Climate 201: Project Drawdown’s Climate Solutions

Author’s note: In 2020 I started publishing a series of podcast episodes under the title of “Climate 201”. The idea was to introduce topics in climate change, climate science, and climate policy — which I’ve studied for some years as a student- and explore them — and their implications — in much more detail than the simplistic framings you often see on the news. Ideally in the process I wanted to answer any questions that my audience had about climate change. By the end, the interested layperson should be up on some of the jargon and nuances of the discussion surrounding climate change. In this series of episodes, we went through some of the solutions proposed and discussed by Project Drawdown as a means of illustrating some of the major ways we can reduce greenhouse gas emissions.

You can find all of the episodes in the Climate 201 series here.

What On Earth is Drawdown?

Hello, and welcome to this episode of Climate 201.

When I first mentioned that I was going to do a series of episodes on climate change, and asked my audience what they would like to see, one of the pieces of feedback I got was that people were keen to hear about solutions to climate change, as well as just the science of the problem.

So this is part of my motivation for talking about Project Drawdown, which is essentially a project — that began with a book — which is trying to get people to focus on some of the practical changes, across various sectors, that we can take to reduce the impact of climate change. You can visit their website at drawdown.org, which has more detail, as does the book, but we’ll talk about some of their research here today.

What I like about Drawdown is also what I liked about one of the better books on climate and energy issues written, which is David Mackay’s Sustainable Energy Without The Hot Air… which is that it’s simple analysis, really, but it does make things at least somewhat quantitative.

The reason that this is important is that, all too often, we don’t ground our discussions on this kind of issue in quantitative terms, but instead focus on qualitative things, visible issues instead.

David Mackay, back in the day, was frustrated by campaigns that urged people to unplug their mobile phones so that little standby lights weren’t wasting electricity.

In his book, he quotes a political party’s manifesto which said that “if everyone in the country switched off their mobile phone chargers, it would save enough electricity to power 66,000 homes.” That sounds impressive, but only because you’re multiplying by the 60 million people in the UK. When you look at it as a percentage, it’s half of one percent of household electricity consumption. In other words, it’s barely worth thinking about in your discussions. “Every little doesn’t help… if everyone only does a little, we will achieve only a little.”

The focus on these incremental or symbolic gestures, rather than structural or systemic changes, has long been a concern for environmentalists. After all, if all my electricity is coming from renewables rather than fossil fuel power plants, the CO2 emissions from my electricity consumptions will fall by 90–95%, and the half of a percent from mobile phone chargers is irrelevant.

You would hope that a good communications strategy would at least focus on the areas which have the biggest impact first, but many do not. Yes, turning off mobile phone charges is using energy more efficiently. But it’s totally irrelevant compared to, say, getting better insulation on your home.

This is a broader theme. One of the most educational infographics I’ve seen detailed the UK governmental budget, in terms of income and expenditures. For all the discussion about benefits that go to the unemployed, foreign aid to other countries, or the money that used to be paid as a membership fee to the EU, you might think that they represented a large chunk of the budget. When these figures are expressed in millions and billions, it can sound impressive. But the reality is that unemployment benefits account for 0.4% of UK government expenditure, foreign aid just 1.2%, and EU membership was just 1.1%. All of post-secondary school education (post high-school) accounts for 0.8% of the budget. Pensions account for 17.1%, while Defense accounts for 6.4%.

How many of these numbers would you have guessed in advance? I would probably have overestimated the military and pensions budgets, and underestimated the amount that is spent on technical and managerial staff in the NHS.

A study in 2014 showed the gap between people’s perceptions and reality. For example, on average, UK citizens thought that the contribution for EU membership was 7% of the budget, when it was actually 1.1%. This obviously illustrates some of the consequences here in terms of our quantitative misperceptions. Regardless of whether or not you think Brexit was a good idea or a bad idea, the fact that the nation on average was out by a factor of 7 on how much the membership cost presumably has some impact on how they voted. Similarly, people overestimated the aid budget by a factor of 5, and underestimated the healthcare budget by a third — because the public perception is that we spend lots of money on foreign aid, and that the NHS is chronically underfunded.

The point here is not to say that people are stupid not for knowing these numbers. The point is that the discussion is almost always qualitative and focuses on certain issues regardless of how important they actually are. These figures are hardly ever discussed. And something similar often happens with the environment.

Mackay’s book came out in 2007. Yet this inability to think quantiatively is pervasive even to this day. A recent survey by a company in Germany gave people a list of actions they could take to reduce their personal impact on climate change. [I don’t actually like the framing of “carbon footprints” too much because I don’t want to overemphasise the responsibility of individuals to solve this issue, but I think this extends to organisations, corporations and governments too to an extent.]

So this survey gave people a list of options to reduce their carbon footprints, as follows:

  • Energy-efficient heating/cooling/insulation
  • Avoid one return trip by aircraft per year
  • Eat less red meat
  • Fuel-efficient driving
  • Buy local and seasonal produce
  • Unplug unused electronics to stop standby
  • No more plastic bags

22% of people suggested that reducing plastic bags was the key — more than picked any other option. This is, of course, largely due to the massive media campaign around plastic bags, plastic waste, and plastic straws in recent years. This has lead people to massively overestimate the impact that this has. Total elimination of plastic bags would reduce the carbon footprint in Germany by just 3kg per person, while the energy efficient heating and insulation would reduce the footprint by 770kg per person — it’s over 200 times more important.

There are obviously other reasons to get rid of plastic waste, not least its other environmental impacts. But the fact that so many people overestimate its impact on climate shows you that our communication on these issues needs to be more nuanced and more quantiative.

So this is why I like Drawdown. You can argue with its methodology and pick holes in the way that they come to the numbers that they come to — and believe me, there’s plenty of academic literature on coming to each of these numbers, and you are always going to lose some nuance and bury an awful lot of assumptions about how these technologies and methods can and will be deployed, and so on. You can’t take an analysis like this as gospel, then.

But it provides a starting point for the kind of quantitative discussion that we really need to have to figure out which solutions need to be prioritised, for companies, for individuals, for governments, and what we should be talking about predominantly, and some of the solutions considered are surprising. And if we’re talking about the assumptions behind these figures, then we realise the true scale of the action that’s required — for example, this is the CO2 saving we get if every farm in the country adopts this new type of pasture, and so on.

So I will talk about some of the solutions in more depth, in order of how Drawdown ranks them. If we keep all these caveats in mind about how the precise figures and ordering can be disputed, and bury some assumptions, we can have an interesting discussion about solutions.

