atmosphere of the EarthClick to enlarge
Interventions in the complex structure of the atmosphere can have incalculable consequences.
Source: Kobes /

A number of ideas have emerged in recent years for potential interventions in the climate system to counteract global warming. What these so-called geoengineering measures all have in common is that they harbour risks for humans and the environment and can have a global impact. They should therefore also be regulated globally.

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What is geoengineering?

Geoengineering refers to “the deliberate large-scale intervention in the Earth’s climate system in order to counteract man-made (anthropogenic) climate change” (Royal Society 2009). Instead of fighting the causes (anthropogenic greenhouse gas emissions) of climate change, geoengineering can in fact only influence or mitigate its impacts. Interventions are usually classified into two groups:

  1. Solar Radiation Management – SRM
    The aim of these approaches is to limit the sun's radiation onto the Earth’s surface and reduce global average temperature. This includes methods such as installing mirrors in space or increasing the reflectivity of the earth’s surface (albedo), for example by painting the roofs of settlements white. The most commonly discussed approach in the literature is the injection of liquid droplets (aerosols) into the stratosphere to scatter sunlight and thereby reduce solar radiation reaching the Earth’s surface.
  2. Carbon Dioxide Removal - CDR
    This approach aims to reduce the concentration of CO2 (a greenhouse gas) in the atmosphere. This is done by removing carbon dioxide from the atmosphere and, if possible, from the entire carbon cycle (e.g. through underground storage). Plants remove carbon dioxide (CO2) during photosynthesis and store carbon in biomass. However, the CO2 is released again when the biomass is burned or decays. A few CDR approaches seek to take advantage of these natural processes. Some onshore examples are large-scale afforestation activities, or the use of bioenergy combined with carbon capture and storage, also known as BECCS. An example of an offshore approach is ocean fertilisation, which promotes algal bloom and thereby captures greater amounts of CO2. Other approaches apply chemicals and intensive energy to imitate these natural processes, for example through direct air capture with carbon storage (DACCS) technology. Other methods rely on chemical reactions between the atmosphere and rocks (enhanced weathering).

Effective climate protection or megalomania?

UBA published a systematic analysis of geoengineering methods in 2011. The publication Geoengineering – effective climate protection or megalomania? addresses geoengineering on the basis of the precautionary principle. Therefore, it does not recommend the application of geoengineering methods because all the considered approaches entail potential resource conflicts  and unpredictable global risks. Furthermore, most potential methods are either in the early stages of development or merely theoretical considerations and therefore unavailable.
Geoengineering measures seem attractive because a technical solution to the climate problem makes "business as usual" possible and efforts to reduce emissions less urgent. The application of geoengineering measures could however lead to a paradigm shift in three respects, which the German Environment Agency principally rejects: firstly, the assumption that humans are in a position to understand and control global environmental processes; secondly, the assumption that geoengineering can replace mitigation and adaptation measures; thirdly, a policy shift leading to fundamental principles of international environmental law being thrown overboard such as emissions reductions.

The consensus that has existed up to now that large-scale greenhouse gas mitigation activities are necessary could be cast into doubt. There is a risk that combating the causes (excessive levels of greenhouse gas emissions) will be neglected in favour of so-called rescue measures which are supposedly available. There is also the risk that humanity will be confronted with the effects of dangerous climate change as well as the negative impacts of geoengineering.


Need for global regulation of geoengineering

Because a state's geoengineering measures can have global impact, global regulation is necessary. Even field research activities can have a negative effect, for example as a result of large-scale field tests in the atmosphere. No geoengineering measures have been taken up to now, but researchers have been exploring theoretical approaches such as modelling or laboratory research. Several of the CDR technologies have been tested (e.g. DACCS and BECCS). Researchers have plans to implement the first SRM measures in North America. This is proof that some form of global regulation is already necessary.

Fertilisation of the oceans to promote algal bloom for CO2 sequestration is the only geoengineering measure to date for which there is internationally binding legislation. According to the precautionary principle, however, all geoengineering activities that harbour transboundary risks must be subject to an international ban. This concerns among others the release of sulphur compounds into the stratosphere to reduce solar radiation on the Earth’s surface. Exceptions should be made for the purpose of research only.


Comprehensive global control mechanism under the Convention on Biological Diversity?

The Convention on Biological Diversity (CBD) could provide the statutory framework for an international exchange and development of guidelines for global control of geoengineering. Under the umbrella of the Convention 196 Contracting Parties agreed in 2010 at least temporarily on a moratorium on geoengineering, but it does not cover certain specific forms of carbon storage. The Contracting Parties reaffirmed the ban in 2016. The German Environment Agency has compiled a fact sheet (in German) on this “de facto moratorium”.


Geoengineering in the oceans: Regulation under the London Protocol

Ocean fertilisation is a hotly debated method. The basic idea is to trigger algal bloom across large areas by introducing considerable quantities of iron compounds into the ocean. The CO2 captured in the algae sinks to the ocean floor once the algae die off. Experiments have thus far failed to prove the theoretical assumptions about the potential of ocean fertilisation for CO2 storage. In addition, the practice harbours significant risks as a result of the input of additional pollutants to the oceans.
43 states agreed in 2013 on a binding international regulation, which includes a ban on commercial research projects.