Geoengineering

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The collective term geoengineering (also geoengineering or climate engineering ) describes intentional and large-scale interventions with technical means in geochemical or biogeochemical cycles of the earth. The main goals of such interventions are curbing anthropogenic global warming , for example by reducing the CO 2 concentration in the atmosphere , or reducing the acidification of the seas .

A distinction is made between projects on Solar Radiation Management (SRM), which are intended to reduce incident solar radiation , and Carbon Dioxide Removal (CDR), which remove greenhouse gases such as carbon dioxide (CO 2 ) from the atmosphere and store them as permanently as possible. What all projects have in common is the shift in costs into the future.

Many proposed geoengineering technologies are not available on a planetary scale and their technical feasibility, environmental, financial, social and political costs and risks are unknown. The possible contributions of geoengineering are therefore also assessed in climate models .

history

Attempts to modify the regional weather have been around for centuries, and around 50 countries are still pursuing such approaches today. The first recommendation for researching the possibilities and effects of compensating for global man-made warming by increasing the reflectivity ( albedo ) of the earth dates back to 1965. In that research report called Restoring the Quality of Our Environment , which was prepared for the President of the USA However, the term "geoengineering" was not yet used.

The term geoengineering was coined in the 1970s by the Italian physicist Cesare Marchetti . Marchetti linked him with his proposal for CO 2 capture and storage (CCS): In order to counter the risk of global warming, CO 2 should be captured in coal-fired power stations and oil refineries and fed into permanent storage. He gave preference to deep-sea transport using ocean currents over the limited capacity of exhausted natural gas fields .

Initially used only in scientific circles, the term became popular with the publication of a study by the National Academy of Sciences on the possible effects of global warming in 1992. By the year 2000 research had progressed so far that a first review was published. The first publications on simulation models also appeared around the turn of the millennium.

With an influential publication by Nobel Prize winner Paul Crutzen in 2006 on the injection of sulfur into the stratosphere, geoengineering moved further into the public eye. More scientists began to study geoengineering proposals. Social, political, ethical and legal implications moved into the focus of social scientists, philosophers, economists, political and legal experts.

While these purely technical approaches were not taken seriously in political and scientific circles until the mid-2000s, since then, in the course of the ongoing discussion about global warming, such strategies have not only been proposed more often by scientists, but are also being seriously considered by individual governments. The first tests have been carried out ( EisenEx and LOHAFEX experiments ) and others are being planned or postponed due to public pressure (SPICE experiment).

The member states of the United Nations Framework Convention on Climate Change agreed in 1992 to avoid dangerous disruption of the climate. Following on from this, in 2015, in the Paris Agreement , they set themselves the goal of limiting global warming to well below 2 ° C and , if possible, below 1.5 ° C , and for this purpose to submit national contributions to the necessary emission reductions. In view of the incompatibility of the actual and planned emission reductions with the climate targets, the focus shifted to the extent to which additional geoengineering measures, in particular negative emissions through carbon dioxide removal , can and must contribute to their compliance. In its special report on the 1.5 ° C target in 2018, the Intergovernmental Panel on Climate Change came to the conclusion that in most future paths that are in line with the targets, greenhouse gases must be removed from the earth's atmosphere to a considerable extent. However, the proposed technologies cannot be used on a large scale for a long time, there is a lack of legal and political framework conditions and there is considerable uncertainty about negative side effects. Although some of the proposals could ultimately achieve the potential to limit global warming in a purely physical manner, they cannot reliably contribute to meeting the climate targets.

Concept and classification

definition

In its fifth assessment report, the Intergovernmental Panel on Climate Change defines geoengineering as "a broad group of methods and technologies that aim to intentionally change the climate system in order to mitigate the consequences of climate change ." ( IPCC : Climate Change 2013: The Physical Science Basis. Annex III : Glossary). In its similar definition, the Royal Society describes geoengineering as "the deliberate large-scale intervention in the Earth's climate system in order to slow down global warming."

Willfulness and large scale are usually seen as essential to the definition. When coal and oil are burned in power plants and engines, in addition to CO 2 , sulphate aerosols are also produced , which have a cooling effect on the climate. However, because the climate impact is unintentional, it does not count as geoengineering. The goal of large-scale and long-term climate changes distinguishes geoengineering from the rather small-scale, short-lived weather modification .

The word engineering can give the misleading impression that geoengineering is about the technical control of the entire climate system. With large-scale interventions in elements of the radiation balance and the earth's carbon cycle , far-reaching side effects are difficult to predict and hardly avoidable.

