IT has taken about twenty-five years for the world to progress from almost complete ignorance about global warming and climate change to the point today when there is a widespread acceptance of the risk that these linked phenomena represent for this planet's future. But those citizens keen to take an active interest in supporting measures for holding back climate change must be increasingly confused by the variety of advice -- some of it conflicting -- being offered on which projects should have priority. In the relatively simple area of renewable energy, for instance, the advocates of solar and wind power disagree strongly about the advantages of their respective systems. So-called “clean coal” has its advocates but its opponents claim that more energy has to be used in the cleaning process than is ultimately released from power generation. There are, however, certain measures of such importance that they override all others. One of these is the preservation of the world's existing rainforests which are a front line defence because of the highly efficient way in which they absorb the greenhouse gases that lead to global warming. This week in London Prince Charles has been hosting a Nobel Laureate Symposium on rainforest protection. The Prince's Rainforest Project is bringing together governments, environmentalists and business in an important effort to preserve the rainforests and restore the damage already done to them. It is an admirable initiative.