Is the Sky Falling? (or melting) - Part 3

For now, pending me looking at how they calculate the data, I am assuming the earth has warmed about one degree Celsius over the past 130 years. This brings into play the second group of questions that I developed.

1. What is causing it, and how do we know?
2. What is the timeline of the warming trend? (past/future)
3. How fast is it warming now?

Because I like taking things out of order I will answer the last two first.

What is the timeline?
From the official temperature data we have been in a warming trend for a little over 100 years. Over that time we have  seen the average temperature increase, as I said, about one degree Celsius. If that were to continue based on a linear interpolation we could expect to see it go up another degree over the next 100ish years.

I am not the expert here so I am going to bring in good old NASA. NASA says that according to models we can expect 2-6 additional degrees (C) of warming in the next century. Now, that is a big range, and I can tell you from personal experience in making models that accuracy is... limited. It is reasonable that it doesn't match my linear estimate though

Here is a graph from NASA on a longer term historical temperature history.


Now if you look at that timeline, we are on the tippy top of the far right peak. According to the linked article we are experiencing much more rapid warming than we have seen in previous warm period and they say that is worrisome. I haven't had a chance to really go through all the data, but just looking at that graph it doesn't look any steeper. In fact the warm period just to the left, about 100,000 years ago looks steeper than this period, and certainly hotter. Additionally, the timing of this warming period looks relatively periodic with the last three or four warm spells. I have to get my hands on this data to get a better feel for it. Because just from this and the graph from yesterday it really really looks periodic and normal. I realize there is a certain level of confirmation bias here, but I am not seeing anything that strongly shakes my previous leanings.

What is causing it? and how do we know?
Well the somewhat obvious proposed short answer is greenhouse gasses. Greenhouse gases are gases that absorb solar radiation and therefore contribute to the heat capacity of our atmosphere. The argument goes that the more of these gases we put into our atmosphere the warmer it gets.

The all knowing Wikipedia says that the top four greenhouse gases are (in order of importance):
1. Water vapor and clouds
2. Carbon dioxide
3. Methane
4. Ozone


The how do we know part of the question is a bit of a hang up for me. GPWayne of skepticalscience.com has a very nicely articulated article outlining why global warming is in fact man made. To be fair to everyone involved I am going to devote a whole post to it because it is late and I can't process it in just a couple paragraphs. So if you are on the edge of your seat you can read ahead.