Man is the sole being to have changed the face of the Earth. In February, the largest meeting of scientists ever organized by the United Nations said that carbon dioxide and other greenhouse gases were responsible for the phenomenon of global warming. In April, the same network of some 2,000 scientists concluded that the phenomenon was having an impact on weather conditions, the oceans and the environment. A major UN climate report published yesterday said that sweeping cuts in greenhouse gas emissions over the next 50 years to keep global warming in check was technologically possible and would cost only a tiny fraction of world economic output. What we need to do is change our habits on a national as well as individual level. Time will tell if, after changing the Earth, man will also be able to save it.