How to avoid a climate disaster

by Bill Gates

summary by Mikolaj Pawlikowski

Table of Contents

“How to avoid a climate disaster” by Bill Gates
Summary
Chapter: Introduction: 51 Billion to Zero
  • the world typically adds 51 Billion tonnes of greenhouse gases per year
  • to stop warming, we need to get to Zero

Virtually every part of a modern lifestyle contributes to releasing greenhouse gases. If the world carries on like it is, Gates predicts that the effects of the charning climate will be catastrophic. Gates initially started from the angle of delivering affordable energy to the poor, but as he dove into the details, he realised that it also needed to be done without emitting any new greenhouse gases. It’s not acceptable to demand from poorer nations to not use more energy, so the only way forward is to make the clean sources the cheapest option.

Gates also addresses his own ‘absurdly high’ carbon footprint, including flying private planes to a Paris climate conference. He believes that his other actions, like offsetting his family’s aviation emissions will make up for it.

The book will follow five parts:

  • why going to zero is necessary
  • how to have an informed opinion about climate change
  • why going to zero will be very hard
  • why going to zero is possible
  • what steps can we take now
Chapter: Why zero?
  • the earth is warming up due to the greenhouse gases
  • we don’t know exactly what the effects of the warming will be
  • small change in average temperature can have very large effects

As we go about our lives, we produce greenhouse gases. These gases stay in the atmosphere for a long time on human scale (around 20% of CO2 emitted today will still be there in 10 000 years). The greenhouse gases increase the average temperature on earth.

We don’t know exactly what effects the increase temperatures will have, but given the long half-life, the effects will be long term.

By Zero, Gates means “near net zero”, as the scenario where we abandon all fossil fuels immediately is not possible, and we will need to rely on technologies actively removing greenhouse gases from the atmosphere.

Small numbers make big difference: during the last ice age, the average temperature was only 6 degrees Celsius lower, and during the age of dinosaurs, likely only 4 degrees Celsium higher.

Greenhouse gases include CO2, but also other gases which are more potent at warming up the atmosphere, like methane which is 120 times more potent, but doesn’t stay in the atmosphere for as long. So to simplify things, scientists came up with a single measure of “carbon dioxide equivalents”, or CO2e for short.

Greenhouse gases work just like a car windshield on a sunny day. The heat from the sun gets trapped in the car, and the interior of the car gets much hotter than the exterior. Why does it get trapped - it entered through the windshield in the first place, so why doesn’t it go out through it again? This is because the heat reflected back from the car interior is at a different frequency to the one incoming from the sun, and it’s not able to pass the windshield back out.

All life on earth relies on this greenhouse effect - without it, most of the energy coming from the sun would be reflected back into space, and the earth would be cold. The problem stems from us emitting more and more greenhouse gases and tweaking the strenght of the effect.

We know that the earth is warming, it’s about 1 degree Celsius higher than during the pre-industrial levels, and we can predict some broad trends, but we don’t currently have a way to predict particular events, or even know exactly how much the planet will heat at a particular point in the future. We also know that not everywhere will be affected equally - some places will be hit much harder than others, hidden behind the ‘average’ temperature increase.

Gates argues for the rich countries as the place where a lot of mitigation needs to start, not only because that’s where the bulk of the emissions have been done historically, but also because they are best suited to develop the necessary climate solutions in terms of funding, infrastructure and seizing the economic opportunity.

Tags: CO2 methane CO2e net zero greenhouse effect

Chapter: This will be hard
  • greenhouses are emitted in various ways, many of which are not obvious at first sight
  • to achieve a net zero, we need technologies that are better and cheaper than the existing ones

Greenhouse gases are much more pervasive than they appear at first sight. From your toothbrush, made of plastics made of fossil fuels, to the grains grown using a fertilizer which releases methane, to the beef on your burger (cows produce methane), to the transportation and the nearby power plant; they are everywhere.

Fossil fuels are cheap and abundant, and massive industries have grown around them. To achieve net zero, we will not need need breakthroughs in science and enngineering, but also a consensus about preventing a climate disaster being a priority, and the laws and regulations that follow that. And the existing energy systems will need to continue working and accomodate for increasingly energy-heavy lifestyles, while at the same time emitting less greenhouse gases.

To top things up, our timeline is probably shorter than any of the previous gigantic changes that we’ve gone through as a species.

Tags: greenhouse gases

Chapter: Five things to ask in every climate conversation

Without the necessary context, it’s often hard to make sense of the climate change discours. The author offers some tips on how to approch such situations.

