climate change: the famous hockey stick

So, more recently we are in a naturally warming or interglacial period. However, climate records show that temperatures and greenhouse gases are increasing significantly more than they have in the past.

I wont go into this graph too much. This is the famous 'hockey stick' graph that has gotten so much recent attention with Climategate. (my advisor's opinion on the matter here). It shows measured temperature changes for the past 2000 years from many different sources. Each color represents a different study. It appears as if global temperatures have increased significantly in recent years. From what I understand, the 'trick' that they spoke of in these emails refers to a statistical method that is used to portray changes in graphed data such as this. It is extremely common to use, and is not in fact used to trick people into believing that climate change is real. However, what is not good practice (and I believe makes any scientist seem suspicious) is not to publish your raw data, or to allow the public access to it online.

Even with these arguments against the scientists who published a few of these papers, it seems pretty irrefutable that something is going on here. There have been many studies independent of Climategate that have made the same claims:

1. Paleoclimate paper by Glen MacDonald:
2. Work by NASA:
3. Collaborative paper published in Science compared to Mann et al's work (study sites shown at top):
(all slides courtesy of Dr. Glen MacDonald)

I'm sorry if this is an overkill of climate change graphs, but I would show more if I could. I just want to say that global climate has been warming. And in recent years (since the industrial revolution) it has been very rapidly warming; certainly more than a natural cycle would cause. This pattern has been found in many different studies, using different proxies and different techniques, in many areas of the world.

Climate models that simply use natural warming cycles as inputs do not yield the warming we have seen and measured (such as in these graphs). What is causing that extra warming? Some argue that solar forcing, or increased volcanic activity is the cause. However, when solar forcing patterns are added to climate models, the yield still does not reach current day warming. This leads many to believe that humans are the cause for the extra warming push.