By Larry Kummer,

Editor of the Fabius Maximus website

Summary: Scientists and journalists bombard us with news about the coming climate catastrophe, described as certain unless we drastically change our economy. This has plunged many into despair. The hidden key to these forecasts is RCP8.5, the worst case scenario of the IPCC’s Fifth Assessment Report — often erroneously described as the “business as usual” scenario. Understanding this misuse of science reveals the weak basis of the most dire warnings (which set the mood at the Paris Conference), and helps explain why the US public assigns a low priority to fighting climate change despite the intense decades-long publicity campaign.

“We’re going to become extinct. Whatever we do now is too late.”

— Frank Fenner (Prof emeritus in microbiology at the Australian National U); Wikipedia describes his great accomplishments), an interview in The Australian, 10 June 2010.

In the IPCC’s Fifth Assessment Report four scenarios describe future emissions, concentrations, and land-use. They are Representative Concentration Pathways (RCPs), the inputs to climate models that generate the IPCC’s projections. Strong mitigation policies lead to a low forcing level of 2.6 W/m2 by 2100 (RCP2.6). Two medium stabilization scenarios lead to intermediate outcomes in RCP4.5 and RCP6.0.

RCP8.5 gets the most attention, with its bold and dark assumptions. It is a useful and important scenario, a warning of what might happen if the 21st century goes badly. RCP8.5 is a useful and important scenario, a warning of what might happen if the 21st century goes badly. It should spur us to act. Unfortunately from its creation RCP8.5 has often been misrepresented as the “business as usual” scenario — and so became the basis for hundreds or thousands of predictions about our certain doom from climate change.

The result of this (part of a decade-long campaign) is widespread despair among climate scientists and more broadly, among Leftists. This misuse of RCP8.5 is a triumph of propaganda, but polls show its ineffectiveness (with climate change ranking at or near the bottom of public policy concerns). Yet each month brings more of the same.

What future does RCP8.5 describe?

“In 2002, as I edited a book about global climate change, I concluded we had set events in motion that would cause our own extinction, probably by 2030. I mourned for months …”

— “Apocalypse or extinction?” by Guy McPherson (Prof Emeritus of Natural Resources and Ecology, U AZ), Oct 2009.

The papers describing the RCP’s clearly state their assumptions, unlike most of those that follow them. RCP8.5 describes a bleak scenario, a hot and dark world in 2100 (since it’s powered by coal, perhaps literally dark) — even before considering the effects of climate change. Below are the key points, with graphs from “The representative concentration pathways: an overview” by Detlef P. van Vuuren et al in Climatic Change, Nov 2011. See this post for a more detailed look.

Rapid population growth and slow economic growth in RCP8.5

RCP8.5 assumes a doubling of Earth’s population to 12 billion by 2100, which is the high end of the current UN forecast. The UN gives a purely probabilistic forecast, not considering if the numbers are realistic. For example, this assumes the population of Africa grows from one billion to 5 billion, giving it a density roughly equal to that of China today (which requires a highly ordered society to survive). Nigeria’s population would rise from today’s 160 million to almost one billion in 2100. Possible, but hardly “business as usual”.

While population skyrockets, GDP would drastically slow — producing a massive increase in world poverty (reversing the trend of the past several decades).

Slow tech growth in RCP8.5 takes us back to a 19thC world

RCP8.5 assumes a slowing of technological innovation, most clearly seen in energy use. By 2100 energy efficiency has improved only slightly (reversing the current decades-long trend), so that despite GDP being one-third lower than under RCP2.6, energy consumption is over twice as large. Worse, we will have gone back to a 19th C-like future where the world in 2100 is powered by coal. This is possible, but not a “business as usual” scenario.

How did RCP8.5 come to describe a “business as usual” future?

“With business as usual life on earth is largely doomed.”

— John Davies (geophysicist, senior research at the Cold Climate Housing Research Center), 22 February 2014.

This useful scenario was hijacked to serve the apocalyptic visions of activists. Did this happen from scientists’ deliberate misrepresentation (a noble lie?) or carelessness? Who can say? Here are some examples of climate scientists misrepresenting RCP8.5.

Similar misrepresentations are commonplace by journalists and activists, such as these…

“The awful truth about climate change no one wants to admit” by David Roberts (writer) at VOX, 15 May 2015. He describes RCP8.5 as “The red line is the status quo — a projection of where emissions will go if no new substantial policy is passed to restrain greenhouse gas emissions.”

“The scenario with the most warming is the ‘business-as-usual’ RCP8.5” — in an article at Climatica (“You & the experts exploring climate science”).

Tales of nightmares based on RCP8.5

“Let a hundred flowers bloom and a hundred apocalyptic visions contend.”

— What Mao might say if he were a climate activist.

RCP8.5 became the basis for scores of studies describing horrific futures that appear almost inevitable (since large global public policy changes seem unlikely). But they seldom mention RCP8.5’s extreme assumptions. The following articles are examples of this year’s crop: most are from the past 3 months — part of the campaign to build hysteria for the Paris conference.

These misrepresentations of climate science are examples of the poor conduct by scientists that has characterized the public policy campaign about climate change, and which I believe caused the campaign to fail. That doesn’t mean that climate change will not have awful consequences. Merely that we’ll be unprepared for them.

It’s not too late to restart the debate

Every day we begin anew. The public policy debate about climate change can restart if we can get climate scientists to test the models from the first three Assessment Reports. The results from the past quarter-century will give us valuable data about their reliability, and perhaps break the current deadlock.

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