Reposted with permission from Forbes

Roger Pielke

Energy

In recent years the issue of climate change has taken a decidedly apocalyptic turn. Earlier this week United Nations Secretary-General António Guterres warned, “If we don’t urgently change our way of life, we jeopardize life itself.” A group of scientists writes that we “might already have lost control” over “tipping points” in the Earth’s climate, warning that the “stability and resilience of our planet is in peril.”

It’s true that apocalyptic narratives have always had a place in discussions of climate. In 1989 the United Nations warned that the world had “a 10-year window of opportunity to solve the greenhouse effect before it goes beyond human control.” But the escalation of apocalyptic climate rhetoric in recent years is unprecedented. The drumbeat of doom has led some prominent figures to turn on the mainstream climate community, complaining that “climate scientists have been underestimating the rate of climate change and the severity of its effects.” In reality, climate science has not just accurately anticipated unfolding climate change, but has done so consistently for the past 50 years.

There is thus an inconsistency here. Discussions of climate change have become more apocalyptic, but climate science has not. I have been working hard to understand this inconsistency, and while I don’t yet have all the answers, I have identified a big part of the puzzle, which I can report here for the first time.

Discussions of climate change are directly and indirectly shaped by the work of experts who work under the umbrella of the U.N. Intergovernmental Panel on Climate Change or IPCC. The IPCC was established in the 1980s to assess and summarize climate science to inform policy makers, and since then has produced five major assessment reports, along with periodic topical assessments.

I have testified before the U.S. Congress on multiple occasions on the critical importance of the IPCC. The IPCC plays such an important role that if it didn’t exist, we’d have to invent it. Research on climate change results in a large and varied literature that would be impossible to comprehend without expert assessments like those of the IPCC. The IPCC thus serves a crucial role at the intersection of science and policy.

Human-caused climate change is of course real and a significant concern. I have argued for decades about the importance of policies to mitigate carbon dioxide emissions and the need to better adapt to climate variability and change. But effective policy making is presently threatened by the apocalyptic turn in the climate debate.

Decisions made within the IPCC have contributed to the apocalyptic turn in discussions of climate, moving us away from constructive discussions, scaring children and contributing to overheated rhetoric. To understand the role of the IPCC in in recent rise of climate doom requires understanding how the body performs its assessments.

Underpinning everything that the IPCC does in its scientific assessments are scenarios of the future. Such scenarios are used to project future climate change, to project the impacts of such change on society and the environment, and to project the costs and benefits of mitigation action intended to reduce those impacts.

In order to produce such projections, in its scenarios the IPCC has long differentiated between “baseline scenarios” of the future which describe where the world is headed in the absence of climate policies and “mitigation scenarios” which describe a world where climate policies are put into place. Baseline scenarios are often referred to as “business as usual.”

The rise of the new climate apocalysm can be traced directly to an consequential but little appreciated change in how the IPCC presents its scenarios. The consequences of this change have reverberated through the scientific community, media reporting, policy discussions and civic advocacy.

Almost two decades ago the IPCC developed a set of scenarios as the basis for integrating the work of its three working groups on science, impacts and mitigation. The scenarios were created to serve as the basis for projecting future climate change, the impacts of climate change and the consequences of mitigation action. Such coordination across the assessment work of the IPCC makes obvious sense.

At the time the IPCC recognized that “the future is inherently unpredictable and so views will differ as to which of the storylines and representative scenarios could be more or less likely. Therefore, the development of a single “best guess” or “business-as-usual” scenario is neither desirable nor possible.” Based on this perspective, the IPCC developed a set of scenarios for our collective futures but did not identify any of them as more probable than another, explaining that, “the term “business-as-usual” may be misleading” and “most climate scenarios considered in this report can be regarded as exploratory.”

The result of this approach was that projected futures in the absence of climate policies encompassed a very wide range of possible outcomes. The fourth assessment report of the IPCC published in 2007 acknowledged this wide range of futures, “There is still a large span of [carbon dioxide] emissions across baseline scenarios in the literature, with emissions in 2100 ranging from 10 GtCO2 [billion tons of carbon dioxide] to around 250 GtCO2.”