Counter-geoengineering is one way that states could react to unilateral geoengineering in the event of a conflict. The term refers to geoengineering measures for global warming, which are intended to counteract cooling measures, for example the additional emission of very effective greenhouse gases such as chlorofluorocarbons .

Main groups

The term "geoengineering" encompasses very different considerations. Because of their different approaches, these proposals are divided into two main groups:

Influencing solar radiation (radiation management, English Solar Radiation Management, SRM)
Proposed techniques for the reduction of sunlight ( Solar Radiation Management (SRM) )
These techniques aim to increase the reflection of the incident short-wave sunlight. They thus counteract the global rise in temperature. The actual cause of this impending rise in temperature, the concentration of greenhouse gases in the atmosphere and their other effects, such as the acidification of the oceans , cannot be directly influenced with SRM; a previous climatic condition cannot be restored with it.
It is assumed that these methods would bring a cooling effect relatively quickly in the event of an impending climate catastrophe. However, aerosol application methods in particular involve great risks with regard to undesirable side effects (such as damage to the ozone layer or negative effects on human, animal and plant health).
Reduction of the CO 2 concentration in the atmosphere (Carbon Dioxide Removal, CDR)
Carbon Dioxide Removal aims to release more CO 2 from the atmosphere into carbon sinks such as the oceans, the biosphere or the soil ( pedosphere ) (negative emissions). It includes direct CO 2 influencing methods such as air filtering, CO 2 capture and storage (CCS) , but also indirect methods intended to increase the absorption capacity of carbon sinks, such as fertilizing the oceans with iron or phosphorus.
Since these methods address the main cause of global warming , the increasing CO 2 concentrations, their uncertainties and side effects are estimated to be lower compared to radiation management. However, there are still considerable uncertainties, for example due to feedback with carbon sinks and with other biogeochemical cycles such as the water cycle and the earth's surface albedo . CDR methods take many decades to achieve significant reductions in greenhouse gas concentrations. In contrast to SRM methods, they are only effective in the long term. The effect on the world's oceans is much more sluggish. If the CO 2 emissions continue to rise as before, the resulting acidification of the seas, through which numerous marine species are threatened with extinction, will continue for centuries even with CDR.

There are also other measures that cannot be clearly assigned to either of the two groups. High cirrus clouds have a warming effect on the climate. The introduction of certain ice crystals as cloud condensation nuclei by airplanes could change their properties in such a way that more of the long-wave heat radiation leaves the atmosphere through them. In this respect, the measure is similar to Carbon Dioxide Removal, because if the CO 2 concentration is reduced , more long-wave thermal radiation can also escape. On the other hand, it has characteristics of the SRM, for example this measure also threatens a termination effect , i. H. an abrupt warming when interrupted. In order to group this important proposal under radiation management , one sometimes speaks of Radiation Management (RM) instead of Solar Radiation Management (SRM).

Occasionally, technical measures are also discussed to prevent the greenhouse gas methane from entering the atmosphere from natural reservoirs or to remove it from the atmosphere again ( methane removal ).

important characteristics

Proposed geoengineering techniques can include: a. distinguish

  • according to the scale and intensity of their necessary use or their effect
  • according to whether they have an impact across borders or on global commodities (the latter include the global water balance, the world's oceans, the Antarctic or the atmosphere)
  • according to the speed with which they take effect and the longevity of their effect.

Whether a geoengineering technique is only effective regionally or across borders is decisive for its political and international legal evaluation .

In general, radiation management measures are effective much faster than CDR measures, but are also less permanent. If they are interrupted, the so-called termination effect or termination shock threatens : rapid climate changes that would be many times faster than the current - according to geological standards - already very rapid climate change.

Differentiation from climate protection and adaptation

The boundaries between geoengineering, climate protection and adaptation are blurred. The Intergovernmental Panel on Climate Change ( IPCC) subsumes the term climate protection measures that reduce greenhouse gas emissions or improve the absorption capacity of carbon sinks. This understanding includes many forms of carbon dioxide removal : CO 2 capture and storage, for example, reduce emissions, and afforestation can expand the biosphere as a carbon sink. According to the Intergovernmental Panel on Climate Change, climate adaptation includes measures that reduce the vulnerability of natural and human systems to the consequences of climate change. Measures of radiation management such as the whitening of roofs, which primarily cause small-scale climate changes such as a cooler urban climate , are therefore climate adaptation measures , but are also sometimes counted as geoengineering.

