And One Way To Make Sense Of Them
In America, with Donald Trump’s double-barreled war on science and the environment, the future of saving the planet from the worst ravages of climate catastrophe can seem bleak. From day one a major objective of his administration has been rolling back advancements in clean energy and efficiency made under Barack Obama and Joe Biden.
But from a broader perspective, Trump’s efforts may prove futile — renewable energy is just too cheap — and the possibilities for reaching a carbon-neutral world economy by 2050 are more abundant than commonly realized. In fact, there are nearly 7 trillion ways to do so, as described in a paper published in the journal Science in March. The purpose of the paper was to help people have more say in how we get there, while making the choices clearer.
“There are lots of very complicated models to produce lots of scenarios but none of them take into account people’s preferences for different decarbonization pathways, and so that, in a nutshell, is what we are trying to address,” lead author Nathan Johnson told Random Lengths.
Instead of the standard way scientists and policy-makers think about the problem, using complicated models, the paper updates a decades-old alternative approach focused on specific kinds of activity, called “wedges,” that can reduce global greenhouse gas emissions by 2050 by about 4%. Examples include generating 6.6% of global electricity from wind or solar power, reducing tropical forest loss by 40% compared with historical rates, using electric vehicles for 17% of global passenger land transport, reducing meat consumption by 30% globally, or doubling building insulation to significantly reduce heat loss. All these very different examples have similar impacts.
“An integrated assessment model [the standard approach] is an enormous cost optimization model. It takes in thousands, if not millions, of assumptions about how the world will change in the future and tries to reduce emissions at the lowest possible cost,” Johnson explained. “So it optimizes based on a single objective function, and that is minimizing cost. The wedges prescribed no objective function. No means of optimizing. Rather, they ask humans to optimize. They ask humans what they prefer of all these possible solutions.”
The paper identifies 36 examples that can produce at least one wedge, while some can produce as many as just over four. Just 20 wedges are needed to stabilize the climate by 2050. As a result there are almost 7 trillion different possible ways to achieve the desired result.
A wedge saves 2 billion tonnes of CO2 equivalent emissions per year by 2050. Deploying 20 wedges reduces global emissions by ~80% over 30 years, consistent with the Paris Agreement goal. Shaded wedges (left) show the median share of emissions reductions across integrated assessment model pathways, colored according to economic sectors.
The reason for this approach is straightforward.
“What we should be striving for are decarbonization pathways that are most societally acceptable, and not necessarily least cost, because the two are not the same thing,” Johnson said. “If cost were king, everyone would drive small super-efficient vehicles that are cheap to buy and cheap to run, but they don’t,” he pointed out. “They find value and a premium on having a larger, more comfortable vehicle.”
And it’s not just cars. “Anytime somebody goes into a shop that makes a decision, that’s based on many things other than just cost and I guess we can apply the exact same to climate change mitigation.”
In the extreme, things that may make sense long-term, using cost as the sole guide, don’t always make real-world sense.
“One product of integrated assessment models, for example, in older generation scenarios, was that they produced scenarios with lots of technologies like carbon capture storage, bioenergy capture and storage, which reduced costs in the far future more than other technologies,” Johnson said. “But unfortunately those technologies have some pretty important ramifications, in the case of bio-energy storage, for the natural world.”
The wedge approach was first introduced in a 2004 paper, but it’s not well-known outside academia. “I first heard of the wedges framework when my co-author, Iain Staffell, introduced us to it in a masters lecture some 8 or so years ago,” Johnson recalled. “It’s been used in classrooms and schools and universities to educate people about climate change mitigation.”
The original framework identified 15 wedges, with seven needed to achieve net zero. The more refined modernized version that Johnson developed has 36 wedge strategies that fall into five broad sectors: electricity (eight), land use (12), transport (seven), buildings (three), and industry (six). Since some strategies can produce multiple wedges, the numbers possible are larger than indicated, but all possible wedges can’t be possible at once because of physical limitations and interaction effects. In part because such limitations are strongest within a sector, it makes sense to consider them distinctly for some purposes.
The wedge strategy presents individuals with an organized framework for choosing from a vast range of possibilities, and is supported by an online tool that allows users to construct their own preferred pathway. But it doesn’t address the next necessary step of collective decision-making. Yet it seems to suggest a next logical step. The 2019-20 French climate assembly was organized into working groups on five issues to produce concrete proposals: food, housing, employment, transportation and consumption. So it would seem straightforward to replace these with the five wedge sectors, and use the same process to arrive at a shared decision of what wedges to choose.
When asked, Johnson was enthusiastic. “I think that’s an absolutely fantastic idea,” he said. He was already working with graduate students speaking to experts to get their views on which set of wedges to choose. “Similarly, people are going out and talking to the public,” he said, with the goal of “trying to synthesize all of those different viewpoints,” which is conceptually a main goal of the climate assembly.
