Environment Counts | Climate engineering
Unless future efforts to reduce greenhouse gas emissions are much more successful then they have been so far, deliberate large-scale intervention in the Earthâ€™s climate system may be required to moderate global warming.
The report emphasizes that the safest and most predictable method of moderating climate change is to reduce emissions of greenhouse gases and that geoengineering methods are not the silver bullet for addressing climate change.
The report says that geoengineering methods could potentially be used to complement continuing efforts to mitigate climate change. The report is optimistic that geoengineering the Earthâ€™s climate is feasible, but warns that there are major uncertainties regarding its effectiveness, costs, and environmental impacts. In particular there are serious and complex governance issues which need to be resolved if geoengineering is ever to become an acceptable method for moderating climate change.
The report divides geoengineering technology into two types of methods.
Carbon dioxide removal (CDR)
Carbon dioxide removal techniques address the root cause of climate change by removing greenhouse gases from the atmosphere.
CDR methods reviewed by the report include
- Land use management to protect or enhance land carbon sinks
- The use of biomass for carbon sequestration as well as a carbon neutral energy source
- Enhancement of natural weathering processes to remove CO2 from the atmosphere
- Direct engineered capture of CO2 from ambient air
- Enhancement of oceanic uptake of CO2, for example, by fertilization of the oceans with naturally scarce nutrients, or by increasing upwelling processes.
Solar Radiation Management (SRM)
Solar radiation management techniques attempt to offset effects of increased greenhouse gas concentrations by reflecting solar radiation causing the Earth to absorb less heat.
SRM techniques directly modify the Earthâ€™s radiation balance, and would take only a few years to have an effect on climate once they had been deployed. They do not treat the root cause of climate change but because they act quickly, they could be useful in an emergency, for example to avoid reaching a climate â€˜tipping pointâ€™.
SRM methods assessed in the report include
- Increasing the surface reflectivity of the planet, by brightening human structures, planting crops with a high reflectivity, or covering deserts with reflective material
- Enhancement of marine cloud reflectivity
- Mimicking the effects of volcanic eruptions by injecting sulphate aerosols into the lower stratosphere
- Placing deflectors in space to reduce the amount of solar energy reaching the Earth
The report’s overall recommendations are
â€¢ Nations should increase effort towards mitigating and adapting to climate change, and in particular to reduce global emissions by least 50% compared to 1990 levels by 2050 and by more after 2050
â€¢ Research and development of geoengineering alternatives should be undertaken to investigate the feasibility of using low risk methods if it becomes necessary to reduce the rate of warming this century.