The Global Adjustment (GA) 2nd estimate from November 2015 was 12.4 cents/kWh and the 1st estimate for December 2015 was 11.4 cents/kWh. This is the second time that the GA rate has been over 10 cents/kWh since it was established in 2005.
IESO has produced a backgrounder http://www.ieso.ca/Documents/Understanding_GA_Jan_2016.pdf describing the components of the GA and the methodology for how the estimates and actual GA rates are calculated.
Specifically referring to the November 2nd estimate and December 1st estimate, it is not uncommon in shoulder seasons to see higher GA costs. Electricity demand in shoulder seasons is typically low as a result of fair temperatures which see heating and cooling loads that are lower than in peak seasons. When demand is low, such as in November, the GA is recovered over a smaller consumption volume and therefore the GA rate tends to be higher. Additionally, the November market price of electricity was the lowest average monthly value (1.03 cents/kWh) since October 2014, which put a higher pressure on the GA rate.