Global strategies

Marine cloud-brightening is a technique that could increase the albedo of marine stratocumulus clouds and thus help mitigate global warming. One of the articles linked here (1) explains how wind-driven spray ships are used to release micrometer-sized droplets of seawater into the boundary layer beneath marine stratocumulus clouds, increasing their ability to reflect solar energy. The technique takes advantage of the Twomey effect which states, that multiple smaller droplets provide a better ability to reflect solar radiation than a smaller number of larger droplets. The spray vessels used for this purpose can be powered by carbon-neutral Flettner rotors, which double as convenient housings for the spray nozzles. The article estimates that to cancel out the thermal effects of a one-year increase in global CO₂ levels, it would only take the equivalent of about 64-127 million dollars to build the technologies used to do so. This article provides information on the wind-driven spray ships, powered by Flettner rotors, used for this purpose.

This comparatively inexpensive method of curbing global warming also carries some risks, if applied uncritical, immediate and at the maximum, that cannot be seriously predicted. Another article linked here (2) includes studies showing that MCB can potentially cause changes in temperature and precipitation that can be both positive and negative depending on the region.

This is why you should explore such such efforts first only on a really small scale (e.g. grid of 3 x 3 ships each separated by 10 km) for some years so that everything is still fully reversible - this is called a climate mitigation strategy. It is essential to see the difference between geoengineering and climate mitigation strategies: Irreversible geoengineering is rather risky, careful exploring all options to mitigate climate in a reversible way (soon after exploration is stopped, all small climate effects fade off, too) is essential to find a bundle of different options for safe action in ten years, when global warming becomes ever more detrimental.

We are advocating to test a number of different climate protection strategies, so that we have a choice and can find the safest but also most climate preserving cocktail of countermeasures. Because the riskiest strategy in the fight against global warming is to do nothing at all due to possible negative effects and leave promising climate mitigation strategies such as MCB unexplored and untested.

Another article linked here provides information on possible field experiments that could help to better assess the impact of the MCB on climate. (3)

The combustion of crude oil-based fuels, such as kerosene, releases CO2, nitrogen oxides and other particulates directly into the Earth's lower atmospheric layers, the troposphere. (1) Although aviation only accounts for about three to five percent of total emissions of harmful greenhouse gases, the sector is experiencing strong annual growth, making the development of climate-friendly kerosene increasingly interesting from a climate protection perspective. (1)

One important approach to this is so-called power-to-liquid (PtL), i.e. the use of solar and wind energy to produce fuels from water and CO2. (2) Even though the cost of producing PtL can be expected to fall steadily, the production costs will still be significantly higher than the prices of the fossil fuels currently used. (3) A major challenge, is to reduce the cost of capturing CO2 from the air through what is known as "direct air capture" (DAC). In a publication on the prospects of DAC, half of the experts surveyed cited the lack of supportive policies as the main obstacle to the development of DAC projects. (4) Even among the best prospects for developing DAC technology, it can be said that its direct use, or for the production of PtL fuels, can only be considered as part of a comprehensive portfolio of climate mitigation strategies and cannot alone ensure that climate targets are met by 2050. (4) 

Another approach to producing more climate-friendly fuels is so-called biomass-to-liquid (BtL), i.e., the conversion of biological feedstocks into synthesis gases. (5) Suitable for this are, for example, certain plants grown for this purpose, but also forestry waste, various residual materials, algae or animal fats. Challenges of the method are, on the one hand, the limited arable land required for biomass production, as the population is constantly growing and more and more land is needed for food production. This is a problem that would not arise with the PtL method, since the renewable energy farms needed for production function more effectively in desert-like regions anyway, where biomass cultivation is not possible. Another advantage of the PtL method, is the much lower water requirement, compared to various BtL methods. (6) 

In summary, neither method offers an ultimate solution for the production of sustainable kerosene that can soon be used on a large scale. According to a study on BtL and PtL conducted for the German Federal Ministry of Transport and Digital Infrastructure (BMVI), the medium- and long-term volume demand for renewable kerosene can only be met if fuels developed on the basis of both methods are used. (7) 

In order to promote the use of sustainable kerosene, a binding and appropriate pricing of CO2 emissions is of crucial importance. (8) This would lower the price of climate-friendly fuels relative to conventional fuels. As mentioned above, government support for the whole thing is a crucial factor. But also in the private one can make an important contribution to the conversion to climaticfriendly fuels, by booking for example its airline tickets only with airlines, which support the development and the use of lasting, kerosene. To do this, simply find out briefly on the Internet about the current situation and then select the airline that is the most suitable according to your own research. 
 

