What is geoengineering?

"Geoengineering" or "climate engineering" may be defined as the deliberate large-scale manipulation of climate. The study of such techniques has been proposed in order to prepare for the cases that attempts to limit projected climate change by the reduction of greenhouse gas concentrations may fail or that consequences of climate change may prove worse than expected.

In general two main classes of geoengineering techniques are distinguished:

1) Carbon dioxide removal techniques (CDR) address the root cause of climate change by removing greenhouse gases from the atmosphere:

• Technical capture of carbon from the atmosphere

•  Ocean fertilization to enhance uptake by biological systems

2) Solar Radiation Management techniques (SRM) reflect sun light and heat back into space. They attempt to offset effects of increased greenhouse gas concentrations by causing the Earth to absorb less solar radiation.

• Increasing the surface reflectivity of the planet, by brightening human structures (eg by painting them white), planting of crops with a high reflectivity, or covering deserts with reflective material;
• Enhancement of marine cloud reflectivity;
• Placing shields or deflectors in space to reduce the amount of solar energy reaching the Earth;
• Mimicking the effects of volcanic eruptions by injecting sulfate aerosols into the lower stratosphere.

Why do we study geoengineering?

Geoengineering may result in undesirable side effects for crucial parts of the Earth system and humankind.  Therefore it is necessary to study the possible efficiency, risks and implications. Numerical models are the only possible tool for performing initial scientific studies. Three complex climate models will be used to quantify the effectiveness and side effects of such geoengineering concepts aiming at a reduction of the incoming solar radiation.