• In the article “Alps are no go without snow” (24 May, p 18) we said the measurement stations are between 200 and 1800 metres above snow level: that should have been above sea level. The study counted snow days, not snowfall; and the 60 per cent decline was for the Swiss plateau between Zurich, Bern and Basel, and not the Swiss Alps.
• In the graph accompanying the article on food supply (14 June, p 28) world population should have been in billions, not millions.
• We said that the Transpolar Drift Stream was driven by westerly winds (7 June, p 42). They are easterlies, blowing from the east.
