'What we do know is that 'normal' is slowly changing. The National Weather Service defines the warmest 30% of the seasons in the period of climatology as 'warmer than normal' and the coldest 30% as 'cooler than normal.' In the 1980s it was predicted that, because of increasing human-made greenhouse gases, the percentage of 'warmer than normal' seasons would increase to 60-70% by the beginning of the 21st century. That is just what has happened, as typically 60-70% of the meteorological stations around the world now report 'warmer than normal' in any given season.'
Please see:
http://www.giss.nasa.gov/data/update/gistemp/
2003Jan.html
'We can't be sure whether next winter will be warmer or colder than normal or whether it will fall in the middle 40%. However, we can say this: the odds are that it will be warmer than normal. Thanks to all the gases that our cars and factories are pumping into the air, the climate dice are now loaded.
Please see:
http://www.giss.nasa.gov/data/update/gistemp/
2003Jan.html 
