Schemes to tackle climate change could prove disastrous for billions of people, but might be required for the good of the planet, scientists say. That is the conclusion of a new set of studies into what's become known as geo-engineering. This is the so far unproven science of intervening in the climate to bring down temperatures. These projects work by, for example, shading the Earth from the Sun or soaking up carbon dioxide. Ideas include aircraft spraying out sulphur particles at high altitude to mimic the cooling effect of volcanoes or using artificial "trees" to absorb CO2. Long regarded as the most bizarre of all solutions for global warming, ideas for geo-engineering have come in for more scrutiny in recent years as international efforts to limit carbon emissions have failed. Now three combined research projects, led by teams from the universities of Leeds, Bristol and Oxford, have explored the implications in more detail. The central conclusion, according to Dr Matt Watson of Bristol University, is that the issues surrounding geo-engineering - how it might work, the effects it might have and the potential downsides - are "really really complicated". Details via BBC News.