In order for a true ice age to occur, it is required that temperatures in the summer drop to such low levels that it effectively remains winter all year round. Snow that falls in the winter therefore never does melt, but rather continues to accumulate, and the end result is an 'ice age', and the creation of ice sheets as much as two miles thick, the result of annual accumulation of snow cover over many centuries.

A few hundred years ago a not very well understood climate event took place, typically referred to by the misnomer 'the little ice age.' Because this climate event has been misnamed as 'an ice age', this has led to some rampant speculation on the internet that 'global warming causes an ice age.' This is not true.

According to the Ocean and Climate Change Institute
 http://www.whoi.edu/institutes/occi/currenttopics/abruptclimate_curry_testim.html
"The Little Ice Age... was a five-hundred-year-long period of cold conditions affecting Europe and eastern North America. Contrary to what the name suggests, it did not involve ice-covered continents, as in a "real" ice age. But it did cause enough cooling to disrupt human activities...(It did) cause severe winters on both sides of the Atlantic."
They also point that "many of the models used to study changes in ocean circulation have inadequate representations of ocean processes. The models may also be less sensitive to salinity perturbations than the actual ocean is. As a result, we are not yet in a position to predict these types of ocean circulation changes." However they also point out that a study of ocean sediments does suggest that "The climate history of the earth shows that adding freshwater to the North Atlantic disrupts the ocean circulation in ways that cause regional cooling and alter patterns of rainfall and drought."

Therefore the possibility exists that 'Global Warming', by introducing fresh water into the North Atlantic, could affect the Atlantic Conveyer Belt, an ocean current which transports warm tropical water to the western coast of Europe. The water then sinks to the depths of the ocean as it cools, while the heat is released into the atmosphere, and it is this released heat that is responsible for the moderate winters in Europe as compared to the harsher winters in North America. Therefore, there is a possibility that Global Warming could temporarily create the conditions for much harsher winters, but not an 'ice age'. This is a myth being spread around on the internet caused by the misnaming of the 'little ice age' several hundred years ago, which was not an actual 'ice age' (with glaciers and ice sheets covering continents) but rather a time of particularly harsh winter climates. When summer came the snow melted, and there was no accumulation of vast ice sheets.

Ice Ages follow a pattern which is established by variations in the patterns of the Earth's Orbit around the sun and variations in the earth's tilt and rotation. The Earth does not follow a perfectly circular orbit, but rather it follows an eccentric elliptical orbit, with a cycle of one hundred thousand years. The amount of sun light reaching the earth varies depending on how extreme the distance of the earth is at the maximum of the elliptic as well as the variation of distance during each season. The earth also wobbles as it spins, up to 23.5 degrees, a cycle which takes 41,000 years. This wobble also causes the position of the earth in its elliptical orbit to change, a phenemona known as the precession of equinoxes, which follows a cycle of 23,000 years.

Ice Ages occur when all three of these factors are in favorable alignment resulting in the least amount of summer warmth in the Northern hemisphere when summer occurs at the farthest point in the Earth's elliptical orbit. Summer temperatures therefore plunge to winter like conditions, and snow accumulates from year to year rather than melting. Similarly, the ice age ends when the process is the opposite, resulting in increased summer heat, and summers which take place at the closest point in the elliptical orbit.

Not enough information is available to climate modellers to give a firm prediction of whether or not a period of cold winters will result from global warming processes, which explains why they are always found to be lobbying bodies such as Congress for more research grants. The atmosphere is much better understood than the ocean. You might encounter emphatic statements out on the internet that suggest that it is a definite certainty that there will be another ice age caused by global warming, and this once again is a myth based upon a misunderstanding of both the state of oceanic climate science (it is underfunded, and thus these statements are just the expression of one possibility, typically, you might notice, combined with an appeal for more funding to increase our knowledge, which is then misinterpreted as being statements of exact fact...to make matters worse the term 'little ice age' is a misnomer, and thus once again causes all that speculation out on the internet about coming glaciation and so on, when the worst people could expect would be a particularly nasty winter, since it is not at all probable that summers will become winter due to global warming, thus leading to an ice age, since the process of a true ice age is controlled by rotation, spin, and orbital variations of the earth, and is not driven by any of the factors influenced by global warming processes.

Some links
Signs of Rapid Arctic warming since 2000
Siberian permafrost is melting, leading to the potential release of up to 70 billion tons of methane, a greenhouse gas 20 times more powerful than carbon dioxide. The last time this happened, during the Thermal Maximum, much of the United States was plunged under water (see the graphics on the linked page), and became part of the ocean, and this scenario is much more plausible than the misunderstood scenario being spread around on the internet which suggests that the United States will buried under glaciers due global warming.
 http://www.melbourne.indymedia.org/news/2005/10/96784.php

Arctic ice cap at record low
The melting of Siberia has been taking place over the last three or four years, around the same time that the arctic ice cap has been shrinking at an accelerated rate, leading scientists to lower their estimates of an ice free arctic from the year 2100 to the year 2060 given the accelerated rate of melting taking place since 2000. This can be graphically seen on the video linked to on the page below, where the most rapid shrinkage takes place right near the very end of the video.
 http://www.melbourne.indymedia.org/news/2005/09/96358.php

other climate stories...
 http://www.awitness.org/journal/climate_change_links.html