So looking at their “scenario 2”, which aims to keep global warming below 1.5C, they rank solutions in terms of “tonnes of CO2 equivalent that are avoided or sequestered.” between the years of 2020 and 2050, by which point we’d be pretty close to net zero in these scenarios. Everything that we talk about in this series, then, is going to be in terms of changes that we can make over the next thirty years — and, as I’m sure you’ll appreciate, over the next thirty years we are going to have a hell of a lot

Note that the CO2 equivalent metric is trying to take into account different greenhouse gases, including methane, and of course there are some subtleties to how you can do this — see our episode on greenhouse gases for a more in-depth discussion of that. And I just want to briefly overview some of the top solutions here, but it’s worth pointing out that they have “Technical details” and documents prepared for each of these on their website which goes into a little more detail about how the figures are arrived at.
We’re going to talk about billions of tonnes, or gigatonnes, of CO2 here, and I realise that these figures aren’t always totally transparent. So a good rule of thumb to bear in mind is that our emissions at the moment are around 40 billion tonnes of CO2 a year, and that’s maybe 55–60 billion tonnes of “CO2 equivalent” when you include methane, nitrous oxide, etc. So these are good figures to keep in mind when looking at the scale of these impacts.

The top ten solutions, then:

At #1 we have onshore wind turbines, which they estimate could avoid between 47–147GtCO2. The initial investment they estimate that would be needed to deploy wind turbines on this scale would be around ~$1trn globally, but they also estimate that over their lifetime the wind turbines would account for between $4–10trn of operational savings. They note that with costs falling all the time, the costs may well end up being an overestimate for onshore wind, but that it’s important to use the land surrounding the turbines for something practical (like grazing land for agriculture.)

At #2 we have large-scale solar photovoltaics, which they estimate again will save between 42–120GtCO2. By 2050, Drawdown’s book forsees solar PV making up between 20–25% of the world’s electricity generation mix. And again, upfront investment of $3–5trn is needed to make this happen, but in the long run, operating these power plants without fuel is much lower levelized cost than fossil fuels in many locations, and their estimates again suggest between $13–26trn would be the worldwide lifetime operational savings from these projects if this investment is made.

So it’s no surprise that solar and wind do come right at the top of this list. But it’s worth pointing out that the large uncertainty in how much CO2 can be avoided owes to uncertainties about what happens in the other sectors of the economy, even as solar and wind are deployed more extensively. To get up to the maximum end of that CO2 saving, you need large fractions of the demand-side to be electrified, using electrical power that can be generated renewably, and you also need sufficient transmission and storage infrastructure to be built in support of that.

At #3 and #4, we see the impact of what we eat on greenhouse gas emissions. #3 is about reducing food waste. According to Drawdown’s research, a third of the food that’s currently produced ends up never being eaten, which accounts for around 8% of global CO2 equivalent emissions. This is obviously scandalous in a world where we still have hunger and starvation, but it’s bad for the climate too, because all of the energy consumed in producing that food is effectively wasted — and, because agriculture drives deforestation in a lot of cases, there’s additional deforestation that happens purely to produce wasted food. Also, if this food goes to landfill, the bacteria that break it down are often also sources of methane.









So the solutions here are pretty obvious. In lower-income countries, we need to invest in better transportation and refrigeration infrastructure, which prevents food from spoiling before it can reach any end consumer — typically in these countries that’s the biggest problem. And in higher-income countries, the main culprit are households and end consumers, who waste 35% of the food that we consume. So… we need to stop buying food we won’t eat and end up throwing out, and if food isn’t going to be eaten, we need to find better ways of dealing with and processing it. That’s the long and short of it. By far the largest impact on CO2 emissions from this is in the deforestation that we get to avoid by reducing the land footprint of agriculture. Drawdown estimates that between 50–75% of food waste is avoidable, which seems eminently true to me if households genuinely waste nearly a third of the food that they end up buying.

At #4, we have another often-discussed problem, which is switching to plant-rich diets, which Drawdown estimates could avoid between 65–92 GtCO2. Here, about a third of that comes from avoiding deforestation, while more simply comes from no longer having cattle and sheep that produce methane in the quantities that they do. So their definition of this “plant-rich diet” is around 2250 calories a day, and no more than 50g of red meat a day. That’s actually quite generous — should the mood take you, you could have a burger every other day, or perhaps a couple of steaks a week. Substituting red meat for white meat and plant equivalents is obviously the way to go here.

In this, the world is currently very much trending in the wrong direction. As nations like China get richer, we see that they are increasingly moving to diets that Westerners have enjoyed for decades, with increased meat consumption, which is driving these agricultural emissions higher.

Now I realise that this is a very contentious topic, and Drawdown also acknowledge that the behavioural and cultural inertia that comes with eating as much red meat as we do, and this very large industry that depends on red-meat eating, is perhaps even more difficult than the inertia that we have to consider in other systems. Replacing power plants at least requires only a few different actors, whereas getting 50–75% of the world to ascribe to a plant-rich diet requires you to convince a great many more people to change their behaviour.

If I can speak personally on this for a bit. In some ways my situation is pretty unique. Towards the end of 2019, I developed a health condition that essentially makes it impossible for me to eat solid food [you might remember that there was a break to the podcast at the time.] At most I can eat a quarter of a normal meal at any one time.

Effectively, then, this has — pending treatment and surgery — forced me into a switch of diet that’s almost entirely liquid based. Meal replacement shakes, juices, and milk to keep the calorie content up. So, effectively, I’ve become an involuntary vegetarian.

Obviously I would not recommend this to anyone, and frankly it’s been a real struggle for me, and I must also admit I have no idea whether the quite heavily-processed pea and soy proteins that now make up much of the part of my diet that used to be meat are really any better for the environment than meat would be. I’d much prefer to eat a more natural diet if it was possible. But one thing that I will say is that this has made me very conscious of what I’m consuming. I’ve kept a food diary to try and make sure that I’m not running up deficiencies of any vital vitamin or mineral and getting enough calories and so on.
That, I would recommend to everyone. Knowing and planning what you eat is a much easier step than immediately switching from a lifetime of eating meat to vegetarianism and veganism. I’m not in a position to shame people for not being vegetarians, and I don’t think it’s productive to do that. But making these decisions with climate in mind is always helpful.

Next up in Drawdown’s list, at #5, is a solution entitled “Health and Education”. So, essentially, this is making education free and universal, especially for girls, and investing in resources for family planning and access to contraception and so on. Not only would this increase people’s general understanding of climate issues and ability to adapt to climate change, but of course the main lever that’s being driven at here is a question of population. Specifically, they estimate that if these investments are not made, there could be an extra billion humans on the planet compared to the UN’s central projection of 9.7 billion by 2050. They suggest that as much as 85GtCO2 could be saved by these measures between now and 2050.