The permafrost soils in the high latitudes are permanently frozen reservoirs of a large amount of organic material, which has been protected from microbial decomposition for thousands of years. When this storage layer thaws, the microorganisms it contains become active and the decomposition of the organic material releases greenhouse gases such as CO₂ and methane (CH₄). Most estimates of the amount of organic carbon contained in permafrost soils are around 1400-1600 gigatonnes (Gt). (1,2,3) Even though methane is produced in far smaller quantities in thawing permafrost than CO₂, it must be considered that it is by comparison a far more effective greenhouse gas.

As things stand today, there are two conceivable approaches to cooling the permafrost and thus protecting it from thawing. In summer, one can protect the frozen ground by covering it with a layer that reflects the sunbeams before they can hit the ground and heat it up. In total contrast, in winter one can free the ground from the heat-insulating snow cover so that it can be cooled by the low air temperatures.

Since 1993 there has been a project by the "Bayerische Zugspitzbahn", which spreads a reflective plastic sheet over the northern "Schneeferner" in the summer months. (4) This elaborate measure was put into practice annually until 2012. A year later, however, the project was abandoned as it was declared too inefficient in the face of rapidly advancing climate change. (5) A promising method that could be used on a much larger scale is marine cloud brightening. The Centre for Climate Repair (CCR) at Cambridge University is devoting a large part of its research to this idea. (6)

Under the slogan "Refreeze the Arctic", the CCR is pursuing yet another strategy aimed at protecting the frozen layer of ice on the water. Their website explains that thick layers of ice on the water are better at insulating cold than thin layers. It is therefore being investigated whether it is possible to pump seawater onto previously formed ice floes in order to effectively increase their thickness. (6)

To expose the permafrost to the cooling ambient air in winter, one conceivable approach is to reintroduce a large number of different massive herbivores to the high latitudes. These dig up the snow cover in winter to access the food material underneath. By restoring a large animal fauna similar to the Pleistocene, the "Pleistocene Park" project, besides the direct cooling effect on the soil, also holds out the prospect of increasing the rate of photosynthesis through the regeneration of a highly productive steppe tundra with the help of special seeds. Other positive effects mentioned are the increased reflection of the sun in these areas, as pastures have a higher albedo effect than barren land. In general, the project aims at both climate protection and the resurgence of biodiversity in the high latitudes. (7)

Power-to-x refers to processes in which electricity is converted into other substances. Of course, these processes only have something to do with sustainability if renewable energy is used as the power source. If this condition is met, various power-to-x processes have the potential to become important climate mitigation strategies.

Power-to-chemicals

This term covers all processes in which electricity is used in the production of chemicals. For example, the "P2X" project [LINK] of the German Federal Ministry of Education and Research is investigating how hydrogen can be converted together with CO2 into polymer building blocks, which the chemical industry urgently needs. (1) This industry consumes an enormous amount of energy in the production of several million tonnes of chemicals and is estimated to cause "one seventh of anthropogenic greenhouse gas emissions". (2)

Power-to-fuel

This term describes all processes in which fuel is produced with the help of electricity. If only renewable energy is used, the production of climate-neutral fuels is possible. For more information on this topic, read the article on "Green paraffin" a little further up this page.

Power-to-gas

This term is used to describe all processes that use electricity to produce gases such as hydrogen. Although hydrogen is one of the most abundant elements in the universe, it cannot simply be harvested, but must be produced in a highly energy-intensive reaction called electrolysis. Since this reaction can consume more energy than the hydrogen it produces can release, hydrogen is not an efficient energy source with current methods of extraction.(3)

The following context shows why the production of hydrogen nevertheless represents a possible climate mitigation strategy.

A central challenge in the transition to renewable energy sources is the storage problem. Although there are many technical concepts, none has yet proven to be efficient in large-scale deployment.(4) Already today, electricity from solar panels and wind turbines can be stored mainly in pumped storage power plants, which are very efficient, but possible locations are limited.(5) Hydrogen as energy storage could be a good solution, as the energy it contains can be stored for a long time and is easily accessible to supply energy to a variety of processes. This development is currently hampered by the limited availability of renewable energy and also by concerns about general safety, as hydrogen is a highly flammable gas. Once these hurdles are overcome, however, hydrogen as an energy storage medium could pave the way for the global shift to renewable energy.