Summary: Let’s trace the misrepresentation and misuse of RCP8.5 from a new paper back to its earliest days. This shows how a big mistake and a small one combined to put much of climate science on a dead-end road. And how climate scientists’ refusal to recognize these mistakes has kept it on this road. Understanding the past can help climate science become more useful.

After three decades, the campaign for public policy action to fight climate change has failed to produce substantial results in the US. With vast investments of work and money, plus support of many powerful institutions, it ranks among the biggest such failures in US history. Let’s trace one reason for its failure, starting with a new paper and looking back through time to the original error. Remember, it is never too late to learn and change course.

William Nordhaus is a professor of economics at Yale and creator of the Dynamic Integrated Climate-Economy model (DICE), one of the most widely cited integrated assessment models providing guidance to policy makers about climate change. His latest paper goes to the heart of climate policy debate.

NBER working paper by William D. Nordhaus, May 2018.

The key message of the paper; red emphasis added.

“Concerns about the impact on large-scale earth systems have taken center stage in the scientific and economic analysis of climate change. The present study analyzes the economic impact of a potential disintegration of the Greenland Ice Sheet (GIS). The method is to combine a small geophysical model of the GIS with the DICE integrated assessment model. The result shows that the GIS is likely to disappear over the next millennium or so without climate policy, but an active climate policy may prevent the GIS from crossing the threshold of irreversibility. …” {Opening of the abstract.}

This is a well-constructed paper. It shares two typical characteristics of its genre. One is fun, the other has had awful effects.

Predictions over absurdly long horizons

“The ice-sheet decline is slow, with a GIS half-life of approximately eight centuries in the baseline path …” {ibid.}

What was high tech 800 years in the past? The wheelbarrow, rudder, and windmill were new inventions. The chimney would soon be invented. The hourglass and paper were a century away. Tech progress was slow. It accelerated in the 12th century, sped up again roughly 300 years ago, and reached incredible rates of progress in the late 19th century. Guessing what will possible even one century in the future is wild speculation.

Also, multi-century predictions of climate change should not be taken seriously. They are far beyond the state of the art.

Misrepresenting the future

“The arrow is the range of model estimates for a high warming scenario (RCP 8.5) from IPCC (2013) p. 1191, and has comparable forcings as the DICE-GIS baseline run.” {ibid.}

RCP8.5 is not just a “high warming scenario” but the worst-case scenario of the four used in AR5, aka IPCC 2013 (details here). As a worst-case scenario should, it assumes ugly changes in important long-term trends – such as tech (from progress to stagnation) and fertility (slow or stopping the decline in emerging nations). Each is unlikely; the combination is very unlikely.

Also, researchers have long questioned if the world has sufficient economically recoverable coal to fuel the 21st century – as RCP8.5 assumes. See two recent papers here (ungated copy here) and here.

If DICE-GIS has similar forcings, it must have similarly improbable assumptions. Therefore, it provides no basis for Nordhaus’ statement that “GIS is likely to disappear over the next millennium or so without climate policy.” He should have said that “under severe but unlikely circumstances, the GIS is likely to disappear over the next millennium.” But what’s the fun in that?

Climate scientists love to write about RCP8.5, from Bloomberg.

Unfortunately, many of these papers misrepresent RCP8.5. Activists trumpet these as predicting certain disaster unless we change our ways. This was the most recent act in the three decades-long campaign using doomster predictions to make the public support policy changes

Two things made this happen. The first was probably a small mistake. The second was a fateful decision by the climate science community.

A “business as usual scenario”

One of the earliest papers about RCP8.5 was “RCP 8.5 – A scenario of comparatively high greenhouse gas emissions” by Keywan Riahi (2011). They describe it as…

“The RCP8.5 combines assumptions about high population and relatively slow income growth with modest rates of technological change and energy intensity improvements, leading in the long term to high energy demand and GHG emissions in absence of climate change policies.”

In the text they gave an additional description.

