A geoengineering solution to climate change could lead to significant rainfall reduction in Europe and North America, scientists say.
The scientists from Germany, Norway, France and the UK studied how four Earth models responded to climate engineering in a world with a CO2 concentration four times higher than preindustrial levels, but where the extra heat caused by such an increase is balanced by a reduction of radiation from the sun.
Hauke Schmidt, lead author, said quadrupling of CO2 was at the upper end, but still in the range of what was considered possible at the end of the 21st century.
The study found that global rainfall fell by about five per cent on average in all four models. Under the scenario studied, rainfall diminished by about 15 per cent, or about 100 millimetres per year, compared to pre-industrial levels, in large areas of North America and northern Eurasia. Over central South America, all the models showed a decrease in rainfall that reached more than 20 per cent in parts of the Amazon region.
"Climate engineering cannot be seen as a substitute for a policy pathway of mitigating climate change through the reduction of greenhouse gas emissions," they said in the study, published in Earth System Dynamics, an open access journal of the European Geosciences Union.
Geoengineering projects range from mimicking the effects of large volcanic eruptions by releasing sulphur dioxide into the atmosphere, to deploying giant mirrors in space to deflect the sun's rays. Proponents say they could be a rapid response to rising global temperatures but environmentalists argue they are a distraction from the need to reduce man-made carbon emissions. Critics also point to a lack of solid research into unintended consequences and the absence of any international governance structure for such projects, whose effects could transcend national borders.