enough decarbonisation that we won’t follow that path.
“It’s important to note that we also have dropped the most optimistic scenario for the 21st century with substantially higher peak warming in the new lowest emissions scenario than previously.”
So while we’ve avoided the worst future that climate scientists could imagine we have also acted so slowly that the best-case option is now implausible.
Shallow pool of contrarians
Standing not for the first time inside a glasshouse clutching a rock, Mitchell criticises climate scientists and journalists in some outlets – including this one – for failing to write a news story about the issue he spent more than 1,000 words misrepresenting.
Mitchell quotes the US-based Dr Roger Pielke Jr, who had written that the 8.5 scenario was “embedded in the policies and regulations of most of the world’s largest economies, found across the world’s most important multilateral institutions”.
But is that true?
Australia’s first National Climate Risk Assessment, released last year, did not use the scenario, instead warning of the myriad risks to the country under three different levels of global warming – 1.5C, 2C and 3C.
In recent years, regional climate modelling around Australia has also ignored the 8.5 scenario because there was growing agreement it was no longer relevant.
For example, the “high emissions” scenarios used in the most recent climate projections for Queensland, New South Wales and Victoria all used the lower emissions scenario (known as SSP3 7.0) for their worst-case projections.
Prof Glen Peters, an Australian climate scientist based at Norway’s centre for International Climate Research, has been one of the scientists calling for the 8.5 scenario to be scrapped.
He said: “I think the arguments of Mitchell and the like all falter, as they frame success as not [hitting] 4 to 5C warming in 2100. The policy world has prioritised ‘well below 2C’ and pursuing 1.5C. We are far from succeeding on that dimension.”
Mitchell describes Pielke Jr as a “former professor of environmental science at the University of Colorado”, but curiously doesn’t give his current role as a senior fellow at the American Enterprise Institute – one of a large group of conservative thinktanks that have fought for years to slow down progress on climate change.
The last time Pielke Jr was injected into the Australian climate debate – again by News Corp – he badly misinterpreted the national climate risk assessment to the detriment of all the people who read the front page of the Daily Telegraph upon which his misinterpretation was uncritically printed.
Mitchell also draws on comments from other contrarians, such as Danish political scientist Bjorn Lomborg, in his column.
You would not expect readers of The Australian to understand or remember that these commentators are drawn from the same shallow pool of contrarians that the newspaper continuously returns to.
But they are.