I think it’s worth noting here that there’s a very disturbing trend in some quarters towards talking about “overpopulation” without appreciating the factors that drive rapid population growth — which tends to be strongly linked with poverty and patriarchal societies where women do not have rights, access to independent education or incomes, or access to reproductive healthcare. So anyone who even begins to mention “overpopulation” as the problem when it comes to climate and the environment had better have an agenda that focuses on women’s rights and alleviating poverty… or you know that what they’re actually after is something vastly more sinister and much, much less effective at actually tackling problems surrounding the environment. Drawdown is keen to note that encouraging this is primarily about justice and equality, and any benefits to the environment are really side effects, and I’m inclined to agree with that.

This isn’t an issue to shy away from. But, at the same time, pretending that the problem is millions of people whose CO2 emissions are comparatively tiny compared to the vast majority of people listening to this podcast is obviously unjust, and another example of the lack of quantitative thinking that can plague these issues.

The next solution, in at #6, is restoring tropical forests. We think about climate in terms of CO2 emissions, but land-use change has also been a really important factor historically. What’s happened to our tropical forests and rainforests is nothing short of catastrophic. At one point, tropical forests covered 12% of the Earth’s land surface: that’s now just 5%.

Now clearly if you can restore what’s now degraded and destroyed forests into stable forestry again, you have a substantial contribution to drawing down carbon dioxide, which is then stored in the forest as plant matter. But when it comes to planting trees, again, I think it’s important to remember that our actions really need to be on a truly massive scale.

Tree-planting is extremely popular as a climate or environmental policy. Even Trump supported the UN’s recent “trillion tree initiative”, and a deeply flawed paper which overestimated how much CO2 you could draw down from planting trees went extremely viral a year or so back — maybe you saw it. This is part of a wider trend. Making grand announcements about planting trees is extremely popular, and people want to live in a world where that’s all we really need to do. But a great many tree-planting and forestry restoration promises simply don’t ever get met in reality.

So, to make this more quantitative. Drawdown’s research suggests that each hectare of tropical forest restored could draw down 4.4 tonnes of CO2 per year. Consider that the per capita carbon footprint in the US is around 16 tonnes — so each individual would need 4 hectares of forest. To make the US entirely carbon neutral through tree-planting alone, which is obviously absurd yet somehow is still being suggested occasionally, you would need to blanket the entire continental US plus a few other small countries in rich, dense, lush, tropical forest. So it’s not viable on its own. Realistically, even Drawdown’s optimistic deployment scenario suggests that reforestation could account for around 2–3 Gigatonnes of CO2 equivalent removed from the atmosphere every year over the next few decades. So again, it’s a question of thinking quantitatively here. Optimistic estimates for the fraction of our current emissions that could be drawn down by reforestation, if a concerted global effort is made, tops out at around 5–10% of our current emissions. Should we do it? Absolutely, for all kinds of reasons. Is it enough by itself? Obviously not.

Drawdown suggests that around 300 million hectares of tropical forest could be restored by 2030, which is actually in line with pledges made by the UN. The New York Declaration on Forests actually pledged to restoring 350 million hectares of tropical forest by 2030. If this was done, Drawdown estimates that between 55 and 85 gigatonnes of CO2 could be drawn down between now and 2050.

The dark side of this, obviously, is how much progress is actually being made on this front. The New York Declaration on Forests was endorsed in 2014 and set these goals for 2030. They did a five year progress report in 2019. The report is subtitled “A story of large commitments yet limited progress”. People have said I have a dry sense of humour. When the phrase “limited progress” appears in the title of your progress report, I would suggest it tells a story.

So what has actually happened in the years since that declaration? Deforestation has actually accelerated. For example, its first goal was simply to cut the rate at which we were losing tree cover from 22 million hectares a year to 9 million hectares a year. Instead, it increased to 25 million hectares a year along basically the same trajectory from before the declaration. Annual tropical forest lost has gone up by 44% since these pledges were made.
Of destroyed or damaged forests that were pledged to be restored, 170 million hectares were promised, but only 27 million hectares delivered by 2020. The report also estimated that annual tropical deforestation was causing CO2 emissions equivalent to the entire European Union.

The point here is that we have had decades of grandiose promises about afforestation to save or restore natural habitats and help to tackle climate change, and instead the situation with deforestation is only continuing to get worse. All of the drivers and economic incentives to clear tropical rainforests and replace it with cropland or land to graze cattle are still there, with agriculture providing 15 times more funding than is allocated to forests. And developments since this report was compiled, such as the rise of Bolsonaro in Brazil who has promised to exploit the rainforest as much as possible, have hardly made the picture seem any better.

For this reason, preserving and restoring tropical rainforests should be a major global priority. But it’s hard for me to be optimistic that this is reasonably going to contribute a lot to climate mitigation when, as things are presently, we can’t even slow down deforestation, let alone stop it. That’s why claims and promises about tree-planting often leave me exasperated. You have to actually bloody well do it rather than just talking about it.

What’s worse is that we can also often see perverse incentives taking place when this type of policy is implemented without care. The vast majority of my audience, like me, lives in the wealthy West where we are insulated from our relationship with the land that’s required to sustain us. But the way in which it’s used, owned, and dealt with is complex. Take the Reducing Emissions from Deforestation and Degradation REDD project that the UN started in 2005. The idea was to add a price signal into the market which reflected the environmental cost of cutting down trees, which emits CO2 into the atmosphere. Because of how this was implemented in some regions, there were often inequitable results. In Kenya, the government evicted 15,000 indigenous people from their lands on the basis that their farming practices contribute to deforestation. In other cases, land grabs are occuring where corporations and states buy up forests to get these payouts for refusing to cut the forests down. And in other REDD projects, the original forests can be cut down providing new ones are planted elsewhere, even though the science shows us this is replacing a resilient and diverse ecosystem, alongside a resilient store of carbon dioxide, with something much less reliable and much less natural. In this way we have seen perverse incentives show up from even well-intentioned policies.

And once again, it is worth noting with all of these “nature-based solutions” one thing. Inherently, it may seem far better to “naturally” remove CO2 from the atmosphere by changing agricultural practices or planting forests, rather than building machines like direct air capture units that do much the same thing. But you have to acknowledge that relying on Nature Based Solutions to draw down billions of tonnes of CO2 from the atmosphere a year would also entail shifting a large portion of the burden of mitigating and reversing climate change to a lot of developing countries, where the land is, and where these solutions would need to be implemented. So again, you can question the equity and justice of relying on farmers in poorer countries to change their normal practices so that those of us in the West can continue to drive around in SUVs, fly abroad on holiday, and buy and use things that we don’t need.

