Scientists Sound Caution On Geoengineering


(CORDIS) — Geoengineering, the deliberate large-scale engineering and manipulation of the planetary environment, is not only for the realm of science fiction but a potentially realistic option to mitigate climate change.

In an era where the earth’s climate is influenced by human activity on a global scale, researchers have proposed that specific targeted technologies could be developed and used to countervail the change. A European effort involving scientists from all over Europe investigated the impacts that some suggested geoengineering options would have, and the results may not exactly be what was intended. Presented in the journal Earth System Dynamics, the research was funded in part by the IMPLICC (‘Implications and risks of engineering solar radiation to limit climate change’) project, which has received almost EUR 1 million under the Environment Theme of the EU’s Seventh Framework Programme (FP7).

Some scientists have formerly argued that using target technologies like injection sulphur aerosol into the stratosphere to reduce solar irradiation could be more effective and less costly than attempts to reduce greenhouse gas emissions in order to combat climate change. Also, some say it might become necessary to use geoengineering technologies to prevent us from abrupt catastrophic changes of the climate system. While others doubt the effectiveness of such options and argue with unwanted side effects, as well as legal and ethical aspects against geoengineering, some researchers, politicians and economists believe the reduction of the solar radiation reaching our planet using climate engineering could work.

In order to put the discussion on a more sound scientific basis, French, German, Norwegian and British scientists used sophisticated climate models and observed for instance that significant reductions of global and regional rainfall patterns are likely in a geoengineered climate.

‘Climate engineering cannot be seen as a substitute for a policy pathway of mitigating climate change through the reduction of greenhouse gas emissions,’ the authors write in the paper. This suggests that this geoengineering solution to climate change could lead to significant rainfall reduction in both Europe and North America.

Led by the Max Planck Institute for Meteorology in Germany, the researchers scrutinized how models of Earth in a warm, carbon dioxide (CO2)-rich world respond to an artificial reduction in the amount of sunlight reaching the planet’s surface.

Geoengineering techniques could be used to reduce the amount of solar radiation reaching Earth’s surface range by mimicking the effects of large volcanic eruptions which do have global cooling effects on climate. The same could be achieved by releasing sulphur dioxide into the atmosphere or by deploying giant mirrors in space, the researchers suggest.

While ideas to combat climate change exist, the scientists focused their efforts on studying the expected impact of their implementation. To achieve this, they examined how four Earth models responded to climate engineering under a specific scenario.

Their hypothetical scenario assumed a world with a CO2 concentration that is four times higher than preindustrial levels, but where the extra heat caused by such an increase is balanced by a reduction of radiation we receive from the Sun.

‘A quadrupling of CO2 is at the upper end, but still in the range of what is considered possible at the end of the 21st century,’ says Hauke Schmidt from the Max Planck Institute for Meteorology and lead author of the paper.

They observed a reduction in rainfall by 100 millimetres per year, roughly a 15% drop of preindustrial precipitation values in large areas of North America and northern Eurasia. Meanwhile, over central South America, all models show a decrease in rainfall that reaches more than 20% in parts of the Amazon region. Overall, global rainfall is reduced by about 5% on average in all four models studied.

‘The impacts of these changes are yet to be addressed, but the main message is that the climate produced by geoengineering is different to any earlier climate even if the global mean temperature of an earlier climate might be reproduced,’ says Dr Schmidt.

The researchers are, however, quick to note that the scenario studied is not intended to be realistic for a potential future application of climate engineering. But the experiment allows the team to clearly identify and compare basic responses of Earth’s climate to geoengineering, laying the groundwork for more detailed future studies.

Says Dr Schmidt: ‘This study is the first clean comparison of different models following a strict simulation protocol, allowing us to estimate the robustness of the results. Additionally we are using the newest breed of climate models, the ones that will provide results for the Fifth IPCC [Intergovernmental Panel on Climate Change] Report.’

The scientists used climate models developed by the UK Met Office’s Hadley Centre, the Institute Pierre Simon Laplace in France, and the Max Planck Institute in Germany. Norwegian scientists developed the fourth Earth model used.

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