Media outlets often cite local and regional heatwaves, cold spells, and other weather extremes as evidence for and against global warming, but such isolated events provide no proof one way or another. This is because anecdotes are not reliable indicators of global temperatures, and a leaked 2001 email from a leading climate scientist reveals: "There are huge differences between different regions - Alaska has warmed substantially while eastern North America cooled after the 1950s. Locking onto local records, no matter how beautiful, can lead to serious errors." The entire United States contains only 1.9% of the world's surface area, but a 2008 survey of Virginia residents found that the most common answer people give for believing or disbelieving in global warming is their personal experience of the climate.