Warmer winters

SIR – Christopher Booker, discussing climate change (The Last Word, January 7), is wrong to claim that this year “is the latest in a succession of recent record cold winters” in North America.

According to the United States National Oceanic and Atmospheric Administration, the coldest winter on record for the contiguous United States was in 1978-79, followed by 1935-36, 1898-99, 1909-10 and 1904-5.

Seven of the 10 past winters have been warmer than average, including the warmest winter on record in 2015-16. The winters of 2007-08 and 2013-14, which Mr Booker highlights as particularly cold, were respectively only the 68th and 33rd coldest since records began in 1901. The mean temperature for the US in December 2017 was above average.

Similarly, according to the Canadian government’s environment department, the coldest winters since national records began in 1948 were in 1971-72, 1949-50, 1956-57, 1964-65 and 1948-49. Nine of the past 10 winters have been warmer than average, and the five warmest years have all occurred since 2006.

Mr Booker also asserts that diesel is “the most heavily CO2-emitting fuel of them all”. According to the United States Energy Information Administration, coal generates significantly more CO2 per unit of energy output than diesel. Bob Ward

Policy and Communications Director, Grantham Research Institute on Climate Change and the Environment, London School of Economics