Solar Radiation Management

Radiation management methods (SRM) aim at a higher reflection of the incident solar radiation or a reduced absorption on the ground. They can be differentiated according to the location or altitude (earth's surface, troposphere, stratosphere, space) of the proposed intervention. The discussion about SRM measures focuses on the lightening of clouds and the introduction of sulfur aerosols into the stratosphere. Methods on the earth's surface are considered too ineffective, those in space are too difficult to implement technically and too expensive.

SRM does not restore the original climate condition. Here is a simulated fourfold increase in CO 2 concentrations, which is completely compensated for by the SRM. There are significant differences compared to the pre-industrial climate. Typical are relatively cooler tropics, warmer higher latitudes.

As a first approximation, SRM cools the regions into which reflected solar radiation would fall. So its effect depends on the time of day and the latitude. The warming caused by greenhouse gases is different: They are evenly distributed in the earth's atmosphere and hold back the heat reflected from the earth's surface at any time of day and at any latitude. As a result, SRM cannot restore the climate that existed before the rise in greenhouse gas concentrations. The effect on the earth's water cycle is also significantly different; precipitation would probably decrease in middle and high latitudes and increase in the tropics. In order to be able to estimate the effect of SRM, computer simulations with climate models are necessary.

SRM methods do not counteract the acidification of the oceans and the additional absorption of atmospheric CO 2 in the biosphere. Reduced solar radiation, which is the aim of most of the SRM methods, would also have an additional effect on plant growth. Proctor et al. (2018) estimated on the basis of the effects of past volcanic eruptions, the influence of the reduction and dispersion of which reaches the Earth solar radiation on the yield of corn, soybeans, rice and wheat would: An entry of sulfate aerosols according to the amount as from Pinatubo in Outbreak was released in 1991, positive effects due to reduced heat stress would be negated by the changed solar radiation. In this respect, too, SRM would not be going back to the status quo ante. The cooling effect of SRM would occur very quickly, but would also end in a short time if SRM measures were not continued. This threatens the termination effect, an abrupt climate change in a few years.

Increase in surface albedo

Basically, suggestions for increasing the reflectivity of the earth's surface consist in making it “brighter”. They find their limits in the available land surface, because the brightness of water surfaces can hardly be modified. Their effectiveness also depends heavily on how much solar radiation reaches the location of the measure, which in turn depends on the mean cloud cover and the latitude.

Suggested measures are: the whitening of roofs and settlement areas, the cultivation of lighter colored grasses and crops, no-till (the unharvested, light-colored plant material covers the darker soil) or the covering of large desert areas with reflective material. Estimates of the cost of these measures to be effective globally range in the hundreds of billions to trillions of US dollars per year.

Limited increases in surface albedo could regionally reduce warming by up to 2-3 ° C. Such “regional land radiation management” measures could be useful in particularly vulnerable areas. This could, for example, reduce temperature extremes in densely populated regions or important growing areas. The side effects would be limited in these scenarios, but simulations indicate the risk of reduced precipitation for India, China and Southeast Asia.

Elevation of the cloud albedo

There are a number of studies to increase the reflectivity of low clouds over parts of the oceans. This can be achieved with smaller and more long-lived cloud droplets. One possibility of influencing cloud formation accordingly is aircraft, ships or other watercraft specially designed for this purpose that spray seawater or sea salt in the form of fine particles into the air. Engineer Stephen Salter suggested that a fleet of wind-powered fiberglass boats with underwater turbines could produce spray water.

Stratospheric aerosols

Sulfur dioxide

A prominent approach is to transport sulfur dioxide into the stratosphere , where it oxidizes to sulfates . Water is deposited on these sulfates, so that sulfur aerosols are created, which reflect the sun's rays into space and thus weaken the warming of the earth. The idea is based on experiences with volcanic eruptions. The eruption of the Pinatubo in 1991 led to a global temperature drop of 0.5 ° C. The eruption of the Toba around 75,000 years ago led to a volcanic winter that was accompanied by an estimated 3–5 ° C cooling, according to other model calculations even 8–17 ° C. The lifespan of these aerosols in the stratosphere is about a year.

The idea originally came from the Russian climatologist Michail Budyko , who published it in the mid-1970s. The atmospheric scientist Ken Caldeira and the physicists Lowell Wood and Nathan Myhrvold from Intellectual Ventures developed the approach of pumping sulfur dioxide into the stratosphere with the help of a hose about 25 km long and a few decimeters in diameter. Helium balloons would carry the hose and several pumps attached to it. The colorless liquid gas escaping at the end of the hose would wrap around the earth within about 10 days due to stratospheric winds. The sulfur dioxide could be a waste product from oil sands mining in Canada. According to the developers, the necessary amount of sulfur corresponds to around 1% of global sulfur emissions. An idea from Intellectual Ventures based on the same physical mechanism is to extend the chimneys of several sulfur-emitting factories into the stratosphere with the help of hot air balloons and airships.

