Even the NSIDC data only goes back 30 years which does not represent ice sheet changes affected by climate but rather by weather. Although I suppose it is a moot point as we both seem to agree on the third point.

On the second point, I didn't intend to imply that increasing ice sheets confirmed warmer weather, just pointing out that ice growth doesn't necessarily mean cooling temperatures (that point wasn't really addressed to you).

Essentially yes. It's obviously a slightly simplied view as not all ice sheets behave the same and there are so many external factors influencing them. There are a few studies which suggest that the Greenland and Antartic ice sheets are responding over a period of years rather than centuries to current warming (whether that be atmospheric or oceanic) but even they admit that this could be a short term effect that will soon balance out (i.e they have no idea as they are operating on too short a time scale).

The paper is Bamber et al (2007), Rapid response of modern day ice sheets to external forcing, Earth and Planetary Science Letters; 257; 1-2

On the first point: If your point was more on the lack of direct oberservations of truly longterm trends than an objection to the format of the data then we agree fully.

On the second point, I just want to say I was trying to clarify a bit - in hindsight I got your point the first time, I just wanted to be sure we were on the same page in regards to the implications.  Hopefully that makes some amount of sense - if not just disregard my last reply as I believe we see eye to eye here as well.

I might be off base here (megaman will have to confirm), but I believe he was "angry" about my comments not yours. 

That was largely the point I was trying to make on the first issue and I think we are agreement on the second point also.

I am interested in your opinion on another point though. When we were discussing the Vostok Ice Core data earlier, I think we were largely agreed that it was an initial increase in temperature (due to orbital changes) which likely acted as a mechanism for increasing atmosphoric CO2 (through warming of the oceans). However, I raised the issue that the temperature and CO2 continued to increase (over ~10k years) and suggested that CO2 may have created a feedback which further increased temperatures. If was true then it implies that human emissions will increase the Earth's temperature. I'm not saying that I definately believe this to be the case (and as usual there are many factors at play), only that it is a possibilty and was curious as to your opinion on that point?

The proposition that earth orbit could have a catalyst effect like what you're talking about seems plausible enough in principle, but whether the C02 released as a result was responsible for continued warming is something specific period data would be needed to evaluate.  And I don't mind saying I'm not familiar with this specific phenomenon you're talking about.

The key issues I would look for is how much of the temperature increase cannot be explained by the catalyst effect itself. This would include looking for what impacts it might have, for instance the orbit is eccentric and so is bound to have an effect on the annual heat retention profile of the globe (ie changes in how much heat is retained from year to year) and that alone could compound in either direction.  I say either direction because while a more eccentric orbit would give us periods of increased exposure during periapsis it would also mean periods of decreased exposure during apoapsis.  And I have no problem admitting I've not studied what kind of effect that dynamic would have on our climate.

With that said, if you have any papers on it I'd love to read them, I've alrady added the Bamber et al paper you refered to to my list =P  If this was in fact a greenhouse effect driving climate it is certainly worth studying as an invaluable comparative source for use in studying our current situation - that possibility alone is intriguing.

The orbital variations (Milankovitch cycles) are very interesting as they largely explain the Earth's climate over the past 1 million years and I would definately recommend reading about them as you cleary have a strong interest in the subject. In case you're not familiar with the Vostok Ice Core, here is the data from wikipedia (and as it appears in published journals).

As you can see, the ice ages follow a cycle of ~100,000 years, although I made an error in my previous post as it is orbital inclination that occurs over a 100k year cycle, not eccentricity. There are other, smaller orbital cycles which also affect the climate over ~23k and 41k years. This would suggest that this orbital change may be the initial forcing factor in climate warming. The problem is that inclination is a relatively weak orbital forcing factor and so this is why some scientists suspect that it may create an initial increase in temperature but that this effect must then be magnified by other factors. These other factors are usually thought to be the greenhouse effect (as CO2 can be seen to continually increase with temperature from the data) and ice sheet response. Therefore, if the greenhouse effect is accurate it may present problems in the future as current CO2 levels are ~370ppm (higher than anytime in the past 500k years).

The paper below provides a very good overview on all the information on Milankovitch Cycles and the potential impact they have on climate coupled with possible feedback effects. It also estimates that the greenhouse effect had a ~50% effect on the temperature at the end of each ice age (i.e was responsible for 3-4 degrees warming). It's a liitle old now but it's a good summary and I'd be happy to try and find something more current if you're interested (all the recent papers I have are print outs and I don't have them with me).

Lorius et al (1992), Glacials-interglacials in Vostok: climate and greenhouse gases, Global and Planetary Change, 7;131-143.

(If you have any trouble finding it, I will be happy to send you a link)

atleast some of the action to tackle climate change makes sense from another perspective anyway is what im gonna point out. what do i mean? replacing fossil fuels makes sense anyway, the fossil fuels will run out, climate change or no...so its only logical to adopt alternative forms of energy, is it not?

essentially, if you dont belive in climate change, one can say, in the case of energy, theyre doing the right thing anyway...just for the wrong reasons from your perspectives.

Agreed.

Aah ok, I see what you meant now - I was aware that axial patterns played a role in the transition from glacial to interglacial periods and back and I've look at those transitions to a limited degree (especially the 3 most recent periods), just not in that context of orbital and axial rotational patterns - either way I missunderstood what you were saying initially.

As for Vostok, I'm fairly familiar with it - it was the focus of AGW debate about 2 or 3 years ago when I was first getting involved in the topic. In fact the graph you link above is one of the reasons I believe we are at a much greater risk of catastrophic cooling than we are catastrophic warming - this because I personally have not seen anything to indicate we are going to or even could break the ice age trend with our emissions as it is a boldly pronounced trend in the data.

With that said, I would be fairly skeptical that our ~100ppm influence was capable of being the "last straw" during a peak of this effect due to C02's logarathmic effect on temperature.  Whats more I'm curious as to why 1,000s of ppm have been recorded in our atmosphere during every past geological period starting over 600 million years ago but the temperature that would be associated with those C02 levels by the current greenhouse theory are not found.  This indicates to me that we have either missunderstood the feedbacks, are unaware of a strong negative feedback triggered by high temperatures or rapidly increasing temperatures, that we don't understand the greenhouse effect completely, or a combination therein.