With the Sixth Assessment Report of the United Nations Intergovernmental Panel on Climate Change (IPCC) being released, it’s important to revisit the climate scenarios that are its centerpiece. These scenarios form the basis of the climate science community’s modeling and projections, which in turn affects governance and investment decisions across the world. Trillions of dollars and the policymaking of the entire planet thus ride upon these climate scenarios, so the cost of getting things wrong is extremely high.
The previous generation of climate scenarios published in the Fifth Assessment Report in 2014 were known as Representative Concentration Pathways, or RCPs. The RCP scenarios were labeled according to the amount of radiative forcing expected by the end of the century in each case. Radiative forcing is the scientific term for the change in the balance between the Earth’s incoming and outgoing energy. The Fifth Assessment Report focused on four of these scenarios, with RCP2.6 having the least warming and thus being the best case.
In the eight years since then, a new generation of scenarios has been developed for the Sixth Assessment Report, referred to as Shared Socioeconomic Pathways, or SSPs. The five main SSP scenarios are also labeled according to radiative forcing, but in addition each has a subtitle that tells a story about an imagined future:
A scenario is only as plausible as the assumptions it makes. Unfortunately, the technology assumptions made in both the RCP and SSP scenarios are not remotely plausible, and as a result they are extremely misleading. If there were even one scenario that made genuinely plausible assumptions, then the others could be useful for comparison. But the lack of any properly plausible one means that, taken together, these scenarios will only cause harm by leading decision-makers and the public badly astray.
First and foremost, all RCP and SSP climate scenarios get technology wrong because they fail to understand the forces that drive technological change, how quickly the shift to new technologies occurs and how quickly old technologies are abandoned as a result.
Our team at RethinkX has shown that the same pattern of disruption has occurred hundreds of times over the last several thousand years. Again and again, for technologies of all kinds–from cars to carpenter’s nails, from arrowheads to automatic braking systems, from insulin to smartphones–we see that technology adoption follows an S-curve over the course of just 10-20 years. The first phase of the S-curve is characterized by accelerating (or exponential) growth, which is driven by reinforcing feedback loops that make the new technology increasingly more competitive while at the same time making the old technology increasingly less competitive.
Unfortunately, the RCP and SSP climate scenarios show no sign that their authors understand technology disruption at all. For example, the best case RCP2.6 scenario in the Fifth Assessment Report published in 2014 assumed that less than 5% of global primary energy would come from solar, wind and geothermal energy combined in the year 2100.
Source: Adapted from Van Vuuren et al., 2011, and IPCC, 2014.
In reality, the exponential trend in the growth of solar and wind power had already been clear for over two decades at the time the Fifth Assessment was published in 2014, and the trend since then has only continued–as shown in the chart below.
(Note that the vertical axis of the chart is logarithmic, increasing by a factor of 10 at each major interval, which means the trajectory is exponential.)
On their current trajectory, which has been extraordinarily consistent for over 30 years, solar and wind power will exceed the RCP2.6 assumption for the year 2100 before 2030, 70 years ahead of schedule on an 86-year forecasting timeframe.
This is an egregious error that was entirely avoidable. The energy sector has shown every sign of becoming a textbook example of disruption for more than 15 years, and technology theorists were noticing the signs well before 2014. Indeed, Tony Seba–co-founder of RethinkX–had already published an analysis of the energy disruption in his book Solar Trillions in 2010.
Since 2014, the exponential growth of solar power has become common knowledge, as have similar trajectories for batteries and electric vehicles. It is therefore completely inexcusable that the same mistakes have continued in the new SSP scenarios for the Sixth Assessment Report in 2022. The SSP5-8.5 scenario, for example, is titled “Fossil Fueled Development”. Here is its description:
“This world places increasing faith in competitive markets, innovation and participatory societies to produce rapid technological progress and development of human capital as the path to sustainable development. Global markets are increasingly integrated. There are also strong investments in health, education, and institutions to enhance human and social capital. At the same time, the push for economic and social development is coupled with the exploitation of abundant fossil fuel resources and the adoption of resource and energy intensive lifestyles around the world.”
This logic around “rapid technological progress” is not just wrong, it’s backwards. The faster we make technological progress, the less fossil fuels we will use. The more global markets are integrated and the more human and social capital we have, the faster we will decarbonize.
The SSP3-7.0 scenario contains the same error:
“Technology development is high in the high-tech economy and sectors. The globally connected energy sector diversifies, with investments in both carbon-intensive fuels like coal and unconventional oil, but also low-carbon energy sources.”