Several well-known scientists, such as the Nobel Prize in Chemistry, Paul Crutzen and the President of the NAS, Ralph J. Cicerone , advocate the similar idea of ​​raising sulfur-laden hot air balloons into the stratosphere in order to burn them there. According to Crutzen, this method would only cost US $ 25 to 50 billion annually, but has been criticized by some scientists because of possible unpredictable effects and the need for permanent sulfur transport.

The necessary amount of sulfur aerosols is difficult to determine because - if condensation nuclei are already present in the stratosphere - the sulphate could rather attach to them instead of forming new ones. Sulfur aerosols can also damage the ozone layer . In addition, this geoengineering variant would not restore the original climate, but a climate that differs regionally from it, since limiting solar radiation through sulfur particles has a very different physical effect than limiting the greenhouse effect through climate protection. Even if this method were to stop global warming on a global average, there would be regions that would warm up faster than without sulfur injections, while other regions would cool down disproportionately. So z. B. fears that the enrichment of the atmosphere with sulfur could lead to a faster warming of the southern polar sea, which in turn could accelerate the rise of the sea level through the destabilization of the West Antarctic ice sheet . Further problems are the formation of acid rain due to the release of sulfur dioxide and the fact that the acidification of the oceans would continue due to further carbon dioxide input and thus the ecosystems of the world's oceans would be further damaged. Regional climate changes such as changes in the water cycle could also not be prevented. For example, a decrease in rainfall over the continents is to be expected, which would lead to greater drying out of the land masses. As a result, there is a risk that more severe drought periods would occur with the application of sulfur in the stratosphere than without this measure.

Alumina

On September 7, 2010, David W. Keith published the proposal to apply nanoparticles consisting of aluminum , aluminum oxide and barium titanate in the stratosphere in order to reflect sunlight.

The 10 micrometer wide and 50 nanometer thick disks are supposed to float permanently at a height of 40 to 50 km, just above the stratosphere, by using the photophoretic effect. While the barium titanate side should face the earth, the aluminum / aluminum oxide side should face the sun. Most of the incident sunlight would be reflected, which increases the albedo effect and could thus help cool the earth. (The effect of photophoresis can also be observed with the light mill , the wheel of which rotates when exposed to light.)

The solar radiation heats the nanoparticles. Since barium titanate gives off heat and energy more easily than aluminum, the pressure on the underside - resulting from the photophoretic effect - would be greater than the pressure towards the earth. This excess pressure would keep the disks in a suspended state, ideally in the mesosphere . If the barium titanate layer is electrically charged, the natural electrical field of the atmosphere would keep the panes horizontal and prevent them from tilting. At night the particles would slowly sink to the earth (due to the lack of solar radiation), but would rise again during the day due to the effect described.

Keith suggested the following composition of the nanoparticles:

  • Top layer consisting of aluminum oxide (protects the middle aluminum layer)
  • Middle layer made of aluminum (reflects sunlight)
  • Lower layer made of barium titanate (for electrical charging and photophoresis)

In contrast to the sulfur dioxide models, this method of the SRM would have fewer undesirable effects on the ozone layer, since the disks would float above it. The nanoparticles would also have a longer lifespan in the stratosphere. In order to reduce negative health effects in a test phase (aluminum and barium titanate are harmful to health), the nanoparticles should ideally be manufactured in such a way that they have a limited lifespan during this period. For example, they could be made in such a way that they would be broken down by UV radiation and oxygen radicals.

Bismuth iodide

At the moment (2017) it is considered whether one can slow down global warming by introducing bismuth (III) iodide into the atmosphere. David Mitchell from the University of Nevada suggests using 160 tons annually (cost: approx. 6 million US dollars) for this.

Calcium carbonate

In 2018, Harvard University began planning the SCoPEx experiment, in which calcium carbonate particles are to be released at a height of 20 km ( stratosphere ) above the southwestern United States.

Space-based approaches

There are various proposals to position objects at the Lagrange point L1 between the earth and the sun, which orbit the earth with the earth, reduce solar radiation and thus cool the earth:

  • In 1989, James T. Early proposed the establishment of a kind of thin protective shield made of material extracted from the moon,
  • The Pentagon physicists Lowell Wood sketched space-qualified small the idea awning to install, to shade around the Earth.
  • Roger Angel from the University of Arizona came up with the idea of ​​positioning a cloud of around 20 million t (equivalent to around 15 trillion pieces) of small, transparent panes, each with a control unit for alignment.