This, of course, is part of a much wider debate surrounding how to deal with the environment in a world run by economists and financiers. If you put a dollar value on the rainforests, you’re arguing that it’s acceptable to destroy them for the right price. If you don’t, the market may well value them at zero (or less than zero, because profit can be extracted from their destruction) and destroy them anyway — as we’ve found, as afforestation continues apace.

You see that again, the solutions posed by Drawdown are all interconnected with each other. This preservation and restoration of forests would be easier if people ate less meat and wasted less food — and, arguably, all of these changes would be substantially easier if we had institutions and organisations in power that prioritised avoiding waste and environmental degradation over wealth accumulation.

Next episode, we’ll go over some more of the solutions dealt with in Drawdown.

Thanks for listening to this episode of Physical Attraction’s Climate 201 series, etc.

Drawdown II: Refridgeration, Electrification, Alternative Technologies [TAPED]

There are a few more solutions from Drawdown that I’d like to highlight. One thing that Drawdown likes to draw attention to is their solutions surrounding refridgeration. Between better management of refridgerants and use of alternative refrigerants, Drawdown suggest that around 100GtCO2 equivalent could potentially be avoided.

Listeners might remember from our episodes on greenhouse gases that the refrigerant gases like HFCs and so on are very very potent at trapping heat in the Earth’s atmosphere — so even though they are produced in comparatively small quantities industrially compared to CO2, they can still contribute quite a bit to warming. In that episode we discussed that there are quite a lot of disputes surrounding precisely how you rank all of these different greenhouse gases. I won’t get into that again here, except to say that obviously the estimates of how important these gases are will be quite sensitive to where you fall down on that side of the argument. But what’s interesting in this is that Drawdown estimates the impact on climate from mass deployment of solar photovoltaics is actually pretty similar to that from these changes to the gases that we use to refrigerate products. It also ranks alongside the contraception, education and family planning regimes that could avoid nearly a billion births, and potentially higher even than restoring the tropical rainforests in terms of climate impact. Yet how often do people talk about this as an important part of what we have to do to tackle climate change? It’s another example of where trying to get these quantitative measures can be helpful to point out where more emphasis is needed.

The good news is that there is some progress being made here. The Kigali amendment to the Montreal protocol is working to outlaw HFCs, starting with high-income countries in 2019 and moving to a global ban by 2028, replacing them with natural refrigerants. Dedicated listeners will remember that we did an episode a few years back in the TEOTWAWKI series, “Lessons from Montreal”, which tried to discuss why it is that the Montreal protocol to fix the hole in the Ozone layer was a relatively easier international treaty to negotiate than global, binding regulation on greenhouse gas emissions. If the Kigali Amendment is fully implemented, it could avoid up to 0.4C of warming over this century compared to the scenario where we do nothing to regulate HFCs, so this is obviously a pre-requisite if we’re to have any hope of satisfying the Paris Agreement and keeping global warming to below 2C.

But ensuring that all of the HFCs and CFCs are currently in equipment that’s out there or being built at the moment are recovered safely and disposed of properly is vital. There are procedures that can do this, but obviously it’s quite a specialist job to dispose of these gases. So right there on the front-line of our fight against climate change is anyone who’s disposing of any air-conditioning units or refrigerators. We salute their efforts!

There’s a historical aside that I can’t really resist here which a lot of people do like to bring up. The predominant technology in modern refrigerators that requires these gases is based on cycles of compressing and expanding the gas in the fridge. You essentially have a fluid, the refrigerant, which floats around a cycle of evaporating and condensing at different pressures and temperatures, drawing heat away from the contents of the fridge when it evaporates.

In the 1930s, Einstein and fellow physicist Szilard actually worked on the design for a different kind of fridge that would have no moving parts, and could use instead the compression of gases like ammonia which are far less damaging to the environment.

You might remember that Einstein and Szilard were the same physicists who sent the letter to President Roosevelt which warned that the Nazis might try to develop an atomic bomb, which led to the establishment of the Manhattan Project… so it might seem strange, given how pivotal this was to world history, that one of their other side-projects was a new type of fridge. Reportedly they were inspired to pursue this design after hearing of a leak from an early fridge that released the toxic refrigerant gases and killed a family in Berlin. So at the time, this wasn’t motivated so much by the desire to avoid using gases that might harm the ozone layer or cause global warming, but instead to get rid of the compressors in traditional fridges which could burst or explode under the wrong conditions.

Quoting from the book Caesar’s Last Breath by Sam Kean on the specific operation of this fridge:

“In the simplest type of absorption fridge you start with two liquids mixed together in a chamber, the absorbent and the refrigerant. The key to the design is that, at low temperatures, these substances mix readily. But if you raise the temperature — usually by warming the chamber with a small methane flame — the refrigerant boils out as gas, leaving the absorbent behind.

The refrigerant gas now goes on a long and tortuous journey. It first flows into tubes behind the fridge and dumps the heat it absorbed from the flame; this step simultaneously cools the refrigerant back into liquid. This liquid flows via gravity into the panels inside the fridge, where it sucks the heat out of the fridge. Absorbing this heat causes the liquid to reboil, and the resulting gas whisks the latent heat away, removing it from the unit’s interior.

Meanwhile, back in the original chamber, the methane flame has switched off, allowing the absorbent there to cool down. A jacket of cold water then cools the absorbent further. The absorbent cools so much, in fact, that when the refrigerant gas finally wends its way back into the chamber, the absorbent condenses it into liquid again and reabsorbs it. You therefore end up back where you started, with a mix of two liquids that you can separate with a flame. Overall, absorption fridges and regular fridges cool things down the same way, by boiling gases. But they use a different process to recycle the refrigerant.”

They eventually submitted 45 patents for this fridge’s design, but the discovery of freon gas which could be used in the other type of refrigerator and was non-toxic meant that the Einstein-Szilard fridge, which was less energy-efficient at the time, was essentially abandoned by major manufacturers.

The point to make here is that there are always these sliding-doors moments in technology development when it’s not clear which road technological development is going to go down. In hindsight, it always seems inevitable and an almost linear progression, but in reality it ends up being shaped by a lot of the decisions that people make along the way. A classic example, of course, would be the electric car. The majority of cars in the 1880s, 1890s were electric, and even by 1900 a third of cars in the US were electric.

One of the classic stories from that era is that of electric car manufacturer Oliver Fritchle, who in 1908 claimed to have an electric car that could travel 100 miles on a single charge. To give you a sense of perspective here, the Ford Focus Electric sold in 2011 had a range of 75 miles, later upgraded to 115 miles in 2017. [Yes, there are Tesla models in 2017 that could do 300+ miles — the point is that it’s pretty astounding that at least in terms of range, an electric car made in 1908 could potentially seriously compete with vehicles produced over a century later.]

