Subject: Has another ice age started? Is global warming holding it at bay

Has another ice age started? Is global warming  holding it at bay
I read about an ice fair on the river Themes in London a 150 years 
ago, around about the time of the beginning of the industrial 
revolution where lots of CO2 was put into the atmosphere. The river 
was solid ice. 
There has only been more greenhouse gasses put into the air but the 
temprature doesn't seem to have really risen.  Is it an indication
that an Ice Age started quite a while back but has been held off by 
pollution?  Also How long does it take an ice age to start?

Re:Has another ice age started? Is global warming holding it at bay