Global Warming

A "heated" debate exists over the topic of global warming on our tiny little planet. Very recently ABC hosted a poll on Facebook concerning global warming and if it is a "proven phenomenon."

The ultimate question that needs to be answered in this debate is:
"Is it a proven phenomenon that humankind is contributing enough chemicals to the atmosphere to individually (as a species) cause a climate shift which will greatly and negatively affect life on earth in the future?"

In order to answer these questions there are many smaller questions that arise where evidence is shown but proof is lacking.

Is the earth getting warmer?
I feel this is a pretty simple question. Over the past few (approximately 7) years, the Earth as recorded by thermometers worldwide has shown an average temperature around .1-.2 degrees warmer than previous years. We don't know that the Earth is continually getting warmer, but I will say that evidence would indicate at least a short term trend. To know how long this trend will last though, we need to examine other factors.

What is the cause of global warming?
Is it carbon dioxide? A sun more active than in the past 8000 years? A decrease in the number of pirates? or is global warming simply due to the earth's natural climate changes? There have been tons of theories proposed and evidence can point to each individual one, but pinning down which is the true cause (or combination of causes) is the mystery we should try to solve.

Are humans to blame for global warming?
Of the above causes of global warming, only an increase in carbon dioxide could potentially put humans to blame. (Ok, so a decrease in pirates could too but that was meant strictly as a joke). It is true that carbon dioxide absorbs heat and will aid in keeping some additional energy in the atmosphere, but at the same time, water vapor is a known greenhouse gas and does the same thing to a much greater degree! The major known components and their effect can be summarized here. Additionally, it is not known the proportion of heat this contributes overall. What part does our sun and it's solar cycles play? What part do naturally occurring phenomena play? What part do the Earth's natural cycles play? I won't disagree with humans contributing to global warming, but I will disagree with quantifications and statements saying we are and aren't "to blame."

Will global warming have catastrophic repercussions in the future?
This is what I hear most and this is the one thing I agree with least. I have heard everything from killer hurricanes, to flooding, to droughts, to economic disaster, to security concerns. I hear the word 'Katrina' a lot when discussing global warming but I would like to point out that circumstantial evidence can only go so far, after all major hurricanes on average have to happen sometime. Katrina was a tragedy, but there were a number of things that went wrong (pumps shutting down, government response, compound damage from hurricane Rita) which raised the damage toll to a staggering amount. Someone may also argue that 2005 was hands down the most active season on record. I would give this argument much more credit, but I would also point out that hurricane seasons from 1997-2007 with the exception of 2005 have been frighteningly average. In addition, what effect does global warming play versus earth's natural 'el nino,' 'la nina' cycles?
I have also heard people talk about the sea level rising and displacing people due to melting ice caps. Additionally, I have been presented with an image of what the world would look like under these circumstances. This image is probably the scariest I've seen. Florida is gone, decent chunks of the Medeterainian and Europe are gone, and large dents are taken out of South America and Africa. If this rise were to happen tomorrow, or next week, or over 100 years it would be a complete tragedy, so we must look into the time frame this worst-case scenario will happen in.
Over the past 100 years, the sea level has risen around 20cm. If we average this out we can see the sea will rise on the order of .2mm/year. Just for argument's sake we'll get absolutely crazy and quintuple that amount! Our seas are rising at an unprecedented 1mm/year now! Let's say the useful life of a building is 500 years (which is also giving about 3-10 times more credit than what is due.) Let us then say this building is on the coast about 5 meters above sea level (most large scale buildings are built at least 10m above for hurricane and coastal flooding safety but we'll ignore that.) During the useful life of the building as stated, the sea level will rise about half of a meter (500 years * 1mm/year) and this is even with a gross exaggeration of sea level change and the building's life span. While there is a very slightly improved chance that the building will be lost during an ocean-related disaster, more than likely, this building will be torn down at the end of its life span and the land will be deemed unfit to rebuild on. Yes, people will be displaced, but it will not occur in a catastrophic manner.
Lastly, I have heard that ecosystems will be damaged such as the polar bear's habitat! I agree that species like the polar bear will have nowhere to live if the arctic does get above certain temperatures and there will be some species that cannot adapt which is tragic. In contrast though I would like to point out that for every polar-dweller that is loosing habitat, there will be hundreds if not thousands of species that gain potential habitat ground. Most of the world's species (including humans) exist on or near the equator. Increasing the temperature would potentially increase the land area which is habitable for such species. Additionally, I feel that adaptation is vastly understated. I agree that there will be some parts of ecosystems that will probably be lost, but one should keep in mind a climate change of 10 degrees will probably take around 2000 years to occur in the worst case scenario (i.e. if the earth constantly continues to get warmer faster than the rate it is already with no cooling trends within that time period.) Mobile species will have no problem (birds will migrate to different areas, animals will travel to where they are more comfortable, etc.) and even in the case of trees, many have seeds that can travel great distances (by wind, animal, water, etc). Additionally trees at the cool end of their "prime" area for growing will become more prominent and fertile and spread further into the formerly cooler regions. One could even go as far as saying a small amount of evolution could occur in that time frame (plants and animals more capable to survive additional heat will do so and spread that ability) although this will probably be a small degree.

I don't want to be misinterpreted so I should point out that I feel it is good to do things which will cut down on CO2 while we figure out more definite answers to the above questions. I will say though, that when it comes to global warming there are simple answers:

Is the earth getting warmer? - Most likely.
Is CO2 to blame for global warming? - At least in part.
Is it a substantial enough part to justify worrying about? - We don't know.
Are humans to blame? - We simply don't know, we should take some precautions against potential causes of global warming, but more than anything more research should be done
Is global warming 'proven' - Plain and simply: no

Additional reading:
Carbon Dioxide and Global Change: Separating Scientific Fact from Personal Opinion

Understanding and Attributing Climate Change

A guide to facts and fictions about climate change

Influence of Cosmic Rays on Earth's Climate

Climate change and solar variability: What's new under the sun?

Earth’s Annual Global Mean Energy Budget