First, translate the numbers into a percentage of the 51 billion ton reduction goal. Gates offers an example of a programme promising 17 million tons reduction. To know whether it’s a significant change, just divide it by the total 51 billion tons, the current yearly total emissions.

Second, a comprehensive climate plan will need to address all of the sources of emissions:

  • 31% - building things (steel, cement and plastic)
  • 27% - electricity
  • 19% - food production (plants, animals)
  • 16% - transport
  • 7% - heating and cooling

Thirdly, it’s useful to have an idea of how much power people require. An average American household is in the order of kilowatts (1000 watts); a small town, megawatts (1000 kilowatts); a large city, gigwatts (1000 megawatts); a large country like the USA 1000 gigawatts.

Fourthly, different forms of energy production have vastly different space requirements. We call it power density, or the amount of energy (watt) we can produce from a unit of space (m2):

  • wood & other biomass - 1 watt / m2
  • wind - 1-2 watt/m2
  • hydropower - 5-50 watt/m2
  • solar - 5-20 watt/m2
  • nuclear - 500-1000 watt/m2
  • fossil fuels - 500-10,000 watt/m2

Finally, let’s think about costs. The existing energy technologies are typically the cheapest. The added cost to use a lower emission alternative is called a Green Premium. Considering different ideas, it’s important to look at whether the Green Premium is affordable to everyone. Unfortunately, we don’t yet have alternatives for everything (for example cement), so it’s not always easy to estimate the Green Premiums.

Tags: sources of emissions power density green premium

Chapter: How we plug in
  • making electricty is arguably the most important problem to tackle to reduce greenhouse gases emissions
  • we’re going to need a collection of various technologies working together to achieve a reduction
  • each technology comes with unique advantages and disadvantages, and progress is being made on mitigating the latter

Cheap & reliable electicity is a bedrock of modern life. Generating that electricity produces 27% of the world’s greenhouse emissions.

While manufacturing emits more, the electricity production is arguably the most important to address, because it can be used to decarbonify other activities, and because over 860 million people are still missing access to reliable electricity today.

Two thirds of the electricity generated worldwide today is from fossil fuels:

  • 36% coal
  • 23% natural gas
  • 16% hydropower
  • 11% renewables
  • 10% nuclear
  • 3% oil
  • 1% other

The electricity is remarkably cheap (the USA spends about 2% of its GDP on electricity), in big part because of how cheap fossil fuels have become. Most countries actively work on keeping their fossil fuels prices attractive.

How much would it cost to decarbonify electricty? For some places, like the USA and Europe, the cost appears to be reasonably low. Some studies estimate around 15% and 20% premium respectively.

Unfortunately, other places don’t have the favourable conditions for wind or solar. Africa and Asia are in the toughest spot. Bulding inexpensive coal plants appears to be the most economical decision for many countries in these regions.

A big hurdle to overcome is the intermittency. Solar and wind are intermittent, meaning that they don’t produce the same amount of energy at all times. Obviously, when the sun goes down, the solar panels stop working. This can be solved by using batteries to store the energy, at an extra cost. With the current tech, the storage cost can easily be multiples of the cost of generating the electricity in the first place.

Additionally, there is seasonal variance. Because of the Earth’s tilt, the amount of sunlight any place gets depends on the time of the year. The size of that effect depends on how far you are from the equator. The author gives the example of Seattle, which gets twice the amount of sun on the longest day than it does on the shortest. Now, imagine that you’d like to install solar panels to cover a town’s needs. If you install just enough for the summer, the town won’t have enough in winter. If you install enough for winter, you will overproduce in the summer.

“Transporting” electricity is also hard. Transmission lines are expensive and require a massive investment to modernise. And the USA doesn’t have a single, unified grid - instead, a collection of regional grids.

It’s hard to conceive of a scenario of decarbonising the electricty production without nuclear fission reactors. The high-profile catastrophies like Three Mile Island, Chernobyl or Fukushima are well-know, but statistically nuclear power kills fewer people than any fossil fuel. New designs and companies are working on making nuclear fission safer, including Gates’ own TerraPower.

Nuclear fusion, relying on atoms of hydrogens merging into helium in high temperatures, just like it occurs naturally in the sun. Nuclear fusion holds a lot of premise - the fuel is abundant and cheap, there is no risk of runaway reaction and the radioactive waste is much more easily manageable. However, it’s proving hard to engineer in practice, hence the joke about how it’s 40 years away, and will always be. None of the currently built reactors produce more power than they consume, they’re research devices. ITER in France is hoping to generate excess power in late 2030s.

