"But even if I accept your argument (which I don't) that it is warmer now than the Medieval Warm Period that doesn't negate the Medieval Warm Period. So are you going to admit that there was a Medieval Warm Period or are you going to continue to be a denier?"

*Look* at the *end of the graph*.

If there even was a warming trend in the MWP, I deny that the peer reviewed science says it was warmer than it is now. You can't just select one study and say "That's the peer reviewed proof!" I don't have time to read through all the studies in that graph, as the GFC has hit our company and I'm currently looking for work. But what I can say is that the trends at the end of the graph need to be expanded and focused on a bit more clearly as it's hard to read.

Other studies as listed by Tim Flannery in Weather Makers show the MWP to be a LOCAL event in Europe that was then extrapolated out to the rest of the world. It's Euro-centric and totally unscientific to just extrapolate out like that. The studies indicate the planet may have actually been COOLER in the Stratosphere resulting in less energy to move the atmosphere around resulting in trapped, patchy local climate conditions which, strangely enough, on this occasion made Europe warmer. (And avoid the Greenland myth, the ice there is hundreds of thousands of years old).

The National Academy of Science for America has debunked the MWP and confirmed the Hockey Stick. Other studies have done the same.

"No longer just a hockey stick, but a whole hockey team". ;-)

http://www.youtube.com/watch?v=vrKfz8NjEzU&feature=channel_page

Anyway, with you as one of the moderators here we at least know why OLO is publishing so many anti-science denial pieces.

GrahamY said "Eclipse now, you asked for peer-reviewed evidence of the MWP and I gave it to you."

...and...

"But even if I accept your argument (which I don't) that it is warmer now than the Medieval Warm Period that doesn't negate the Medieval Warm Period."

The very paper cited ( http://stephenschneider.stanford.edu/Publications/PDF_Papers/MobergEtAl2005.pdf ) clearly illustrates that the MWP was not warmer than today.

From the concluding paragraph of the paper: "We find no evidence for any earlier periods in the last two millennia with warmer conditions than the post-1990 period — in agreement with previous similar studies".

See more discussion of this paper here:
http://www.realclimate.org/index.php/archives/2005/02/moberg-et-al-highly-variable-northern-hemisphere-temperatures/

Graham, you appear to be setting up a straw-man argument - that there was no warming whatsoever, in any region, in medieval times. Is anyone actually trying to say that? There's good evidence that there was a medieval warming period in parts of Europe and parts of North America. The point is that it wasn't as warm then in those regions as now, and global temperatures are certainly higher now than they were then.

You also said "We also know from ice cores that CO2 does not drive temperature significantly because it increases after temperature increase and decreases after temperature decrease."

Incorrect. This is a common misunderstanding of the situation. Actually, increased CO2 was both a result, and a cause, of interglacial warming. Orbital forcings caused the initial small warming, but then after CO2 levels went up it became the major forcing for the rest of the warming, as positive feedbacks came into play to produce a new equilibrium at a higher temperature (and CO2 level). See an introduction to the topic here:
http://skepticalscience.com/co2-lags-temperature.htm

You also said "Now that the Hockey Stick has been completely discredited"...

That, as much as anything else you've written here, demonstrates that you sole source of information on climate science is denialist blogs.

In the real world, the "hockey stick" is widely accepted among climate scientists, and has been comprehensively validated from a wide variety of sources. Try actually reading the MWP articles I linked to earlier.

Eclipse Now, you said there was no peer-reviewed literature that confirmed the Medieval Warm Period, so I provided your with one. Now you say it's not good enough to show a Medieval Warm Period but to prove it was warmer than now, and you use a graph from Wikipedia to "prove" your point. But it doesn't do that because none of the proxies show a temperature greater than today's. The line at the end suggests today is hotter, but it is not a proxy and so doesn't count because you can't splice different types of measure together like that.

Then you suggest that the temperature increase was limited to some parts of Europe. So here are two peer-reviewed references showing the MWP in Peru and New Zealand - different ocean and different hemisphere. Rein B., Lückge, A., Reinhardt, L., Sirocko, F., Wolf, A. and Dullo, W.-C. 2005. Wilson, A.T., Hendy, C.H. and Reynolds, C.P. 1979.

After you've done that please check out the Wegman Inquiry into the Hockey Stick and you'll find that it has been discredited, at the highest level - bad data selection and bad maths.

And I challenge you to find one article on On Line Opinion that is "anit-science". I am very much an enlightenment thinker and I've spent a lot of my career trying to provide some scientific rigour to the study of public opinion and history. That really is a nasty and unwarranted slur.

In fact this whole site is based on a version of the scientific method where advocates for different positions can come and argue their case against one another. You seem to think that your opinion should never be challenged. That is not scientific.

Matt Andrews, I suggest you go and read Wegman too. You might also want to look up the studies I refer to before advancing the canard that the MWP was confined to a small part of Europe. You're the one who appears to be relying on secondary sources provided by partisan websites.

So let's get onto the argument about CO2 and temperature. This graph is in the reference you refer to http://www.skepticalscience.com/images/co2_temp.gif so I'll use it. It doesn't come up to the present judging on the CO2 concentration which tops out around 285 ppm versus the current 385 ppm or thereabouts.

What the graph clearly demonstrates is that CO2 fluctuates markedly with temperature. What it doesn't show is that it follows temperature both on the way up, and the way down. Now, while you might be able to plausibly but innacurately argue that CO2 drives temperature on the way up, you can't do that on the way down. You have to concede that despite it's radiant properties CO2 is over-powered by something on the way down.

If the measures came up to the present with CO2 concentrations above 350 ppm you would also have to concede that CO2 doesn't appear to be having much effect on current temperature.

Interesting to note in terms of the previous argument about the MWP that from this graph it has been warmer than now in each of the last 4 maxima and that the last 10,000 years has been unusually warm in the last 450,000 years. Also that the greatest risk of temperature change is on the downside not the upside.

GrahamY,

I'll try and clarify my terms. I don't believe that today's data confirms a MWP that disrupts the basic shape of the Hockey-Stick graph. There might be a MWP minute mound, but not a mammoth mountain.

So I completey reject your reading of the graph. You stated:

"Eclipse Now you have a graph reading problem. If you actually follow the red line you will find that it is higher at the beginning around 1000 AD than it is when it stops around 2000 AD."

This is not an art interpretation class.

As the "Climate Crock of the week' youtube channel I subscribe to says, "So the denialist bases their case on this report. Let's try something radical and — I don't know — actually READ the report!"

As Matt Andrews kindly showed, the paper your *red line* is based on concludes:

"We find no evidence for any earlier periods in the last two millennia with warmer conditions than the post-1990 period — in agreement with previous similar studies"."
http://stephenschneider.stanford.edu/Publications/PDF_Papers/MobergEtAl2005.pdf

Ooops.

So are you doing science, or artistic interpretation? What about basic **comprehension**?

>> After you've done that please check out the Wegman Inquiry into the Hockey Stick

i did that

>> and you'll find that it has been discredited

no, i found no such thing.

one non-peer-reviewed report on some of the methods of one paper on one approach to the hockey stick does not discredit the hockey stick.

graham, for one who wishes to promote scientific literacy, you seem to understand very little of the scientific method, the scientific community, or how either works. it's almost as if you were an amateur ...