Carbon Dioxide Removal

As far as emission reduction processes such as CO2 capture and storage or technical processes such as direct air carbon capture and storage are concerned, this is not yet associated with geoengineering in the narrower sense, as no planetary, biological or geochemical processes are changed.

Carbon Dioxide Removal (CDR), also known as carbon dioxide removal, is the targeted removal of CO 2 from the atmosphere and its storage in other carbon reservoirs. A flow of atmospheric carbon into permanent carbon sinks caused by CDR is also referred to as negative emissions , the corresponding CDR technologies are also known as negative emissions technologies (NET). 82% of all scenarios in the special report 1.5 ° C global warming to meet the two-degree target require negative emissions and thus the large-scale use of CDR. Without CDR, you will likely not be able to stay below the 1.5 degree limit . In these scenarios, CDR use will start in the median from 2021 and will reach 14.1 Gt CO 2 / year in 2050.

There are proposals for biological, chemical and physical methods of how the CO 2 could be removed from the atmosphere. The processes proposed so far are slow, they would require a large-scale industrial use of probably more than a hundred years in order to reduce atmospheric CO 2 concentrations significantly.

Depending on the CDR technology, different reservoirs serve to store the carbon removed from the atmosphere. Reservoirs differ in their storage capacity and the length of time they store carbon. Reservoirs in which carbon has been trapped for at least tens of thousands of years are called permanent . The storage of carbon in non-permanent reservoirs has a retarding rather than a preventive effect on global warming. Geological reservoirs could permanently store the carbon, while land- or ocean-based reservoirs are not considered permanent. In the case of land-based reservoirs (soils, biosphere) in particular, there is also the risk that CO 2 will be released more quickly again if the climate changes . Geological and oceanic reservoirs could hold several thousand gigatons (Gt) of carbon, land-based reservoirs roughly 200 Gt. For comparison: The energy-related CO 2 emissions - i.e. without cement production, land use changes and without other greenhouse gases - amounted to around 32.5 Gt in 2017, which corresponds to around 8.9 Gt of carbon.

Currently, the oceans and the biosphere are rapidly absorbing around half of human CO 2 emissions from the atmosphere. As a result, on the one hand, they dampen the rise in atmospheric CO 2 concentrations, and on the other hand, the oceans become acidic and have effects on plant growth. Unlike solar radiation management, carbon dioxide removal also counteracts these two effects: If the CO 2 concentration fell, the oceans and the biosphere would release part of the stored CO 2 back into the atmosphere. Because of this rebound effect, about twice as much CO 2 has to be removed with CDR for a desired CO 2 reduction in the atmosphere .

Increased production of biomass and storage on land

These are biological processes that aim to increase the production of biomass and store the carbon bound in this way in the biosphere or soils. In order to bind the carbon for a longer period of time, it must be removed from the carbon cycle, for example in the form of wood.

The processes include modified soil cultivation in agriculture, bioenergy with CO2 capture and storage (BECCS), afforestation or rewetting of moors.

There are a number of limiting factors for these processes: limited agricultural land, scarce nutrients or the availability of water. The large-scale use of BECCS in specially operated plantations would very likely bring the earth system closer to its capacity limit in terms of freshwater use ; with regard to land use changes , the integrity of the biosphere and biogeochemical cycles, the planetary boundaries would be exceeded even further than they are now (see Planetary Boundaries ).

Many model calculations that show how global warming can be limited to below 2 ° C generally assume the availability of BECCS technologies in the second half of this century. The land consumption for the cultivation of biomass is in typical scenarios about 1.2 times the area of India , which is why the future use of BECCS - at least on this industrial scale - is highly speculative.

Increased production of biomass and storage in the oceans

These biological processes are designed to stimulate biomass production in the oceans. The growth of phytoplankton is stimulated, part of the carbon bound in this way is transported with the dead plankton into the deep sea.

The geochemist James Lovelock suggested stirring up the upper ocean layers. This brings nutrients to the surface of the sea and stimulates algae growth. The algae in turn absorb carbon dioxide from the atmosphere and thus reduce the greenhouse effect . Algae growth could also be stimulated with the help of sea ​​fertilization ; dying algae sink to the sea floor and thus withdraw the bound CO 2 from the sea and thus indirectly from the atmosphere. However, experiments by the Alfred Wegener Institute in 2000 ( EisenEx experiment ) and in spring 2009 ( LOHAFEX experiment ) have shown that the effect is only very slight, since the algae are almost completely eaten by animal organisms before they die then exhale the CO 2 again.