In other words, when it came to carbon dioxide emissions from the burning of fossil fuels and the associated climate consequences, the long-term future included possibilities that spanned from the highly optimistic (the 10 billion ton scenario) to the highly pessimistic (the 250 billion ton scenario), and everything in between. Climate change was not necessarily apocalyptic, but possibly could be if we made decisions leading to bad outcomes.

An enormously consequential change in approach occurred from the forth IPCC assessment report in 2007 to the its fifth in 2013. The IPCC abandoned its earlier acknowledgement of fundamental uncertainties and ignorance about the future and instead fully endorsed the notion of choosing a “business as usual” scenario for the future. The “business as usual” scenario adopted by the fifth IPCC assessment was associated with one of its most extreme scenarios of the future.

The fifth IPCC assessment report states that while future greenhouse gas emissions were uncertain, “between 1970 and 2010, emissions increased 79%, from 27 Gt of [greenhouse gases] to over 49 Gt [billion tons]. Business-as-usual would result in that rate continuing.” An increase of that rate to 2100 would result in 189 billion tons of greenhouse gases being emitted at the end of the century, which is in the 99th percentile of all scenarios included in the database of reference scenarios of the fifth assessment report.

The fifth assessment report went further and explicitly identified a subset of reference scenarios that characterized where the IPCC believe the world was heading in the absence of climate policies. The IPCC fifth assessment report’s range of 2100 carbon dioxide emissions for “business as usual” is 50 GtCO2 to 106 GtCO2 (which it describes as the 10% to 90% percentiles of its scenario database). The report went further and identified a single scenario as “business as usual” with 2100 carbon dioxide emissions of more than 80 billion tons of carbon dioxide (this scenario is called RCP 8.5).

From the IPCC’s fourth to fifth assessment report our collective future, as envisioned by the IPCC, changed dramatically. The world was no longer heading for a wide range of possible futures, conditioned on enormous uncertainties, but instead was heading with some certainty toward a future characterized by an extreme level of carbon dioxide emissions. Quantitatively, futures with less than 50 billion tons of carbon dioxide emissions in 2100 simply disappeared from the IPCC scenarios and the focus was placed on a “business as usual” scenario of more than 80 billion tons of carbon dioxide emissions in 2100.

The apocalypse had been scheduled.

The decision by the IPCC to center its fifth assessment report on its most extreme scenario has been incredibly consequential. Thousands of academic studies of the future impacts of climate change followed the lead of the IPCC, and have emphasized the most extreme scenario as “business as usual” which is often interpreted and promoted as where the world is heading. For instance, so far in 2019 two new academic studies have been published every day that present this most extreme scenario as “business as usual” and predict extreme future impacts. Journalist promote these sensationalist findings, which are amplified by activists and politicians and as a consequence climate change becomes viewed as being more and more apocalyptic.

The problem with the extreme “business as usual” scenario of the IPCC’s fifth assessment report is that it is already out of date. For 2020 the scenario wildly overstates emissions, and has been critiqued in the academic literature as a highly unlikely if not impossible future. The International Energy Agency has proposed scenarios for the next several decades that diverge greatly from the favored scenario of the IPCC. It is of course possible that the world will collectively choose to emit massive quantities of carbon dioxide, which would require a massive increase in coal burning. But that scenario is certainly not preordained, and other futures are certainly possible.

Remarkably, the IPCC is set to repeat its reliance on extreme scenarios as “business as usual” in its forthcoming sixth assessment report, even though these scenarios are already out of date.

I will have much more to say on this subject in coming columns, as this topic is an active focus of my research. The bottom line for today is to understand that a fateful decision by the IPCC to selectively anoint an extreme scenario from among a huge range of possible futures has helped to create the climate apocalypse, a scary but imaginary future.

Follow me on Twitter @RogerPielkeJr

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