But formalizing the process, making it public and ensuring a representative sample of the public is involved can help further the larger goal of getting broad public support for the selection of wedges decided on. And it could lead to government action. Each working group could prioritize the wedges in its sector, and then the whole assembly could decide on the balance of wedges to be used from each sector.
For a better idea of how this could work, Random Lengths asked Johnson to summarize the constraints each working group would have to consider.
Wedges By Sector
In the electricity sector, “If there are a maximum of 50 wedges achievable in the power sector, but potentially 23 wedges that could be achieved by deploying all of the things to their max, well, we can’t deploy all of those things, we have to choose,” Johnson said. Running lectures three times a year with students construct their pathways, “people tend to favor renewables, but then you also have people that advocate for carbon capture and storage,” but a broader public might choose differently. It’s worth noting, however, that Texas leads the nation in windpower generation because of a citizen assembly process run all the way back in 1999.
The land sector has 12 strategies with 18 total wedges, and no de facto limit. “Land theoretically has enormous potential because you can continue sequestering carbon just by growing more trees or growing more grassland or restoring more peatland,” he said. The main constraints “are just the land availability.” For example, “The more forest you plant the less land you have available for growing food.” But there are wedges for just adding trees to tropical and temperate pastures and to tropical and temperate croplands. And just reducing food loss and waste can produce two wedges, while eating less meat compared to the global average can produce another three.
In the transportation sector, there are 7 strategies, with 11+ total wedges, and a practical limit of 6-10 wedges. “The constraint now is basically how many fossil fueled vehicles you have.” Johnson said. “You can’t get rid of more than all of the fuels that were projected to burn.” But here there are also clear indications of different priorities. In the developing world, people are moving more away from public transportation, while “In the developed world you see more people actually shifting towards public transport in some places, as it becomes more efficient and easier to use,” Johnson noted. “China’s a really good example, building thousands of kilometers of high-speed railway.”
In the buildings sector there are 3 strategies with 4 total wedges, but a practical maximum of 1-3 wedges. “The key constraint is how much fossil fuels we’re currently using in buildings,” Johnson said. Wedges can be gotten by installing heat pumps and clean cookstoves, as well as by reducing building heat transfer.
Finally, industry has six strategies with 12+ wedges total, and a de facto maximum of 11. The constraint on how much can be achieved “depends fundamentally on how efficient we are with material and energy uses, how much fossil fuels are being used in 2050.” Johnson said. Decarbonizing cement and steel production can produce one and two wedges respectively. Producing clean hydrogen can produce four wedges. Reducing oil and gas methane emissions can produce two wedges, while reducing refrigerant emissions can produce one.
Summing all these up, the total number of wedges possible total at least 51, more than double what’s needed. Despite current conditions — including Trump’s war on all things climate related — this suggests enormous cause for optimism. Building a consensus pathway to stabilize the climate by 2050 is clearly an achievable goal. The main barriers in practice seem to be economic and political — organized actors (primarily, but not solely the fossil fuel industry) with immediate benefits at odds with necessary change benefiting all of humanity. So overcoming that is a prime concern.
“You have to have a combination of bottom-up and top-down.” Johnson said. “You need strong climate policy, national, international climate policy pushing from the top down, but also you need consumer action pushing from the bottom up. I think the wedges show how effective both of those things can be,” he argued.
“It’s very difficult for an individual to go out and build a one or two megawatt wind turbine in their back garden. It’s something that has to be driven by energy and utility companies, guided by government policy,” he noted. “Conversely, you have really strong opportunities for individuals when it comes to dietary or other behavioral change, or when it’s a unit-level technology change, buying an electric vehicle or buying a heat pump.”
Wedges At The State Level
It’s a global problem, but the wedge approach can also be applied at the national level — as the example of France’s climate assembly suggests — or even at the state level here in California, where we have the fourth largest economy in the world. To do so requires a few adjustments, Johnson explained.
“Firstly, the size and scale of the wedge has to change,” he said, though how to do that — by what combination of population size and economy — could be subject to debate. Next, “The selection of strategies changes. Some strategies won’t be available in certain regions.” Nothing regarding the tropics applies in Canada, for example. There are, of course, indirect and spill-over effects. In the latest revision of California’s Low Carbon Fuel Standards, for instance, impacts on tropical deforestation were among the issues raised by environmental justice advocates.
Next Johnson said, “You are fighting against different levels of what we would call baseline ambition, what’s already going to happen.” An extreme example is Britain. “They’re already targeting net zero emissions in 2050 and so a wedge framework is not redundant within that scope, it’s different,” Johnson said. It can serve to assess progress. “Do you like the way the government is decarbonizing or do you not?”
With all this in mind, there’s a lot to recommend the idea of convening a California Climate Assembly using the wedge framework to establish a comprehensive state climate policy that could then serve as a model for others to follow. California likes to think of itself as a leader in policy generally, and on environmental matters in particular. More than a century ago, we led the way in introducing the initiative process into American state politics. A state climate assembly would be a much-needed way of breathing new life into that leadership reputation, while taking on the most daunting challenge facing humanity in the 21st century.