Offshore wind is another noteworthy technology, allowing for energy production closer to large cities, and benefitting from more consistent off-shore winds. At the moment it produces a miniscule fraction of USA’s overall production (0.003%), but in theory could produce all of it if deployed widely. Getting it approved remains a major challenge, including a labirynth of permits.

Geothermal also holds some promise. It relies on pumping water underground to use the heat in the rocks hundreds to thousands of feet under the surface, and can reuse some of the technologies built for fossil fuels. It has been calculated, however, that in the UK, even if we deployed thermal to every square feet of the country, it wouldn’t cover the country’s usage.

The chapter also briefly discusses energy storage. Gates mentions that improving on lithium-iron batteries is proving more difficult than expected - he thinks that they can be improved by a factor of 3, but not 50. He’s also lost money on battery-related startups.

Another way of storing energy is pumped hydro, where water is pumped into a reservoir, and later release to produce electricity at desired time. The top 10 hydro facilities in the USA store less than one hour’s worh of country’s electricity needs at the moment.

Thermal storage offers another alternative. It relies on materials that can keep the heat without losing too much of it over time, like molten salts. It can offer 50-60% efficiency, which is not too bad.

Hydrogen can also be used to store energy that can be turned into electricity at the desired time. Storing hydrogen has its own issues (needs to be pressured for space efficiency, hydrogen slowly leaks through metal containers), but if we used clean electricity to produce hydrogen (electrolysis), and we decreased the cost of doing so, it could provide a valuable form of storage.

The chapter discusses capturing carbon. Point capture focuses on where the CO2 is produced (e.g. at the existing fossil fuel plants). An advantage of that approach is the high concentration of CO2 in the air(often around 10%). Direct carbon capture (DAC) focuses instead on capturing carbon from the air anywhere in the world, but it’s made more challenging by the fact that on average only 1 in 2,500 molecules in the atmosphere are actually CO2.

As a final note, Gates discusses how his own opinion on using less has shifted to more favourable, once he realised just how much land would be required to meet the raising electricity demands with solar and wind power alone.

Tags: electricity intermittency transmission fission fusion nuclear power ITER geothermal pumped hydro thermal storage hydrogen electrolysis carbon capture DAC

Chapter: How we make things
  • materials like steel, concrete, glass & plastics are important to modern lifestyles
  • producing them releases CO2 into the atmosphere
  • some materials, like concrete, are harder to turn carbon-neutral than others
  • electrification relying on clean electricity production can help

When you look at various signs of improving lifestyles, you see a lot of man-made materials. Skyscrapers are full of concrete, steel & glass. Cars & electronics contain plenty of plastics. These materials are extremely successful, but the way we produce them at the moment releases a lot of greenhouse gases into the atmosphere.

Steel is made of iron and carbon, and is both strong and easy to bend while hot. The form of iron that you dig out of the ground (iron ore) is polluted with other elements. To make steel, you melt the iron ore at high temperature in the presence of oxygen & carbon. The byproduct is CO2 - 1.8 tons of CO2 for every 1 ton of steel produced. The world is expected to produce about 5 billion tons of CO2 yearly from steel production by 2050.

Concrete production offers a similar story. To make concrete, you use cement. To make cement, you use calcium. To get calcium, you burn limestone, and produce 1 ton of CO2 for every ton of calcium. This contributes another 4 billion tons per year at the moment, and currently there is no known way to produce cement without releasing CO2.

Plastics, specifically synthetic plastics, are made of carbon mixed with other elements like hydrogen and oxygen. The carbon is typically taken from a fossil fuel, and while the good news is that instead of going into the atmosphere, a large proportion of the carbon ends up in the end material; the bad news is that the carbon bonds are very durable, and the plastics we produce can take hundreds of years to degrade, ending up with all kinds of problems from poisoning marine life, to filling up landfills for centuries.

To address the emissions linked to these materials, you need to look at all the stages involved:

  • electricity needed to run the factories & equipment
  • the way to generate the heat needed
  • the side products of actually making the materials in question

The first problem is the one of clean electricity, discusses in previous chapter. The second one requires high temperatures that typically require either burning a fossil fuel or nuclear energy. Capturing back some of the CO2 produced can help. The third problem is the hardest, and we don’t have a solution in some cases. We can offset some of that with more carbon capture.

Added all together, the green premiums (extra cost to make the process greenhouse gas-netural) end up being 75-140% for cement, 16-29% for steel and 9-15% for plastics.

