Geoengineering, the deliberate large-scale engineering and manipulation of the planetary environment, is not only for the realm of science fiction but a current day reality. Researchers have proposed that geoengineering could be used to combat the impact humans have made on the environment. A European effort involving scientists from all over Europe investigated the precise impact that some suggested geoengineering projects would have, and the results may not be want we want. 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).
Tackling climate change through geoengineering is an ambitious desire. Various small-scale projects have already got off the ground, such as tree planting efforts to redress climate change. But no large-scale plans have begun as scientists are uncertain what the results would be. Some researchers believe the reduction of the solar radiation reaching our planet using climate engineering could work. This, however, could result in adverse effects for Earth and humankind, others say. In this latest study, French, German, Norwegian and British scientists observed that disruption of global and regional rainfall patterns is 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 revealed 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 simply mimicking the effects of large volcanic eruptions. This can be mimicked by releasing sulphur dioxide into the atmosphere or by deploying giant mirrors in space, according to the researchers.
While ideas to combat climate change exist, the researchers 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 Institut Pierre Simon Laplace in France, and the Max Planck Institute in Germany. Norwegian scientists developed the fourth Earth model used.
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