These experiments carry the risk of undesirable side effects on marine fauna. In addition, they could violate the moratorium on ocean fertilization adopted at the 9th Conference of the Parties to the Biodiversity Convention . However, the danger of creating large, oxygen-poor marine regions mentioned in this opinion was already pointed out in the early 1990s.

Accelerated weathering

In the weathering of silicate and carbonate rocks , carbon is bound. These processes are extremely slow. There are proposals to accelerate the weathering process on land, for example by spreading artificially produced rock flour from silicate minerals over a wide area.

CO 2 absorbed by the oceans reacts - over very long periods of time - with carbonate sediments on the sea floor. Artificial liming of the seas could intensify this process. Also in the artificial alkalization of oceans ( Artificial Ocean Alkalinization ) is expected to Terminationseffekt. According to simulation calculations, the sudden end of such a large-scale project would cause rapid regional warming and acidification, which would occur much faster than caused by global warming.

Other CDR methods

The considerations of direct air capture consist in extracting CO 2 directly from the ambient air using chemical processes. The extraction would take place via absorption with solids, with highly alkaline solutions or with alkaline solutions using a catalyst . This CO 2 would be stored in geological or oceanic reservoirs.

The efficiency of this process is limited by the low concentration of CO 2 in the air. Because of the higher concentration, CO 2 capture and storage directly at the emission source is considered to be more promising.

Another idea that combines different approaches is called the ISA procedure . It is described as a nature-identical method (see loess dust in the Ice Age) for climate cooling by introducing airborne dust particles into the troposphere, which consist of iron oxide or optionally iron chloride. This is intended to cause the breakdown of substances that have an impact on the climate - methane, soot, ozone and volatile organic compounds - and an increase in cloud cover reflection. The idea is that the precipitation of the mineral dust will accelerate biomass production and storage on land and in the oceans. Established greenhouse gas emitters (primarily aircraft, but also power stations and ships) can be used to transport the particles into the atmosphere. Iron-containing fuel additives are technically fed into the combustion processes with minimal effort.

Other suggestions

High cirrus clouds have a warming effect on the climate. The introduction of certain ice crystals as cloud condensation nuclei by airplanes could change their properties in such a way that more of the long-wave heat radiation leaves the atmosphere through them.

There are several suggestions for slowing down the melting of polar sea ​​glaciers and thus the rise in sea levels :

  • Seawater barriers in front of glacier tongues could reduce the thawing effect caused by circulating water.
  • Artificial islands at the end of the glacier tongue could slow the flow of ice.
  • Pumping stations on the ice behind the glacier touchdown line could pump out or freeze water that accelerates the flow of the ice at the bottom of the glacier.

This geoengineering proposal is not about climate engineering, but about countering the serious consequences of warming in order to buy time.

hazards

In 2008, the climate scientist Alan Robock compiled and published a 20-point list of possible dangers when using geoengineering. He concludes that at least 13 of the 20 points represent side effects and threats to the climate system and the environment.

  • Regional temperature changes
  • Changes in precipitation patterns
  • Damage to the ozone layer (with aerosol geoengineering)
  • No reduction in the CO 2 content of the atmosphere (with SRM methods)
  • No prevention of ocean acidification
  • Negative effects on flora and fauna
  • Reinforcement of acid rain (when sulfur dioxide is applied)
  • Effects on natural (cirrus) clouds
  • Bleaching of the sky
  • Lower power output for solar systems
  • Sharp rise in temperature when project has to be stopped
  • Human or technical failure
  • Unknown, unpredictable effects
  • Negative impact on the willingness to CO 2 reduction
  • Abuse for military purposes
  • Risk of commercial control of the techniques
  • Contradiction to the ENMOD convention
  • Possibly extremely high costs (exception: aerosol geoengineering)
  • Need for supranational control
  • No decision-making framework in place
  • Incompatible conflicts of interest of individual states (who determines the global temperature?)
  • Considerable potential for conflict (political, ethical, moral )

Particular dangers arise if geoengineering measures to cool the earth are abruptly interrupted. In this case, the global average temperature can increase extremely by 2 to 4 ° C per decade, i.e. a warming at a 20-fold rate compared to the current one.

If, for example, radiation management (SRM) measures take place at a distance of more than 120 km from Earth and thus in space , space liability law would generally apply in the event of damage . But compensation for environmental damage has not yet been provided for, especially in the Space Liability Convention (WHÜ), and neither is damage in non-state areas such as the Antarctic.