How can we get these to be lower? Use clean electricity, and electrify the existing process as much as possible. For example, a new process called molten oxide electrolysis can purify the iron needed for steel production without requiring high temperatures currently achieved through burning fossil fuels.

And given that plastics contain a lot of carbon, they have the hypthetical potential to become carbon sinks - if we could capture it from other processes.

Tags: steel concrete cement glass plastics molten oxide electrolysis DAC

Chapter: How we grow things
  • agriculture produces greenhouse gases through enteric fermentation, manure & fertilizer use and production
  • as much as 40% of all food in the USA is wasted
  • deforestation contributes about 30% of emissions in this category, but we don’t have enough landmass to offset our emissions just through planting more trees

19% of the 51 billion tons of CO2e falls under the category called “agriculture, forestry and other land uses”. With agriculture, the primary greenhouse gases are methane (causes 28 times more warming per molecule than CO2), and nitrous oxide (causes 265 times more warming).

Thanks to various breakthroughs, like Norman Borlaug’s modified semi-dwarf wheat which yields more than plain old wheat, the prices of food tend to get lower over time, not higher. And as people get richer, they tend to eat more meat, which contributes to increased emissions. To raise a chicken, we need to provide two calories’ worth of food for each calorie of the end product. It’s three and six, respectively, for pigs and beef. So the problem is this: how to produce more food, bigger percentage of which will be meat, without increasing the greenhouse emissions.

There is about a billion cattle raised for beef and diary around the world. When cattle eats grass, they leverage bacteria in their stomachs (in a process called enteric fermentation) to digest it. The side product burped by these cows is primarily methane, which accounts for about 2 billion CO2e, or 4% of all global emissions. Additionally, animal poop, while it decomposes, it produces various greenhouse gasses; primarily nitrous oxide and methane, sulfur and ammonia. The manure is the second biggest cause of emissions in this category.

The attemps to reduce animal breeding-related emissions have been largely unsuccessful. Short of stopping to breed livestock, attempts have been made to produce plant-based meat substitutes (Gates mentions Beyond Meat, and Impossible Foods, two companies he’s invested in), or lab-grown meat, where real animal tissue is extracted from a life animal, and then grown in the lab (currently very expensively).

Food waste itself is believed to contribute around 3.3 billion tons of CO2e each year. In Europe, parts of Asia and Africa, about 20% of food is wasted. In the USA, about 40% of all foods ends up in the bin.

Synthetic fertilizer was a key factor in the agricultural revolution in the 1960 and 70ties, that nearly quadrupled the yields of farmers in the USA. Plants’ growth is in big part driven by the presence of nitrogen. Most plants can’t produce it, and they rely on microbes in the soil to turn ammonia into nitrogen. That’s why, for epochs, humans used natural fertilizers like manure to increase crop yields.

The breakthrough, Haber-Bosch process, came in 1908, and allows us to create ammonia from nitrogen and hydrogen in the factory. However, using an artificial fertilizer has it’s downsides. For one, it disrupts the natural organisms in the soil, and they stop producing nitrogen. In addition, the extra fertilizer ends up evaporating in the form of nitrous oxide and polluting surface waters.

In 2010, the making of fertilizer (which includes high temperatures) contributed about 1.3 billion tons of CO2e, and at the moment, we don’t have a practical way of making it a zero-carbon way.

Some of the ideas explored include modified plants that can get bacteria to produce nitrogen for them, or modified bacteria that always produces nitrogen, even if it’s already present in the soil.

The remaining 30% of the emissions are largely due to the deforestation. The deforestation happens in different places for different reasons, including making room for breeding livestock, or planting lucrative plants to produce things like palm oil. While we certainly need to slow down the deforestation, just planting trees doesn’t solve the problem either. As a rule of thumb, an average tree will capture about 4 tons of carbon over its 40 year lifespan. That means, that just to cover the current emissions of the USA, we would need to plant 16 billion acres of trees, or roughly half the landmass of the world. The author’s recommendation is thus to focus on stopping cutting down trees.

Tags: norman borlaug semi-dwarf wheat enteric fermentation manure plant-based meat Beyond Meat Impossible Foods lab-grown meat food waste nitrogen fertilizer nitrous oxide Haber-Bosch planting trees

Chapter: How we get around
  • gasoline is energy dense and cheap, which makes it hard to replace
  • we should electrify the vehicles we can, and use altenative fuels for the rest

Gasoline is simultaneusly remarkably energy dense and cheap. A gallon of gas contains the same amount of energy as 130 sticks of dynamine, and it’s cheaper than milk or orange juice. Which makes it hard to replace - we’ll need something that’s just as energy dense and jusrt as cheap.