Fritchle was so confident in his car that he drove from Lincoln, Nebraska to New York City in one, covering 1,800 miles across some dodgy roads over the course of around 20 days. The electric charging infrastructure back then was actually good enough that you could plan such a journey with stops to recharge every ten hours or so.

But a combination of the invention of the self-starting engine, which meant that the hand cranks which were previously used to start engines weren’t needed any more, and the cheaper costs enabled by mass-manufactuer of internal combustion engine cars eventually did for Fritchle Electric. The invention of the Ford Model T, which was the first really mass-produced and mass-manufactured automobile, drove the electric cars out of competition, and even with their recent resurgence they’ve never got close to the share of the vehicle market that they had in 1900. Fritchle himself died in 1951, but when one of his surviving original cars was moved to the Colorado Museum of History, it was still able to drive through the streets of Denver under its own power in 1990.

Ford were initially working on increasing the range of electric cars at the turn of the century. In fact, it was in a high-profile collaboration with Thomas Edison, first announced in 1914 in the New York Times, that Ford talked about the ambition to make an affordable electric car. According to WIRED, though, the project fell apart over a dispute on batteries. Ford wanted Edison’s nickel-ion batteries to be used in powering the car, but they had internal resistance that was too high and made them unsuitable for powering electric cars. They were substituted with heavier lead-acid batteries behind Ford’s back, and supposedly when he found out about this, he was enraged, which helped lead to the project eventually falling apart.
Again, then, you have to consider the sliding-doors moment of history: what if the ICE developments in the early 1900s had not been made? What if Ford had decided to pursue an electric-car strategy instead of going with the ICE? The incentives to develop more efficient batteries and car designs, and a network for charging points, would have been vastly more than they were today. Of course, it’s always possible that the advantages of fossil-fuel cars, particularly when oil is cheap and environmental impacts unaccounted for, would have won out regardless. But maybe humanity would have missed out on a vast source of CO2 emissions and dependence on oil for transportation.

On the subject of electric cars, they also make Drawdown’s list, but the total impact of them is considerably smaller than some of the other options that we’ve considered. They expect between 12 and 15 gigatonnes of CO2 will be avoided by the adoption of electric cars. This is due to the assumption that, by 2050, the fraction of cars that are electric will be around 16–23%. Drawdown notes that according to their calculations, electric cars powered by the conventional grid reduce emissions by 50%, and those powered by renewables reduce emissions by 95%.

These figures vary of course by the make and model of car, as well as the composition of the fuel mix on the grid. You commonly hear objections to electric cars saying, “well, if the electricity is generated by fossil fuels, it’s not actually greener.” This is false, in part due to the increased efficiency of the electrical engines compared to fossil fuels. Life-cycle assessments of the emissions due to cars are a pretty standard calculation in the field, which attempt to take into account all of the emissions associated with manufacturing and using the car throughout its lifetime.

Carboncounter.com has a really cool interactive graphic which plots the cost of a car over its lifetime vs the lifetime emissions of that car, and a couple of major conclusions come from it. #1 is that there aren’t any battery electric vehicles which have higher lifetime emissions than any fossil fuel cars, although there are a small number of hybrids which do have higher emissions than fossil-fuel compact cars. And #2 is that there’s actually pretty close to a linear regression in the fossil-fuelled cars: the most expensive cars are also the most polluting. Obviously a large part of this correlation is driven by gas-guzzling SUVs which are both expensive to run and destructive for the environment, and which are totally unnecessary for the vast majority of people to drive but which have managed to convince millions of us to destroy the planet and our bank balances with some slick advertising and marketing them as a status symbol. So there’s a win for humanity.

So, 16–23% adoption of electric cars by 2050. Could we do better? The UK is hoping to ban new sales on fossil fuel cars by 2035 in line with our net-zero target for 2050. That would mean that presumably the UK’s car fleet would be 80–90% electric by 2050. There are 14 countries who are currently considering similar measures, and China are said to be “researching a timetable” into doing this, which would be a major coup. If these policies actually go ahead, then alongside the increased adoption of electric cars in countries without the ban, we might have a better fraction of cars going electric by 2050. Recent projections (2018) for the US, however, suggest that by 2050 there may only be 22% electric cars in operation.




Again, this is an interesting point on the quantitative impact of different measures we can take. Managing refridgeration better, in terms of recovering these gases and changing technologies, at least according to Drawdown, is almost ten times as important as the anticipated switch to electric cars. On the other hand, it also illustrates how you can criticise some of the assumptions that they make. For example, I would argue that assuming that 22% of the world’s vehicles go electric by 2050 is probably a quite likely outcome even if we don’t make radical changes to encourage electric vehicle adoption… but getting 75% of the world’s population to stick to this plant-rich diet, which would buck current trends, could well be a lot more difficult. Your mileage may vary on that one.

I want to group together a whole bunch of the other solutions that Drawdown discusses into general land management and agricultural methods. I won’t go into too much detail here but will just briefly discuss the ideas. Each of these solutions accounts for around 20–30 gigatonnes of CO2 according to Drawdown. I’m going to be pretty vague here, though, because when it comes to these natural solutions — where the carbon stored is often based on only a few small measurements and relies on pretty hefty assumptions about how vast swathes of the world’s land are being managed — I think the error bars on what you can actually achieve here are pretty large. So these “nature-based solutions”, then:

Silvopasture — that is, you have trees and pasture together, with cattle grazing amidst trees. Having trees on the land that’s agriculturally managed can store substantially more carbon than traditional agriculture, but it’s obviously costly and slow to implement this method. There are co-benefits — the trees can allow the farmers to provide different products, and may also offer some protection from extreme weather conditions — but clearly people would need to be incentivised to do this.

Similar to silvopasture is tree intercropping — planting trees amidst certain types of crop. The advantages here can often include things like the trees preventing erosion, protecting certain vulnerable plants from storms or excessive sunlight, as well as of course sequestering the carbon in those trees. Etc. Depending on what you plant, they can provide a useful extra source of income for farmers in themselves. Obviously this used to be a much more common practice before the rise of industrialised agriculture where most of the trees were ploughed under to give rise to vast farms covering many hectares with a single crop.

When it comes to livestock, you can preserve some of the land that they’re grazing on by cycling them through different pastures, preventing those pastures from being excessively degraded by overgrazing. Similarly, letting animals spread out more will also allow the land they graze to store more carbon. The hope is that managed grazing makes the land more productive in the long run, and thus allows you to — eventually — raise more animals before the land is totally depleted, resulting in more long-term profits. Of course, the issues here are that the economic incentive is basically going to be to pack grazing animals as close together, on as small a plot of land — and to pursue as much short-term profit, even at the expense of long-term viability for the land plot — as is feasible.

