|Sun Dogs in Fargo North Dakota|
Astronomers have ruled out the possibility of the early dawn being a result of a shift of the earth's axis and Thomas Posch, of the Institute for Astronomy of the University of Vienna, says a change in the horizon is "by far the most obvious explanation".
According to to the National Climatic Data Centre in North Carolina, 2010 was the warmest year on record and a separate report from the World Meteorology Organisation found that temperatures in Greenland were 3C above average last year.
However, not everyone accepts the explanation that melting glaciers are to blame. Message-boards are full of posts from conspiracy theorists blaming everything from chemtrails to a build-up of methane in the atmosphere or a shift in the earth's axis.
That last idea has been pooh-poohed by Wolfgang Lenhardt, director of the department of geophysics at the Central Institute for Meteorology in Vienna, who explains: "The data of the earth's axis and rotation are monitored continuously and meticulously and we would know if that had happened... there would have been an outcry around the world."
However he does suggest one other possible explanation - that ice crystals in the air had refracted the sun's light creating a mirage, known as a sun-dog, which appeared above the horizon.