Transportation is usually the first thing people think about when asked about emissions. Globally, it’s 16% of global emissions. In the USA, however, it’s the number 1 cause for emissions.

The emissions in this category break into several sub-categories:

  • 47% - passenger cars, SUVs and motorcycles
  • 30% - garbage tracks, buses and 18-wheelers
  • 10% - cargo and cruise ships
  • 10% - airplanes
  • 3% - others

The passenger cars are the biggest category, with over 1 billion cars on the road around the world. The best way to clean up this lot is to choose electric vehicles (the author predicts green premiums to reach zero by 2030) and make sure that the electricty used to power it is carbon-neutral. When considering electric vehicles, it’s not just the price of gas and electricity that matters, as EVs tend to cost less in maintenance. Currently, less than 2% of all new vehicles sold are EVs globally.

Another option is to use liquid fuels that reuse the carbon already present in the atmosphere. “Alternative fuels” is often used to describe ethanol. Ethanol is already widely used - most gasoline in the USA contains about 10% ethanol. However, depending on how it’s produced, it might not be low-carbon, and the land it uses competes with other crops.

Second generation biofuels, including using switchgrass, try to address these issues, and sometimes offer a drop-in replacements to gasoline. However, at the moment, their price commands over 100% green premium.

Another alternative, called electrofuels, used electricity to combine the hydrogen in water with carbon in carbon dioxide, resulting in hydrocarbon fuels. While they provide a carbon-neutral option, they’re currently very expensive, at 237% premium, and it’s benefits rely on using carbon-neutral electricity.

Garbage tracks, buses and 18-wheelers can be split into two categories: medium-duty, where electrifying makes sense; and heavy-duty, where the size and weight of the batteries required stops making sense. Pound for pound, the best lithium-ion batteries on the market are 35 times heavier than gasoline that contains the same energy. Co an electric bus driving around a city is easier to make sense than a heavy lorry driving across the country. Advanced biofuels and electrofuels are both available at similar green premiums to passenger cars (103% and 234%, respectively).

Ships and planes take the same problem to the extreme. In addition, container ships use bunker fuel, which is even cheaper than regular gasoline, so the green premiums for advanced biofuels and electrofuels become even higher (326% and 601%, respectively.) While batteries keep improving, it’s hard to see how they can compete with jet fuel on price. The advanced biofuels and electrofuels are available, at 141% and 296% premiums.

What else can we do? We could travel less, and we can get more efficient using fuels. We could also use nuclear energy for large container ships, using the technology powering military ships.

The prescription for solving the transportation problem becomes rather clean-cut: electrify all the vehicles we can, and try to bring down the price of lower-emission fuels for the rest.

Tags: gasoline electric vehicle EV gasoline advanced biofuel electrofuel container ship tracks SUV

Chapter: How we keep cool and stay warm
  • 90% of American households have AC, and it’s the single biggest electricty consumer
  • existing technology can already improve AC power demand significantly
  • technologies like heat pumps are already more efficient & cheaper than fossil-fuel powered options
  • to electrify heating, we need carbon-neutral electricity

The first machine to cool the air is credited to John Gorrie, a physician in Florida, who tried to help his patients recover from malaria. Built in the 1840, it relied on a block of ice to cool the room. In 1902 Willis Carrier, an engineer working in a print shop, designed a machine to decrease humidity in a room while also decreasing the temperature, and started the air-conditioning industry.

Today, 90% of American households have some kind of air conditioning, and it’s the household’s largest electricity consumer. Worldwide, there is an estimated 1.6 billion units, unevenly distributed primarily in rich countries. The number is expected to hit 5 billion by 2050, tripling the energy demand.

As it turns out, we can make a big difference by just using more efficient, more modern units. Some estimates place an average unit to be only half as efficient as the the best models available now. Regulations, including clean way of marking efficiency and long-term costs of units, can help with that.

The greenhouse emissions are also due to the refrigerants - known as F-gases - which slowly escape aging AC units, and have a powerful effect of warming up the atmosphere.

The other side of the equation is heating - our offices, homes & water furnaces. The approach is similar the personal cars: electrify what you can, and find cheap alternative fuels for the rest.