Geoengineering under discussion

In the 1960s, geoengineering was sometimes viewed euphorically as an opportunity for “beneficial changes”. I.a. the following "great projects" were proposed:

  • Blackening the Arctic ice with the help of carbon (the lower radiation loss should make the wasteland of the far north habitable)
  • Applying a thin layer of 1-hexadecanol to the oceans (the lower evaporation should mitigate tropical storms, albeit at the cost of warming seawater)
  • Ignition of ten "clean" hydrogen bombs of ten megatons each under the Arctic Ocean (the rising steam of the explosion cloud should freeze in the upper atmosphere and thus reduce heat radiation; hoped-for effect: "This could change the general air circulation on earth and widen the climate Areas of the world might be improved ")
  • Construction of a dike in the Bering Strait as well as nuclear power plants to pump cold water into the Pacific (hoped-for effect: "Warm water from the Atlantic would flow after the cold water and thus improve the weather in the Arctic")

Today, geoengineering is met with great skepticism in public, especially in Europe. A popular belief is that geoengineering would undermine efforts to focus on the root cause of the greenhouse gas emissions problem. Most scientists also believe that unknown risks are dangerous. There are also ethical reservations. On the other hand - so an argument of the geoengineering proponents - emergency situations could arise which make it appear necessary to research ultima ratio options in order to have them available if necessary ("arming the future").

According to the Royal Society , geoengineering is not an alternative to emissions reductions, which should be the top priority. However, since these reductions are proving difficult, some geoengineering approaches could help. Due to the still great uncertainties regarding the effectiveness, costs as well as social and environmental effects, significantly more research is necessary. In addition, the public must be included in the discussion and a regulatory system created. For the purpose of this international cooperation and the creation of an international set of rules to ensure transparent and responsible GE research, the Royal Society, the Academy of Sciences for the Developing World (TWAS) and the Environmental Defense Fund (EDF) the platform "Solar Radiation Management Research Governance Initiative" (SRMGI) founded. An interdisciplinary study was started in Heidelberg in August 2009 under the motto “The global governance of climate engineering” .

The climate researcher Michael E. Mann is critical of geoengineering because of the associated consequences, which under certain circumstances could be even more severe than the consequences of global warming. It could be possible that a situation arises that could necessitate emergency measures in the form of geoengineering in order to prevent even worse effects of climate change. However, he points out that geoengineering is now mainly brought into the political debate by those who have a strong interest in the continued use of fossil fuels and, for economic or ideological reasons, climate protection measures such as reducing greenhouse gas emissions , expanding renewable energies or reject the introduction of a CO 2 price . Geoengineering is "the logical way out, especially for supporters of free market fundamentalism, because it reflects an extension of the belief that the free market and technological innovations can solve every problem we create without the need for regulation." In order not to have to initiate climate protection measures, geoengineering such as the heroin substitute methadone would be presented as a supposedly simple cure for climate change. The main cause of climate change is known: carbon dioxide emissions. The "simplest and safest solution" is to "get to the root of the problem", not to rely on geoengineering and thereby risk the "earth's climate system and the sensitive, complex network of ecosystems that it supports" is more damaged.

A study by the Kiel Earth Institute, commissioned by the German government, also comes to the conclusion that the use of geoengineering can be accompanied by "considerable side effects, the extent of which, however, is still largely unknown". So far, research into the side effects of geoengineering has received little attention. Also, "social science research [...] has hardly dealt with the social aspects of the use of climate engineering." In addition, research on political, legal and economic aspects associated with geoengineering is still in the early stages.

The German political scientist Elmar Altvater points out that such a complex challenge cannot be solved with a one-dimensional approach, but only holistically : "... because geoengineering means exactly what the name says: an engineering and not a holistic approach."

In its special report Development and Justice through Transformation , the German Advisory Council on Global Change (WBGU) recommends not taking any measures aimed at manipulating the global radiation budget, and recommends that the G20 take a critical stance on geoengineering.

At the 10th Conference of the Parties to the Convention on Biological Diversity, environmental organizations pressed for a moratorium on a ban on geoengineering projects. In accordance with the decision to ban marine fertilization (COP 9, IX / 16 C), the decision was made to refrain from geoengineering activities until there is a comprehensive scientific basis that ensures that such activities cannot have a damaging impact on the environment and biodiversity . Small-scale research studies were explicitly excluded, however, provided that they can be justified by the need to acquire further research knowledge, are in accordance with Article 3 of the Convention and, in addition, a thorough, prior assessment has been carried out with regard to possible impacts on the environment.

fiction

  • In the film Snowpiercer , geoengineering was practiced by spraying chemicals into the upper atmosphere. The result is a snowball earth ; a global ice age that made almost all life extinct.