Protecting peatlands is very important. Peatland — the types of bogs and mires that Hobbits would trek through probably halfway through the second movie — is made up of decomposing plant matter, and so it’s basically just a mulch made up of stored carbon. According to Drawdown, peatland — which covers around 3% of the Earth’s land area — stores twice as much carbon as the world’s forests. Perhaps up to 500 gigatonnes of carbon is locked up in peatland. When that peat becomes exposed to air, it can oxidise, producing bubbles of CO2.

Luckily for us, peat is generally valued less than wood from forests, and so 85% of the world’s peatland is basically intact. But, much like fossil fuels, it can take many many years to form and just a moment to burn: it can take thousands of years to build up peatlands but only a few for them to be destroyed. But a combination of strong protections of the peatland that exists, fire prevention, and rewetting some of the degraded areas so that they can become sinks of carbon again could save substantial CO2 emissions, alongside protecting a natural ecosystem + the creatures that depend on these unique habitats to survive.

Planting new forests on degraded land is one of the solutions. This clearly increases the sink of carbon in the trees and the surrounding soil, but you need to be careful about how it’s done: simply planting huge forests with a single kind of tree tends to be worse for the environment and lead to less stable forests and ecosystems. [This is not my field but I know there’s a hell of a lot of research here.] A lot of these plantations are pretty unsustainable. A better alternative is to plot a variety of different species that were originally native to the area, trying to restore something that at least vaguely resembles what was destroyed in the first place.
Restoring forests in the temperate zone — i.e. mostly in the Northern hemisphere midlatitudes — is also suggested. 99% of these forests have been altered by human activity in some way, whether converted to timber production, wiped out for agriculture, or disrupted by development. Although the area they cover is much smaller than the tropical forests — and the rate of deforestation is slower now — there are still many millions of hectares that could be restored in the future.

Another solution they suggest is switching some of the crops to perennial crops rather than annual crops. Crops that grow the entire year around — bananas, avocado, breadfruit, nuts etc. — store more carbon than the crops that are harvested each year, but annual crops account for about 89% of what’s grown on cultivated land at the moment. Shifting that balance slightly, by doubling the amount of perennial crops, could also make crops more resilient to climate changes. Some of these crops have a higher yield at a lower cost than the annual alternatives. So the major barrier here, alongside persuading farmers to change, is the market demand for annual vs. perennial crops… which is a little harder to deal with.

Where you do have annual crops, it’s important to manage those with carbon in mind. Green manure instead of artificial nitrogen fertilisers (which produce nitrous oxide as a greenhouse gas), compost and organic production techniques, rotating crops on a regular basis and avoiding tilling the fields can all result in a greater deal of carbon sequestration in the soils — doubling, tripling, or even quadrupling the amount of carbon that’s stored in the soil. This aim for regenerative agriculture is also important for the long-term productive capacity of the soils, which is again being degraded over time.

Bamboo, when planted, can be a rapid way of drawing down CO2 — it can live on some quite degraded land and acts to draw carbon down faster than nearly any other plant. It has uses for humans as food, building material, and paper. It has a similar tensile strength to steel! The only issue is insuring you don’t plant it in areas with other fragile ecosystems as it can prove to be quite an invasive species.
Drawdown estimates that there are nearly 400 million hectares of farmland that has now been abandoned because the soils are too degraded to produce sufficient food. The main issue there is that it can often be cheaper to find new land — e.g. through deforestation or migration — than it is to restore it, which is time-consuming and labour-intensive. But clearly if this is done, it can turn this degraded land from a net source of carbon into a sink, alongside reducing pressures to feed the world.

Rice is a staple food for much of the world, but flooded rice paddies are also a substantial source of methane because of the methane-producing bacteria that thrive in them — this accounts for about 10–20% of methane emissions. Different strains of rice, which don’t require quite as much water, can be planted in some environments, as can different ways of providing nutrients to the rice and draining the paddies in the middle of the growing season. All of these techniques would help to reduce the emissions from the paddies.

So you can see that actually, perhaps a surprising number of the major changes we need to adopt to mitigate our emissions and solve climate change — at least, relative to what people often think about — are to do with the way we grow food, and the way that we manage land that’s under cultivation at the moment. In a world where there’s immense competition for land, some of these potential uses may well conflict with each other. There are a lot of issues to overcome here. There are 570 million farms worldwide, according to a paper by Lowder et al. — and 75% of these farms are run by individual families. That’s an awful lot of people that you have to either convince or incentivise, or both, to change their farming practices, some of which will go back decades, to practices that are more sustainable and better for CO2 sequestration. A lot of these people are hardly making vast sums of money, either — they may not have the resources available to just up and change these practices, particularly if they have to compete with others who might be sticking to the old ways. It’s a lot to ask of a group of people to feed the world and drawdown carbon emissions at the same time. And, of course, we know that the major economic and financial drivers are always often going to point to more exploitative practices as a way of generating short-term profits.

The key, I think, is a greater awareness of the potential of these techniques and the co-benefits that they can offer to farmers and people involved in agriculture. We’ve got to have regulations and an incentive structure that’s in place to deal with this type of thing. Something like Nori, the startup that we interviewed on this show a long time ago — whereby people “buy” carbon credits in exchange for paying farmers to adopt these more regenerative practices — could certainly be a part of the solution.

Sometimes it seems difficult for any of us to really influence this type of policy. After all, you might not know any farmers, or own any land: I know I don’t. This is where a combination of the demand-side measures we can all get involved with: not wasting food, maybe consuming some more of these perennial crops, helping to shift demand towards lower-carbon products by changing our diets, and of course being engaged citizens in our democracy who ask for this kind of thing are going to be our major weapons.

Next episode, we’ll finish our series on Project Drawdown, discussing some more of the practical solutions they propose to mitigate climate change — from energy efficiency to cleaner cookstoves.

Thanks for listening to this episode of Climate 201 from Physical Attraction.
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Drawdown PIII: Cookstokes, Cobenefits, and Conclusions [TAPED]

Another class of solutions that Drawdown look at is energy efficiency solutions. I’m planning a whole episode on energy efficiency, so I’ll save a lot of information for that specific episode, but here we’re talking about things like LED lighting to replace conventional lighting, home and building insulation, high-performance glasses that can help keep buildings at a decent temperature, heat pumps instead of boilers. We’re talking about district heating and cooling systems and combined heat and power systems, where power plants and industrial processes that produce waste heat then channel that heat to buildings in the surrounding area, rather than letting it go to waste. Smart thermostats, more efficient transportation in terms of trucks, cars, planes, boats, and a focus on carpooling and public transit rather than individual car ownership. All of these things allow us to be more efficient in the way that we use energy and that we use fossil fuels to produce that energy.

