|Large-scale engineering projects aimed at fighting global warming could
radically reduce rainfall in Europe and North America, a team of
scientists from four European countries have warned.
Geoengineering projects are controversial, even though they are largely
theoretical at this point. They range from mimicking the effects of
volcanic eruptions by releasing sulphur dioxide into the atmosphere, to
deploying giant mirrors in space to deflect the sun's rays.
In this new study scientists from Germany, Norway, France and the UK
used four different computer models that mimic the earth's climate to
see how they responded to increased levels of CO2 coupled with reduced
radiation from the sun. Their scenario assumed a world with four times
the CO2 concentration of the preindustrial world, which is in the range
of what is considered possible at the end of this century.
They found that global rainfall was reduced by about 5% on average using
all four models. Under the scenario studied, rainfall diminished by
about 15%, 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% in parts of the Amazon region.