Since climate change began pushing up average temperatures. See for example: http://www.google.com/hostednews/afp/article/ALeqM5jbK6a-zNlRk3Az-Upzue83KHF5Bw
It's hard to get a good sense of precisely what the probability is, given that I'm not a climate scientist, but 10% sounds about right - perhaps even a little low.
It's not climate science, it's mathematics. The probability of a specific number being the highest in a sequence goes down rapidly as the number of items increases. And it's not like the temperature is doubling every year, either.
As we did last year, use this thread to make predictions for the next year and next decade, with probabilities attached when practical.
Happy New Year, Less Wrong!