As I say, we’ll talk much more about efficiency solutions in future episodes (and have done in the past), but one point I do want to make is the point about sexiness. Energy efficiency needs to be a lot sexier than it is. Somehow (and you probably have your own ideas about how and why this is, as do I) we have a culture in the West where we’re obsessed with building new things, massive extravagance, excessive spending. People driving around in ridiculously inefficient cars is an example, but it’s pervasive through a lot of areas that this efficiency is hardly of any concern to people. Even when it comes to climate solutions, there are a lot of people and politicians who are keener to talk about massive development of renewables projects, or far-off prospects like nuclear fusion, than there are people who want to talk about energy efficiency. But at its root, doing things more efficiently is better for the planet, and it saves money. The fact that so much inefficiency and waste remains in the systems that we build and operate is depressing, but the good news is that driving for this gives us nothing but benefits at the end of the day.

And one advantage of energy efficiency is that it does begin at home and in the workplace. There are doubtless measures you can take around your own house that are going to help, from efficient lighting to smart thermostats, and you can also encourage this in the places you spend a lot of time and on an organisational level. We have the practical power to influence this.

One area that Drawdown reccommended that’s quite interesting to touch on is telepresence — avoiding face-to-face meetings and air-travel by investing in remote conferencing and remote meetings instead. COVID-19 has certainly accelerated trends towards doing this, and it may be many years until the number of business trips taken by flights does actually recover. I think this may be one of the more permanent quote unquote “silver linings” from the awful situation in the last couple of years — but it also shows you just how disruptive a shock is sometimes needed for these behavioural changes to take place, because this massive shift to remote working and so on would have been unimaginable prior to the pandemic, and likely much slower as well.




This is actually just a subset of some of the most important interventions that they list — there are over 50 in total — but it does paint a picture of the type of thing that we’re talking about here. I want to briefly talk about some of the things that aren’t considered in a major way, and why.

Firstly, they don’t consider nuclear power as having a particularly big role to play in reducing emissions — in their projections, they expect that nuclear will continue to provide a similar fraction of the world’s energy as it does today, at around 10%. Given that this figure has remained pretty stable across the decades, and if anything it’s getting harder and more expensive just to maintain and replace the nuclear fleet in countries that use nuclear power, I think this is a pretty likely projection, but of course there will always be people who advocate much more focus on new nuclear build. Drawdown takes the perspective that the risks and costs of nuclear outweigh the benefits, and so they choose not to focus on it… but I would say that it’s always possible, particularly if research and development does finally produce next-generation fission reactors that can be built at a lower cost, that nuclear could play a larger role than they envision in the future. But certainly for changes by 2050, the industry is starting to run out of time and lose ground to its competitors.

Secondly, there are obviously some types of renewable power that we didn’t mention here — hydropower, geothermal power, and ocean power from the waves and tides. These do make it into the list of solutions in Drawdown, and they’re all worth developing for their own reasons, they aren’t considered to be major parts of the solution. The reason being that each of these solutions is either too expensive to deploy over alternative solutions, or is geographically restricted so that it can only generate a small amount of power in suitable regions. So in their scenario, geothermal power comes in at around 10 GtCO2, biomass power at 2–3 GtCO2, and similar for waste-to-energy and ocean power.

Also, we have to mention that there are some major investments that will be necessary for a green grid to make sense and for it to be viable — developing energy storage and transmission, alongside flexible consumption of electricity and energy on the demand side. These don’t get ranked as part of Drawdown because they don’t “directly” contribute to CO2 reductions, they argue, but obviously since investing in this kind of thing is a prerequisite for the other solutions to work, it’s a shortcoming of the analysis.

Finally, by and large, although the project is called Drawdown, they’re really concerned with what we would call climate change mitigation — in other words, changing our practices to avoid emissions in the future.

There is, of course, some overlap between what some people call negative emissions technologies, what others call nature-based solutions, and what some people call mitigation. Does afforestation count as negative emissions, or is it more in the realm of restoring what we’ve destroyed? I’m not going to litigate all of these questions, but I will say that because Drawdown is mostly about climate mitigation and nature based solutions, there are lots of negative emissions technologies and negative emissions approaches that they don’t consider. Here I’m talking about stuff like direct air capture, bioenergy with carbon capture and storage, and enhanced weathering, for example.

We’re also going to deal with these in another episode. This list is by no means comprehensive. But I think Drawdown chose to avoid quite a few of these techniques because they don’t really count as mitigation, and it’s also unclear how much of them would be deployed in the cases where the technologies only really exist as small demo plants today.

And, of course, it makes sense to concentrate on these things first and foremost — because the reality is that in almost all cases it’s going to be cheaper to avoid emitting the CO2 in the first place with this kind of mitigation technique over the next few decades than it will be to rely on technologies coming along that can suck CO2 back out of the atmosphere again by the end of the century. So these things really are the last thing you should be thinking about.

The last solution that’s near the top for Drawdown is promoting better cookstove technology. Something like 3 billion people in the world still cook with rudimentary stoves or on open fires. This can contribute to deforestation, but also has very significant health impacts due to things like carbon monoxide inhalation and the pollutants from incomplete burning of wood, particularly in places with poor ventilation. One in six premature deaths is due to air pollution, and in 2010 a report from the World Health Organisation suggested that 2 million premature deaths a year could be attributed to smoke inhalation from traditional cookstoves and fires, mostly affecting women and children. The “black carbon” from biomass burning contributes quite substantially to climate change as well, so minimising this is good if you can manage it.

Part of the issue here is that it’s yet another area where the real, root cause here is addressing global poverty. The reason people use rudimentary cookstoves and open fires is because they can’t afford anything better, or don’t have access to electricity or other alternatives. The cost of buying some new unit upfront is prohibitively expensive for a lot of people. And clearly if you’re cooking on an open fire, you have very low direct maintenance costs, at least in dollars. So to make progress here, we need to provide cleaner, more efficient cookstoves and methods for cooking directly to the people who need them, and preferably either find solutions that don’t cost that much to maintain, or else help pay for the upkeep as well. So for example, Drawdown points to advanced biomass stoves, noting that “by forcing gases and smoke from incomplete combustion back into the stove’s flame, some cut emissions by an incredible 95 percent, but they are more expensive and can require more advanced pellet or briquette fuels.” But obviously if these stoves and these fuels aren’t available, it’s impossible for people to switch. You can read a lot more about this issue with the work of the Clean Cooking Alliance online.