One of the existing technologies is a heat pump. It leverages the fact that gases and liquids change their temperature as they expand and contract. This allows heat pumps to move heat from one place to another, just like your fridge already does. In many places, the overall cost of buying and operating a heat pump over 15 years is cheaper than using fossil fuels to heat and cool the building. So why aren’t they more widely used?partly, due to the long lifespan of installations, and partly due to outdated policies favouring things like natural gas over an electric alternative, which is less efficient.

Yet again, the suggested solution relies on decarbonising the power grid - none of this helps, if the electricity is not produced in a carbon-neutral way.

The chapter also mentions Seattle’s Bullitt Centre, which at times can produce 60% more energy than it needs to run. Even though that building is very expensive, some of the technologies have a good chance of spreading around; for example, supertight envelope (little air gets in and out), triple glazing, good insulation, efficient doors, and smart windows, which automatically tint to keep the room cool, and turn lighter to let it warm up.

Tags: AC John Gorrie Willis Carrier F-gases refrigerants heat pump fridge Bullitt Center supertight envelope triple glazing smart windows

Chapter: Adapting to a warmer world
  • just about everyone who’s alive today will need to adapt to the warmer world
  • all cities will be affected, but the coastal ones will be affected more
  • we should invest in our natural defences
  • there is an economical case, not only moral, to deploying new funds to prevent climate change
  • geoengineering, or engineering a change in the atmosphere to cool down the planet, might be a break-glass solution that we need

Gates asserts, that just about everyone alive today will need to adapt to a warmer world, but the its effects won’t be distributed evenly. Even though people in the poorer parts of the world do the least to cause emissions, they are the most likely to suffer from it. For example, what will be a problem to deal with for a comparatively well-off farmer in North America might completely wipe out a substanance farmer in Africa or Asia. Increased draughts and floods are likley to drive the food prices up, and that will be felt the most by the poorest, millions of whom are already spending more than half of their incomes on food. And food insecurity will contribute to the raise in rates of malnurishment, and declining health care overall. Therefore any philantropic efforts should prioritise health care and preventing malnourishment.

CGIAR (Consultative Group for International Agricultural Research) helps create better palnts and better animal genetics. Norman Borlaug’s wheat breathrough happened at their labs, and so did the invention of “scuba” rice, which can survive being submerged in water for up to two weeks, making it much better at surviving floods. Another example is a deployment of modified maize seed in Zimbabwe, which allowed for 600 kg higher yields per hectare, thanks to its drought-tolerant properties. CGIAR also works on other technologies, including an app to diagnose cassava pests and diseases using a smartphone.

Gates makes three recommendation related to the agriculture: help farmers manage the risks from more chaotic weather; focus on the most vulnerable people; factors climate change into policy decisions.

For cities specifically, the author offers a three-stage plan. First, reduce the risks posed by warming planet. Second, prepare for emergencies. And third, plan for the recovery period after disasters.

All cities will be affected, but the coastal ones will be affected the most. The city planners should gather the data on climate risks and projections from computer models to make informed decisions on how to grow their cities, and where to invest first to protect them from storms and raising sea levels, for example. And cities with a lot of hot days will need to invest in cooling centers, where people can flee the heat.

We should also invest in our natural defences. For example, forests store and regulate water, wetlands prevent floods and coral reefs provide home to the fish that coastal towns rely on for food. A good example is that of mangroves. They are short trees that grow along coastlines, adopted to saltwater, and help reduce storm surges. The mangroves alone can save the world about $80 billion a year in losses to floods.

We will also need to produce more drinking water. As freshwater sources dry up, we will need to innovate to continue providing potable water to populations. The desalination technology already exists, but it’s very energy-heavy, so it boils back to the question of generating clean electricity.

It’s clear, that we’re going to need to unlock more money to fund these projects. Gates estimated that an investment of $1.8 trillion into five key areas (early warning systems, waste management, climate-resiliant infrastructure, raising crop yields, and protecting mangroves) would yield more than $7 trillion between 2020 and 2030. So the case is not just morally justified, but also economically.

If all that fails, we might be left with no other option than to try to engineer an emergency solution to cool down the planet. Various approaches all under the common umbrella of “geoengineering”, and they all rely on putting things in the atmosphere to reflect some of the energy back, for example spraying salts. This has the advantage of being comparatively simple & cheap, but it’s often criticised as conducting a planet-scale expriment. But we’re already conducing one - by putting more greenhouse gases in the atmosphere - so we might need a break-glass solution. Gates is advising to at least discuss and research, so that we can be more prepared if such a need arises more suddenly than we expect.

Tags: CGIAR cities mangrove geoengineering