“RCP8.5 depicts thus a relatively conservative business as usual case …”

This is, of course, correct. It is conservative from a risk management perspective – assuming the worst outcome. It is “business as usual” in the sense of assuming no change in climate-related public policy. It does not assume continuation of our world as it is; it assumes radical changes. The authors use these two terms in complementary fashion: trends change but public policy does not. An awful but unlikely scenario.

But many climate scientists interpreted these terms in the opposite way: that RCP8.5 assumes continuation of current trends (business as usual) but no change in policy. That makes the awful results of RCP8.5 quite terrifying. In a variant of Gresham’s Law, the papers misrepresenting RCP8.5 – with their vivid if exaggerated warnings – drove out the more sedate ones that correctly described it.

But climate scientists made a far larger mistake when designing the RCPs. They designed no RCP representing a “business as usual” scenario: the future if current trends (the exogenous variables, such as tech and population fertility) continue on their long-term path. That would provide the logical starting point for analysis by policy makers and the public, bracketed by more and less optimistic scenarios. This failure has distorted the climate policy debate since 2011, and does so to this day.

The worst mistake

“Insanity is repeating the same mistakes and expecting different results.”

— From Narcotics Anonymous (1981).

Mistakes and oversights become visible in hindsight. That is life, especially on the intellectual frontiers. History is shaped by how people respond after they become visible. During the past four years, many people pointed out the misrepresentations of RCP8.5 and the lack of a realistic “business as usual” scenario. They were ignored by the climate science community. Instead they have churned out scores, perhaps hundreds, of papers describing the terrifying future of RCP8.5. Many misrepresent the scenario; few put it in its actual context (examples here).

This seemed to work. Journalists loved these exciting papers. Climate scientists describing the most cataclysmic future had career success and fame (even if just their 15 minutes) before the prediction of doom arrived).

Activists took these papers and exaggerated them. Climate scientists, so active in fighting “deniers” (rightly so for the real deniers), seldom spoke out against activists misusing their work. The line between the two groups blurred, as they formed a marriage of convenience.

But since the 1960s, the American public has been bombarded with predictions of doom by activists seeking policy actions. The Boomers grew up amidst these. We have lived to see most proven wrong. They have become entertainment, scary headlines that do not affect behavior.

The bottom line

“Not long after civilization fails — and certainly by mid-2026 — the planet will harbor no humans.”

— From a post by Guy McPherson (Prof Emeritus of Natural Resources and Ecology, U AZ), February 2017. He is the author of Extinction Dialogs: How to Live with Death in Mind (2014). He predicted in 2017 that our species will be extinct by 2026.

What impact has three decades of doomster predictions about climate change had on the US public? In March 2018 the Yale Program on Climate Change Communication asked registered voters about their beliefs concerning climate change. See the full report, and especially the section asking about global warming and their intentions for the 2018 election. Only 38% of registered voters (38%) said it will be very important to their vote. Among liberal Democrats, 69% said global warming will be a very important issue.

Even more important is how voters ranked the many issues. Registered voters ranged global warming as 15th in importance among the 28 issues listed. It was only the ninth most important for all Democrats. Even for liberal Democrats it was only the fourth most important issue – probably “below the fold” (i.e., not affecting their vote).

The Future

Success requires learning from past mistakes. Failure is the usual result of political movements because people are seldom willing to do so. As Max Planck, the great physicist said…

“A new scientific truth does not triumph by convincing its opponents and making them see the light, but rather because its opponents eventually die, and a new generation grows up that is familiar with it.”

Other posts in this series

For More Information

For more useful information than Nordhaus’ speculation, see “The effect of a Holocene climatic optimum on the evolution of the Greenland ice sheet during the last 10 kyr” by Lisbeth Nielsen et al. in the Journal of Glaciology, in press. You might be surprised at the news. Hat tip to Anthony Watts.

Ideas! For shopping ideas see my recommended books and films at Amazon.

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