During the medieval time period 1200's-1500's the planet was in the middle of a warm period, even warmer than the present. This was also a time of strong solar activity I.E. sunspots. But then during the 1600's-1800's solar activity decreased significantly to the point where the earth entered what we now call the "Little Ice Age". The temperature is estimated to have dropped around 2-3 degrees celcius worldwide which is very dramatic. This is what scientists call the maunder minimum in terms of the solar cycles if I am correct which came and went with the "Little Ice Age".
Now, after hundreds of years of this cold weather the sun became more active peaking in about the 1930's and the 1990's which are the two hottest decades for the planet. Check out the graph for more:
Ok Darren, whats your point? Well, my point is that solar cycle 24 should have started January of 2007 but so far it's a no go. The longer the gap in between the solar cycles the greater the effect on our global temperatures, I'm talking about global cooling to a level where snow may fall 8 months out of the year for us here in North West Jersey and maybe 7 months for the rest of the area. The graph below shows the (blue) line which is the average of the sun spot cycles during the Little Ice Age, (red) showing the average sun spot cycles of current warming periods, and green which is where we currently are right now.
We are following in the foot steps of the maunder minimum and if we don't start that solar cycle soon, we may be living in climate that is usually found up north. If we don't get the solar cycles started by atleast March of 2009 then I personally feel that global temperatures will drop, and the drop could look something like this chart below:
Graphs from: http://icecap.us/