David Staples: Climate scientists have already gotten it wrong with extreme forecasts. How and why?

By David Staples

We’ve all seen the dark and alarming headlines about the coming climate crises. It’s hard to know what to make of them.

If we’re not being told of attacks of extreme flooding or threats of Biblical rainfall, we’re hearing that climate change is already making droughts worse or that climate change will impact poor countries far more than rich ones.

But the most alarming headlines tend to be based on scientific papers using implausible scenarios of the future, scenarios that were never meant to inform real world climate policy, says Prof. Roger Pielke Jr. of the University of Colorado Boulder, who has studied climate change and policy for 25 years

“So much of climate science is based on implausible scenarios … they have no connection to the real world. They should play no role in climate research to inform plausible projections of climate impacts or policy.”

Misleading science threatens the credibility of the Intergovernmental Panel on Climate Change (IPCC), Pielke Jr. said., and the extreme policies based on such bad science won’t stand up to court challenges, let alone remain politically popular and lead to the incremental change needed to address climate change, which is indeed a real problem with largely negative consequences.

In his research, including a new peer-reviewed paper in a respected science policy journal, Pielke Jr. and co-researcher Justin Ritchie of the University of British Columbia have found that almost all IPCC climate science projections of future carbon emissions, first made in 2005, can now be seen to have over-estimated present day carbon emissions.

Worldwide CO2 emissions rose from about 28 gigatons (Gt) of CO2 per year in 2005 to about 33 GtC02 in 2020. But the IPCC climate scenario most likely to be referenced by climate scientists and journalists, known as the RCP8.5 model, predicted the world would be using about 42 GtCO2 by 2020.

The highly influential RCP8.5 predicts the world burning about 60 GtCO2 per year by 2040, even as that now seems highly unlikely.

“They’re not just implausible, they are to several decimal points just functionally impossible,” Pielke Jr. said of the most extreme scenarios. “These are futures that are interesting but are not going to happen.”

How did our climate scenarios get off track?

Pielke Jr., author of The Climate Fix, explained his thinking at length in an online speech and Q&A session hosted by Arizona State University this week.

Future scenarios

Scenarios of the future are fundamental to climate research and policy, he said. They help climate scientists understand potential impacts to societies, ecosystems and the climate. Scientists dig into plausible scenarios to assist with real world policy choices, but also engage in exploratory scenarios to study what might happen in various cases, including extreme and unlikely scenarios.

The IPCC’s first task in 1990 was to develop such scenarios, comparing a plausible “business as usual” approach to other plausible scenarios where less fossil fuels were used, Pielke Jr. said.

But by 2000 that changed. Exploratory scenarios were increasingly used as the IPCC’s basis for making climate and socio-economic forecasts. In this way, an extreme exploratory scenario, RCP8.5, with its temperature increase of as much as 5.4 degrees by 2100, became the go-to model as the “business as usual” comparison, even though it was never designed to be that.

I asked Pielke Jr. if he saw politics at play here. Maybe activist scientists were seeking to alarm people and thus push preferred policies?

He discounted this notion, pointing to other similar massive research mistakes which have been made in an apolitical field like cancer research.

But he did note that extreme scenarios make for alarming findings, which can generate wanted attention for scientists and splashy headlines for writers.

Science for those who are not experts

What are we to make of Pielke Jr.’s findings, those of us who want to do the right thing here but are not scientific experts?

First, I suggest we take Pielke Jr.’s ideas as that of an expert but realize he’s one of many experts in a wide and contentious field.

Second, that Pielke Jr. has good advice on the importance of getting it right with science to make informed policy decisions: “We should have a very low threshold when science goes off track,” he said. “And it’s OK to critique scientists. It’s what we expect and it’s what makes science better. Don’t let people say, ‘You’re not allowed,’ and ‘You can’t critique consensus science.’”

Third, and most crucially, any time we see a news story, a scientific study or a government policy on climate change, it’s worth digging into which IPCC scenario it’s based upon to assess its credibility. If it’s based on RCP8.5, that’s a red flag.

This article appeared on the Edmonton Journal website at


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