Again, the basic premise here is false. Technological progress will result in less fossil fuel development, not more. The collapse of coal demand is already well underway in the wealthy countries of the Global North, and all fossil fuels in all countries will follow suit as clean technologies rapidly disrupt the energy and transportation sectors over the next two decades.
The SSP2-4.5 scenario assumes that, “The world follows a path in which social, economic, and technological trends do not shift markedly from historical patterns.” But the authors of this scenario do not understand what those historical patterns of technological change actually are.
As our research at RethinkX has shown, the pattern throughout history has been an S-curve of rapid technology adoption over the course of just 20 years or less once new technologies become economically competitive with older ones–as is now the case for clean energy, transportation, and food technologies. The data throughout history simply does not support the assumption that the shift to new, clean technologies will be slow and linear between now and the year 2100.
The SSP1-1.9 scenario, “sustainability”, is allegedly the most sustainable, but this too is based on false assumptions–namely that lower material, resource and energy intensity are necessary for reducing environmental impacts, and that they are compatible with increasing human prosperity. Neither is true. The solution to environmental impacts is not less energy, transportation and food. That would be like thinking that if your house is on fire, the solution is to extinguish some of the flames. That’s madness. The solution is to put the fire out, which means switching rapidly and completely to clean energy, transportation and food.
If we want to be truly sustainable, we must have a superabundance of clean energy, clean transportation and clean (i.e. non-animal-derived) food that slashes our environmental footprint and gives us the means to restore and protect ecological integrity worldwide. Any attempt to mitigate our ecological footprint by reducing economic prosperity would be disastrous because the scale of cutbacks needed to have any significant effect on sustainability would be utterly catastrophic to the global economy and geopolitical stability.
It is worth stepping back a moment and recognizing that the RCP and SSP scenarios make quantitative projections to the year 2100. This in itself is flatly preposterous.
Five thousand years ago, you could have made a reasonably accurate prediction about what life would be like 80 years in the future. After all, not much changed from one generation to the next. Your children’s lives were likely to be very similar to your parents’ lives.
Five hundred years ago, in the year 1522, it would have been considerably more difficult to make an accurate prediction about life 80 years hence. The invention of the moveable-type printing press by Johannes Gutenberg 80 years earlier in around 1440 had helped turbocharge the Renaissance, setting the stage for the Scientific Revolution. Life in 1602 was still quite similar to life in 1522, but an explosion in the growth of useful knowledge was laying the groundwork for massive social, economic, political and technological transformations to come.
A century ago, in 1922, it would have been very hard for anyone to predict with any accuracy what the world 80 years in the future, in 2002, would be like. Nobody could have imagined the role that nuclear weapons or computers or the Internet would play in our lives, for example.
Today, it is absolutely impossible to predict in any detail what the world will be like 80 years from now, around the year 2100. The rate of technological change is so fast now that our team at RethinkX never makes any quantitative forecasts more than 20 years into the future, because to do so is undisciplined in the formal sense. And technological progress is only accelerating.
Although we cannot know what the world will be like in 2100, we can say that it is implausible to presume the conditions and constraints of today will continue to hold. And this is why we can say that all of the RCP and SSP climate scenarios are implausible: they all presume life in 2100 will be more or less the same as today–still governed by material scarcity, regional resource conflicts, food insecurity, demographic transitions, health and education challenges, and even fossil fuel use. None of these makes even the slightest sense in the context of technologies that we fully expect to see from mid-century onward.
So, what happened? Why did the RCP and SSP climate scenarios get technology so wrong?
At least part of the explanation for fundamental errors and misunderstandings around technology we see in the RCP and SSP climate scenarios is that they were developed by a small group of academic authors operating inside an ideological bubble.
One of the features of this ideological orthodoxy is that it holds long-standing anti-technology sentiments dating back over two centuries to the rise of Romanticism and Transcendentalism. On the one hand, the orthodoxy holds that the arc of history ought to be viewed largely through the lens of human behavior and institutions, minimizing or outright rejecting the causal power of technology to shape societies. There even exists a pejorative term, technological determinism, that is used to label and reflexively dismiss any claims that technology has played a key role in steering the course of human affairs across the ages. Yet, at the same time, this orthodoxy holds technology largely to blame for the massive ecological footprint humanity has imposed upon the planet.
It can’t cut both ways. Either technology has enormous causal power, or it doesn’t.
If it does, then that means technology is also the key to transforming our world in positive ways–including achieving genuine sustainability. We don’t see this accurately reflected anywhere in the RCP or SSP climate scenarios because it runs contrary to the anti-technology sentiments of the prevailing orthodoxy.