literature

  • Werner Arber : Predictability in science. Accuracy and limitations. In: The Proceedings of the plenary session , November 3-6, 2006. Pontifical Academy of Sciences , Vatican City 2008, ISBN 978-88-7761-094-2 , ( Pontificiae Academiae Scientiarum acta 19), pp. 83-97.
  • Paul J. Crutzen : An Example of Geo-Engineering. Cooling Down Earth's Climate by Sulfur Emissions in the Stratosphere.
  • Jeff Goodell: How to Cool the Planet. Geoengineering and the Audacious Quest to Fix Earth's Climate. Houghton Mifflin Harcourt, Boston MA 2010, ISBN 978-0-618-99061-0 .
  • Eli Kintisch: Hack the Planet: Science's Best Hope - or Worst Nightmare - for Averting Climate Catastrophe . Wiley, 2010. ISBN 0-470-52426-X .
  • Brian Launder and J. Michael T. Thompson (Eds.): Geo-engineering climate change. Environmental necessity or Pandora's box? Cambridge University Press. Cambridge 2010. ISBN 978-0-521-19803-5 .
  • political ecology: geoengineering. Necessary plan B against climate change? With contributions by O. Renn, K. Ott, P. Mooney, A. Grundwald, A. Oschlies, U. Potzel, and many more, issue 120, oekom Verlag Munich 2010, ISBN 978-3-86581-226-1 .
  • Gernot Wagner and Martin L. Weitzman : Klimaschock , Vienna, Ueberreuter non-fiction book 2016, ISBN 978-3-8000-7649-9 .

Web links

Commons : Climate engineering  - collection of images, videos and audio files

Individual evidence

  1. ↑ a b c d Leon Clarke, Kejun Jiang et al. a .: Assessing Transformation Pathways . In: Otmar Edenhofer u. a. (Ed.): Climate Change 2014: Mitigation of Climate Change. Contribution of Working Group III to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change . 2014, 6.9 Carbon and radiation management and other geo-engineering options including environmental risks, p. 484-489 .
  2. ↑ Intergovernmental Panel on Climate Change (IPCC): Special Report on 1.5 ° C Global Warming (SR1.5), - Summary for Policy Makers. [de-ipcc.de], 2018, accessed on December 17, 2019 .
  3. ↑ a b c d e f g h i Hauke ​​Schmidt and Rüdiger Wolfrum: Targeted interventions: Climate engineering from a climate science and international law perspective . In: Jochem Marotzke and Martin Stratmann (eds.): The future of the climate: New findings, new challenges, a report by the Max Planck Society . CH Beck, 2015, ISBN 978-3-406-66967-5 , pp. 183-200 .
  4. ^ President's Science Advisory Committee (Ed.): Restoring the Quality of Our Environment. Report of the Environmental Pollution Panel. Washington, DC 1965, p. 9: 111-131 ( handle.net ).
  5. ↑ Stephen H. Schneider : Geo-engineering: could we or should we make it work. In: Brian Launder: Geo-engineering climate change-environmental necessity or Pandora's box? Cambridge University Press , Cambridge 2010, ISBN 978-0-521-19803-5 : “ This term was informally coined in the early 1970s by Cesare Marchetti (and formally published at the invitation of the editor of Climate Change in its inaugural issue as Marchetti 1977). ”P. 5.
  6. ↑ a b c d e f g h Olivier Boucher u. a .: Rethinking climate engineering categorization in the context of climate change mitigation and adaptation . In: WIREs Climate Change . tape 5 , no. 1 , 2014, doi : 10.1002 / wcc.261 .
  7. ↑ Original article : Cesare Marchetti: On geoengineering and the CO 2 problem . In: Climatic Change . tape 1 , no. 1 , March 1977 ( draft version [PDF; 498 kB ]).
  8. ^ Institute of Medicine, National Academy of Sciences, and National Academy of Engineering: Policy Implications of Greenhouse Warming: Mitigation, Adaptation, and the Science Base . 1992, ISBN 978-0-309-04386-1 , doi : 10.17226 / 1605 ( nap.edu [accessed February 10, 2019]).
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  65. ↑ Solar Radiation Management Research Governance Initiative (SRMGI)
  66. ↑ On "Climate Engineering" from a natural, social and legal perspective:  ( Page no longer available , search in web archives )  Info: The link was automatically marked as defective. Please check the link according to the instructions and then remove this notice.@1@ 2Template: Dead Link / www.fona.de  
  67. ↑ Michael E. Mann , Tom Toles: The madhouse effect. How climate change denial threatens our planet, destroys our politics and drives us insane . Erlangen 2018, p. 134f; ibid. p. 145.
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