What can Global Warming do?
The above are just the basics. The earth is a complex system so many other changes occur. Alpine regions become isolated from each other, thus certain species become "trapped" on a particular mountain because it is too warm for them to migrate to other mountains. Sea streams become effected, thus leading to greater rainfall in some areas and lesser rainfall in others and as well as increased temperatures in some areas and lesser temperatures in others.
It depends on who you choose to believe. The main body for the science is the IPPC, Which is a political UN body, with very few scientists on-board, what they do however is pay for research by scientists on topics they want answers to. Findings are published very often, and change quickly, so by the time this answer is finished the figures could have changed again. As a result of this fluid reporting, their credibility with governments is not great, and many other bodies with differing views are also in existence, or are being created. The possible effects are now identifed as three main outcomes.
1. Sea Level Variations: These originally were increases (up to 10 metres), (Al Gore used this figure for his "convenient truth" movie, but contrary to what he stated, New Zealand is not being overun by climate refugees. (an aside fact A New Zealand court declined the first climate change refugee application in 2013, on the basis that there was no evidence of land loss due to rising sea levels on his home atol) As frozen water (ice) occupies greater volumes than water in a liquid state, and most water is locked at the poles and in the ocean, not on land) these numbers have been reduced down. Some figures show reductions of up to 4 feet, others increases of up to 2 metres, however the current IPPC values are now an increase of well less than 1 metre (in fact it is measured in inches).
2. Climate Change: Weather patterns would alter, and these could cause increased food production in northern and southern climates, but at the cost of a more arid situation nearer the equator, However, modeling has not matched the trends over the last ten years, The UK for example should be warmer and weather patterns calmer as it was following the last Mini Ice age (a period known as the renaissance) but in fact it has been colder and more extreme. As a result, predictions now only state chage, and not what the change will be, as these predictions are about as accurate as next week's weather forecast. So it would change, but no-one can agree on how it will change. Some predict more hurricanes, other show the numbers are falling off, but some are more severe. Some data shows ocean temperature increase, other data shows it falling. There is very little agreement among climatologists, and even less with paleo-climatologists.
3. Changes to Flora and Fauna. Plants and animals can be very sensitive to climatic changes (see 2 above), or changes to the food chain. Fewer rabbits = fewer predators... etc. If the climate changes, then animals may not be able to adapt, and will die off. (e.g. Mammoth extinction, as grasslands did not recover in the last Ice Age. Ironically, Increased CO2 or increased atmospheric pressure would actually increase plant growth, but temperatures or water table changes may slow it down. So again Predicting what is not done, only that it may change.
As is clearly stated: The earth's systems are incredibly complex, and not one modelled prediction has yet come to pass, This is because there are not yet any models that can account for all of the complexity of such a complex system. This does not means models are not worth trying, only that none are yet good enough to make accurate predictions. The earth will find a new equilibrium (it always has, and always will.) The question is will we like living here in the new equilibrium if Global warming is real, and some of the above predictions occur? To know that we will have to wait and see, or identify what is really happening, and finds ways to negate the effects, and scientifically, we are still in the early stages of this study (prior to the 1980's no-one had even considered greenhouse possibilities seriously).