I think it’s worth flagging a couple of things up here that this particular issue brings up, which are common to plenty of individual things that we need to do to tackle climate change, and this is really the reason that I wanted to finish with this solution. The first is that actually, solving a lot of these problems does have significant co-benefits. Cutting down on coal and cars is good for climate, but also good for air pollution. Reducing food waste is good for emissions, but also for food security. We’re continually told we might need to produce food for another 2–3 billion people by the middle of the century; if we didn’t waste what is produced now, there may well be enough for them already; the same is true of better agricultural techniques which will help us sustain the productivity of these soils into the future. Giving access to education for women and girls might have some knock-on impact on emissions down the line, but it also has plenty of other benefits: for equality and justice, for the quality of life of people on this planet, and economically if this is the only lens you want to look at the world through. Moving to a more plant-based diet helps stop deforestation, but it can also have significant health benefits. In other words, there are an awful lot of win-win options when it comes to climate mitigation and plenty of good reasons to do these things anyway.

Which brings us to the second aspect, which is these concepts of inertia and lock-in. We discussed this back in the episodes on green stimulus after the COVID crisis, but it’s important to remember that the reason these changes can’t happen overnight is because a lot of actual work has to be accomplished on the ground to make them happen. To make all of this happen, you have to *do* an awful lot. You need to set up and pay for the schools and the family planning centres. You need to invest up-front to build the solar panels and wind farms. You need to set up the incentives and regulations that protect the rainforests — and you need to do more than just make empty promises about tropical deforestation and planting trees. You need to convince and help three billion people cook with more modern equipment — and people have to physically start making millions of clean stoves! You need to get hundreds of millions of people to stop wasting food and modify their diets some.

All of these things are the civilizational equivalent of going to the gym, or saving that money for the future rather than spending it today, or installing double-glazing. In the long-run, you’ll reap massive benefits for it, but in the short-term, there is a hurdle to overcome: it won’t just happen if left to market forces or vested interests to decide.

And the flip side of this inertia that you have overcome is lock-in. All of these changes involve transforming systems, whether it’s the systems by which we generate electricity, the systems by which we feed ourselves, the systems by which we transport ourselves around. When we’re building these systems, if we build incorrectly, we’re locked in to using that bad infrastructure and it becomes far more costly to change it due to the sunk cost of what’s already been built — making these bad decisions adds to the inertia of the system.

If people stop relying on traditional biomass and wood for heat and cooking, and turn instead to natural gas stoves, that’s going to lock in dependence on those fossil fuels in just the same way that we have done in the West. If people build terribly inefficient new buildings, it locks in that waste for the future and makes it harder to overcome. If people plant massive monoculture crops or forests rather than something more diverse, that’s going to occupy that land for a really long time. If we have a market set-up that demands massive production of corn, or wheat, rather than perennial crops instead, then you have a lot of habitual inertia to shift that — and you have to convince a lot of people to change their behaviour for that to change! As countries around the world start to approach Western levels of energy consumption and economic development, if that’s fossil-fuelled development and consumption, we’re locking in an awful lot of pain for the future. So the keys to Drawdown are changing those systems that already exist that are carbon-intensive where-ever we can, and making sure that anything new we build doesn’t make the same old lock-in mistakes of the past.






So what can we learn from an exercise like Drawdown? As I’ve been at pains to stress throughout, whenever you see this kind of quantitative analysis, you are inevitably going to have some problems with it. It’s very sensitive to the assumptions that you make about how these new things are going to be adopted; if things are done to quite exacting standards, you can achieve these carbon dioxide reductions. But the systems we are dealing with are very complex — and, especially in the case of a lot of the agricultural and soil sciences, there’s still an awful lot that we need to learn to do really good accountancy on how much CO2 is really being saved.

A classic example to my mind is the biofuels standard that was set in the US. The aim of this policy was to say — okay, some % of fuel has to come from biofuels, and this will reduce CO2 emissions from the transportation sector. Estimates, particularly those produced by the biofuel lobby, are obviously going to say that biofuels can be produced cheaply, efficiently, and with a massive reduction in resulting CO2 emissions. But the result of the bioethanol mandate was that the big corn producers in the US invested in corn-to-bioethanol production. In other words, although biofuels were produced and used, because the process of converting corn to bioethanol is inefficient — corn is not a great feedstock for biofuels — the carbon savings were way less than they were projected to be, and in some cases they may have been negligible. But the amount of cropland that ended up dedicated to corn-bioethanol, for questionable benefit to the environment, was massive and has clearly contributed to pressure on food prices.

And the assumptions about how quickly technologies will develop, how much they will be adopted, and how many people are going to go for whatever solution you pick: these will always, ultimately, owe at least a little to subjective opinion. Other people could come up with a completely different set of figures and probably find quite different ways to decarbonise society.

But what an analysis like Drawdown does do is give us an order-of-magnitude, justified estimate that outlines the assumptions we’re making, and that’s a good starting place. It also shows you the full range and breadth of the systems that we will need to transform to seriously tackle climate change. Jane Flegal, a climate scholar, Tweeted as I was writing this script something that seems very relevant: she said that decarbonisation is a problem with physical systems in the world, and not just a modelling problem. Creating better models of how the energy sector, or the agricultural and land use sector, or the industrial sector, or transport can contribute to carbon emissions is clearly going to help us understand what type of policies they want to pursue.

Our failure on afforestation, where so much has been promised and so little delivered, should be an object lesson in the fact that we can’t rely on empty promises. We can’t rely on academic calculations of the technical potential of what various things could do to reduce CO2 emissions and drawdown carbon dioxide if everyone behaves brilliantly and optimally: we need the data from people actually doing this on a large scale. All that a roadmap like this can do is give you a rough idea of what to focus on; the challenges come with actually doing it.

These changes really amount to transformations in huge aspects of the way we live right now. It’s hard to see how to get a plan that adds up to 2C without serious, transformative ambitions that are matched by actions on a similar scale. Especially as the years tick by with continued, inadequate action in all of these areas.

The advantage for us, of course, is that almost all of these transformations don’t just benefit us when it comes to the climate. In many cases, they amount to simply being smarter and more well-rounded in our priorities. In many cases, they are things that we’ll have to do for other reasons — to ensure food security, to prevent premature deaths from pollution, and to prevent energy from getting expensive or unattainable as fossil fuel extraction continues to get more difficult, costly, and environmentally destructive. And as we’ve discussed, the co-benefits of taking these actions generally amount to living in a healthier, more sustainable, safer, and more prosperous world. What else do we need to say? It’s past time we made the change.

Thanks for listening etc.