The prediction based off their climate models is that in 50 or 100 years we're doomed. However, it was established long ago that accurately predicting weather even 4 or 5 days in advance is about our limit. The factors involved in the system that creates climate are FAR too numerous for us to realize.
This is evident in the work of Henri Poincaré's 3-body Problem and Meteorologist Edward Lorenz.
Jules Henri Poincaré (29 April 1854 – 17 July 1912) was a French mathematician, theoretical physicist, and a philosopher of science. He is often described as a polymath, and in mathematics as The Last Universalist, since he excelled in all fields of the discipline as it existed during his lifetime.
Henri Poincaré attempted to answer the question of whether the solar system was stable forever, or if some planets would just simply drift off. This required an attempt to solve the celestial 3-body problem.
The 3 Body problem: Given 3 bodies (e.g. Sun, moon, Earth) and their initial positions and velocities, the problem is to determine the motion of the 3 bodies attracting one another according to Newtons law of gravity. Whilst the it sounds quite straightforward, the problem is surprisingly difficult to solve.
Issac Newton had solved the 2-Body problem and a solution was sought for the 3-Body problem and more generally the N-Body problem).
Given the deterministic way of thought, people believed that they could predict into the future provided they have sufficient information. Thus, given sufficient information they could easily solve the 3-Body problem.
In 1887 the King of Sweden and Norway, Oscar II, initiated a mathematical competition to celebrate his 60th Birthday in 1889. Henri Poincaré selected the 3-Body problem (actually, he considered a 9-Body problem: the then known about 8 planets plus the Sun. However, he realised that the minor components of the solar system would produce perturbations on the planets and thus the problem was closer to a 50-Body problem. He immediately saw the difficulty with this and restricted himself to the 3-Body problem.)
What Poincaré found was that when you add just one body to the problem, it becomes dramatically more complex, and extensively harder to predict an outcome given the multitude of unknown factors associated with this extra body. The slightest perturbation in just one of the bodies dramatically affects the whole in unpredictable ways. This is why he changed his work from that of the solar system (nine planets) to just three.
Edward Norton Lorenz (May 23, 1917 - April 16, 2008) was an American mathematician and meteorologist, and a pioneer of chaos theory.
Lorenz was using a simple digital computer, a Royal McBee LGP-30, to run his weather simulation. He wanted to see a sequence of data again and to save time he started the simulation in the middle of its course. He was able to do this by entering a printout of the data corresponding to conditions in the middle of his simulation which he had calculated last time.
To his surprise the weather that the machine began to predict was completely different from the weather calculated before. Lorenz tracked this down to the computer printout. The computer worked with 6-digit precision, but the printout rounded variables off to a 3-digit number, so a value like 0.506127 was printed as 0.506. This difference is tiny and the consensus at the time would have been that it should have had practically no effect. However Lorenz had discovered that small changes in initial conditions produced large changes in the long-term outcome. Lorenz's discovery, which gave its name to Lorenz attractors, proved that meteorology could not reasonably predict weather beyond a weekly period (at most).
Both the three-body problem and the problem Lorenz faced indicate that there is an incredible amount of unpredictability in complex systems. Simply, a light perturbation in a system that affects climate (such as solar radiation, earth's orbit, human influence) will dramatically affect the climatic outcome. This is called sensitive dependence on initial conditions.
To discover every perturbation in each element that makes up the system of climate is impossible.
To know how each of these perturbations affects each other and eventually determines an outcome is inconceivable.
Beyond the scientific quandary of predicting such outcomes lies various political motivations.
As we have seen in the past, the government capitalizes on disasters in order to carry out policy that otherwise would not have been possible.
Before World War 2 America as a whole held isolationist beliefs, they were hesitant to join Europe in fighting the Axis. However, Pearl Harbor changed that.
More recently, the events on 9/11/2001 changed foreign as well as domestic policy in huge ways. We have now been at war for 9 years and our civil liberties have constantly been under pressure.
The government can not only use these events to their advantage after the fact, but create and/or control them as well.
This is called Problem - Reaction - Solution
Create a problem
Solicit a reaction
Offer a solution
I believe they are creating, or at the very least exaggerating a threat of global disaster. They are soliciting a reaction by inundating us with disastrous predictions and social pressure by telling us "the debate is over" and to get in line. The solutions they are offering us though I do not yet know. Many are concerned with a carbon tax and further police state action. If history is any judge, it will involve more restriction on the individual by the state, certainly not the other way around.
Climategate
Stolen emails from the leading source pushing the climate change theory and predictions showed lies and cover up involving the motivation and data backing their climate forecasts.
Rational Physicist, MIT professor and IPCC author Richard Lindzen extrapolates on the issue as a whole
There are enough red flags surrounding this issue that warrant a re-examination of global warming and the motivations behind it's propagation. As Lindzen points out, you shouldn't take it on faith that you're being told the truth. Look beyond media blurbs and sound bites and examine for yourself.