The climate science community failed to realize the importance of consulting technology experts in the development of climate scenarios. Instead, they made the mistake of relying on conventional forecasts for technologies like solar and wind power from incumbent energy interests such as the International Energy Agency and the U.S. Energy Information Administration. This would be a bit like relying on Blockbuster Video to accurately forecast the future of streaming video, or Kodak to forecast the future of digital cameras, or the American Horse & Buggy Association to forecast the future of automobiles.
The charts below show the laughably poor forecasting track record of the IEA and U.S. EIA.
Note that the unreliability of these two ‘authoritative’ sources was already clear when the Fifth Assessment Report was published in 2014. Would you depend on advice in a critical situation from someone who had gotten things wrong over and over again?
More cynically, it’s very difficult to see how the IEA or U.S. EIA making the same errors year after year for almost two decades could be an honest mistake. At the same time, it’s very easy to imagine that there are powerful incentives for these incumbents to ignore technological change, or even to deliberately troll others about it.
Regardless, trusting the wrong sources and failing to consult actual technology experts was an inexcusable mistake that the climate science community is unfortunately continuing to make.
The future is obviously uncertain, and the further ahead we look, the blurrier the picture becomes. At first, it might seem reasonable to err on the side of conservativism–after all, if you don’t know exactly how the world will change in the future, isn’t it best just to assume it won’t change much from the present? The answer is no, but the reason why this logic is flawed is rather subtle.
There are dozens of major dimensions and countless minor ones along which change can occur, all of which move us away from our present condition. The fact that these changes are unpredictable does not imply that the noise will somehow cancel out and leave us close to where we started.
By analogy, imagine assembling a complex machine like a car. If you don’t follow the exact steps in the exact order with the exact parts, you aren’t going to end up with a working car. And if you randomize the assembly process, you’re going to end up with a useless pile of junk. This is why tornadoes don’t spontaneously assemble new cars when they pass through a junkyard. The reason why has to do with entropy: there are almost infinitely more ways to incorrectly assemble things than to correctly assemble them.
This analogy helps show why any movement through a large possibility space is only likely to take you away from your current position. This is why the future will be very different from the present, even though those differences are unpredictable.
So, how should we deal with all the uncertainty of the future? The correct response is indeed to construct multiple scenarios that chart the general trajectory and broad outlines of possible futures based on plausible assumptions about what might change between now and then. The trouble with the RCP and SSP climate scenarios, however, is that none of them make plausible assumptions about technological progress.
The climate science community has made very serious technology forecasting errors in its climate scenarios, but has so far refused to acknowledge and take responsibility for them. This is a losing strategy.
Failure to admit and correct the technology forecasting errors in climate scenarios plays right into the hands of conspiracy theorists, because the longer we refuse to admit we’ve made mistakes, the more it looks like they were deliberate. These mistakes are too large to brush under the rug, and so there is no painless option here. We either admit we were fools, or we look like we are liars.
Admitting our mistakes and taking the heat for it is the right move. The alternative only indulges the worst extremist narratives that claim the scientific community has deliberately inflated the threat of climate change and misrepresented our options for solving it in order to advance an agenda of more taxation and more government control over private industry and individual consumer choices.
The public needs to be able to trust the environmental science community, and they can’t do that until we come clean about how wrong we’ve gotten renewable energy and other technologies in our climate scenarios. The longer we pretend nothing happened, the more our legitimacy will erode in the public sphere at a time when trust of scientific authority is already low in the wake of the Covid-19 pandemic.
Given the enormous stakes involving trillions of dollars and all of the world’s policymaking, the errors around technology in the RCP and SSP climate scenarios have had serious consequences. They have misled policymakers and the public alike into believing that the only means to solve climate change are punitive–that we must atone for our past environmental sins by sacrificing human prosperity, tightening our belts and giving up our indulgent personal lifestyles. They have demonized the prosperity of the rich nations of the Global North as unsustainable, and condemned the aspirations of poorer countries of the Global South as unattainable. They have led nations to waste time and resources trying fruitlessly to achieve sustainability through austerity, when this approach is hopelessly counterproductive as I have previously explained.
Austerity cannot solve climate change even in principle, let alone in practice. Prosperity has always been a necessary precondition for solving big problems, both personal and collective, so it is the only real path to sustainability as well. Technological progress in general will inevitably play an outsized role in bringing the prosperity we need to tackle major challenges to billions worldwide, and specific technologies like solar power and electric vehicles will give us the tools we need to directly reduce emissions and draw down carbon. The IPCC climate scenarios must reflect these facts so that we can all make well-informed decisions about how best to solve climate change together.
