According to the UK’s Optimum Population Trust, the cheapest solution to climate change is population control: “The cost-benefit analysis commissioned by the trust claims that family planning is the cheapest way to reduce carbon emissions. Every £4 spent on contraception, it says, saves one tonne of CO2 being added to global warming, but a similar reduction in emissions would require an £8 investment in tree planting, £15 in wind power, £31 in solar energy and £56 in hybrid vehicle technology.” (see The Guardian 3 December). The full report and press release of the Trust are available via their website.