Random tools

Climate engineers already have a range of tools which are fully capable of satisfying consumer demand for climate stability.

We should not assume that all potential climate engineering tools have been invented. As in every field of engineering, there is plenty of room for further innovation. However, we have enough tools to get started.

Atmospheric Content Modulation

We can be highly confident that controlling the content of the earth’s atmosphere will control global surface temperatures. Adding more greenhouse gases warms the climate: Removing greenhouse gases cools it down.

Not all greenhouse gases are equal. Adding carbon dioxide warms the climate for many thousands of years; Releasing methane into the atmosphere affects temperatures for only a few decades.

Climate diplomats and politicians generally support Atmospheric Content Modulation for managing global temperature. The 2015 Paris Climate Accord calls for “net-zero” human-made greenhouse gas emissions. Human-made emissions of each gas must be cancelled out by human-made removals.

There are dozens of greenhouse gases. But although climate engineers could use any greenhouse gas to warm or cool the earth’s climate, most planning and discussion is focussed on carbon dioxide (CO2).

As a climate engineering tool, CO2 has the important advantage that it acts very slowly. Annual net CO2 emissions are humongous. Counting all the oil, coal, natural gas, and other sources, human-made CO2 emissions in 2022 totalled about 42 billion tonnes. At that rate, it would take about 44 years to increase average surface temperature by 1 °C. In other words, it takes a LOT of CO2 to change global temperature or sea level. This helps engineers manage risk, because they will have plenty of time to make sure they are not overdoing CO2 removal or addition. Also, using a slow-acting tool like CO2 ensures the whole atmosphere is evenly mixed.

CO2 is non-toxic at the concentrations likely to be used for climate engineering. Within reason, engineers can add or subtract pretty-much any amount of CO2 to the atmosphere. The technology for harvesting CO2 from the atmosphere has already been well proven on submarines and spacecraft. The earth has plenty of places to store harvested CO2. If engineers need to warm the climate, they can easily boost CO2 by burning fossil fuels (more than 85% of the world’s fossil energy resources are still in the ground) or by converting a forest to grassland.

Solar Radiation Modulation

The earth’s greenhouse effect works by trapping heat from the sun. In theory, climate engineers could adjust global surface temperature by controlling the amount of solar heat arriving at the earth, or by controlling the amount of heat radiated from the earth out into space.
The most straightforward proposal is to build a sunshade between the earth and the sun. Wikipedia covers several solar sunshade designs. The usual approach is to locate the sunshade at the L-1 point, where the earth and sun’s gravity cancel out. A solar sunshade would give very precise control of the amount of solar energy reaching the earth. However, it might prove to be more expensive than other climate engineering tools.

Another well-researched concept is to sprinkle fine particles in the upper stratosphere, where they would reflect some of the sun’s heat back out into space. At a very high altitude, a tiny amount of material could reduce global temperature enough to achieve temperature stability. The particles would gradually waft down to lower altitudes. A small fleet of high altitude balloons or robotic aircraft would need to keep adding new material to the upper stratosphere. There are many different materials that could be used. Systems that have been modelled would not cause significant air pollution at ground level.

Other possible methods of managing solar heat include painting roofs and other structures white to reflect sunlight back into space, and boosting reflection from clouds by spraying material into the lower atmosphere (troposphere), usually over the open ocean.

Future Tools

Expect to hear about new climate engineering tools from time to time. A new field like Climate Engineering has plenty of scope for innovation. As we learn more about temperature, sea level, and other changes to climate characteristics, new information inspires fresh ideas. For example, scientists studying the effect of warming on Antarctica’s ice sheets have theorised about excavating the sea floor or dumping heaps of snow to prevent ice cliffs from falling into the sea. They worry that if those ice cliffs collapse, sea level would rise fairly quickly, and it might be very difficult to reverse (IPCC, 2021, p. 1307). Nobody knows if ice cliff stabilisation will be a real thing.

A Complementary Set of Tools

Climate Engineers already have the tools they need to satisfy consumer demand for climate stability. As with any toolkit, the right tools need to be used at the right time.

Carbon Dioxide Modulation depends on a plentiful supply of fossil carbon, for use when warming is needed. If the energy industry keeps burning fossil fuels until they’re all used up, future Climate Engineers will need to look elsewhere for something to stave off some future ice age.

Right now, Climate Engineers are expected to cool the climate. To achieve their immediate targets, Climate Engineers need to extract most of the CO2 that’s been added in the last 170 years, and all the CO2 emitted by future fossil fuel consumption, and store it somewhere it can’t contribute to warming. Generally, this CO2 will be injected into underground reservoirs. Much of it will be permanently absorbed by rocks. If the energy industry keeps burning up fossil fuels, there is a real risk Climate Engineers would run out of places to store CO2. If, in the future, additional cooling is needed, Climate Engineers could be faced with a very difficult problem.

Solar Radiation Modulation could offset the warming caused by increased atmospheric CO2. However, this does not address ocean acidification, a side effect of increasing CO2 that worries conservationists and could damage fisheries.

Climate engineering needs to start with a complete phase out of fossil fuel consumption. This would be followed by an atmospheric CO2 reduction programme, aiming to bring atmospheric CO2 back to somewhere near its “pre-industrial” concentration. I appreciate that this seems radical. That’s why I put together a hypothetical scenario showing how CO2-neutral hydrocarbon fuels (gasoline, diesel, jet fuel, and BBQ fuel) can be made with solar energy and CO2 extracted directly from the atmosphere. Solar hydrocarbons would totally replace conventional fuels during a 60-year phase-out of fossil fuel sales. Under that scenario, the affordability of gasoline gradually improves as time goes on. No-one would be forced to buy a battery or hydrogen powered car. The next step in that scenario would be to make hydrocarbon fuels “CO2-negative”. We have the technology to do this right now.

Once the fossil fuel phase-out gets underway, Climate Engineers will be able to think about the role of Solar Radiation Modulation (SRM). If there is a risk that Atmospheric Content Modulation will take too long to achieve an important outcome, such as preventing rapid sea level rise, SRM could be used to temporarily reduce warming.

Climate Engineering is a new branch of Habitat Engineering. It is starting out with a well-stocked toolbox which is more than capable of satisfying consumer demand for sea level stability.

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