Why do people think the Medieval Warm Period matters?

Question

Let's just assume the Medieval Warm Period (MWP) was as warm as today (though on a global scale, it almost certainly wasn't). Why does that even matter?

The argument is not that today's temperature is a problem, it's that the current rate of warming is a problem. According to the IPCC, the planet is going to warm 1.5-6°C by the year 2100. We're currently warming at a rate of 0.02°C per year.

In short, even if the planet weren't warmer than the MWP, it will be soon, and during the MWP there were extensive droughts characterized as 'megadroughts'.

http://answers.yahoo.com/question/index;_ylt=AvL2fbPQHYxShWu6muFYaEMjzKIX;_ylv=3?qid=20071227162425AAABRtB

So why does it even matter if the planet isn't yet warmer than during the MWP?

Answer 1

Epistemologically speaking, it doesn't matter.  There is no causal relationship between the factors that affected the MWP and present day arguments about climate change.

People think it matters because it is easier to understand casual relationships rather than prove causal ones.  It's easy to understand that it got warmer in the past and that maybe it's getting warmer today for the same reasons.

The shortened version of this is: It doesn't matter.

Answer 2

Use the past to study the future. After a warming period, we enter a cooling period.

Answer 3

Dana,

I think the point many have missed here is not the fact that temperature now is slightly higher or lower than the peak of the MWP, but the cause of that warm period. As you know and have said yourself; the AGW theory is based on the idea that increased CO2 will result in higher global temperature, for reasons we all understand pertaining to the greenhouse effect.

Most AGW doubters will respond to that by rightly saying that the MWP was a pre-industrial time, thus if CO2 is the primary driver of temperature the source of the temperature increase (if it was in fact CO2 driven) during the MWP could not be anthropogenic. But what is germane to this discussion is the fact that the MWP stopped after some point and temperatures plunged into the Little Ice Age. Since humans were clearly not influential in whatever caused this change in climate – both the MWP and the LIA - we cannot really be sure of the mechanism that drives warming or cooling.

I say all that to get to this: no, it does not matter that the current temperature rivals the MWP peak – as you rightly say, it’s not a problem. But there is a problem with radical projections like the one you cite from the IPCC. I know we’ve discussed CO2 sensitivity before, and the IPCC figures seem to agree with current science on the low end, but dramatically exaggerate on the high end. And again, this is allowing the assumption that CO2 drives temperature. Regardless, the problem with the projections is that they rely on dubious computer models – not empirical data.

The 0.02° C per year increase figure also seems high compared to historical values that show only a 0.6° C increase in 100 years, which is only 0.006° C per year – a full order of magnitude less. If it (the 0.02 value) is correct, it seems more like a short term value that would fall more into the “weather” category than the “climate” category. As we all know, looking at only a small segment of the slope of a line graph can be very misleading, and I fear that this is what the 0.02 figure represents – a small sample of the data with a steep slope extrapolated to show a rapid rate of change. Therefore, my conclusion would be to look at the overall picture and disregard (for now) the spikes of temperature – low or high – while we continue to collect data to see if it really represents a valid trend.

Answer 4

They enjoy thowing rocks at the tank because the thud makes them feel like they've accomplished something.

Answer 5

Dana, I'm sure you've noticed by now that the D/s crowd holds up any change in temperature, IN EITHER DIRECTION, EVER, as indisputable proof that Global Warming is a hoax invented by Al Gore.

Answer 6

Yes so what... it also flourished in other places.

Answer 7

http://www.theaustralian.news.com.au/sto...

"Is the Earth stillwarming?"

She ( Jennifer Marohasy, a biologist and senior fellow of Melbourne-based think tank the Institute of Public Affairs ) replied: "No, actually, there has been cooling, if you take 1998 as your point of reference. If you take 2002 as your point of reference, then temperatures have plateaued. This is certainly not what you'd expect if carbon dioxide is driving temperature because carbon dioxide levels have been increasing but temperatures have actually been coming down over the last 10 years."

Duffy: "Is this a matter of any controversy?"

Marohasy: "Actually, no. The head of the IPCC (Intergovernmental Panel on Climate Change) has actually acknowledged it.

Answer 8

Some of us are interested in the truth, not just finding evidence for what we want to believe.  If the medieval warming period was wamer than it is now (as most geologists were saying untill 10 years ago) then we can get some perspective on how fast the Earths climate can change by natural means and whether the recent climate change is unprecedented.  

I don't think you are interested in finding the truth, just information that supports your beliefs.

Answer 9

It doesn't matter in the least.  It's just another illogical red herring some doubters keep raising.

It was probably much warmer during the Cretaceous period and at various other times in the distant past.  So what?  Climate scientists know of many natural events that can cause significant changes in the climate.  But unless the same cause of a past warming event can be shown active now, it's all insignificant for any discussion of the current warming.

Just because a known orbital anomaly caused climate change in the past, doesn't mean it's causing the current one (in fact, we're quite certain it isn't).  Just because massive volcanic activity in the past caused climate change, doesn't mean it's causing the current one (in fact, we have extensive knowledge of the level of volcanic activity and know it's not).  Just because tectonic shifts (new mountain ranges) caused climate change in the past, doesn't mean it's causing the current one (we know it's not).

The people that keep raising this MWP issue, can't seem to understand the very simple fact that multiple things (including humans) can cause changes to our climate.

Edit:

Susan - Your statement: "the MWP was the universally accepted climate history from the time it happened until 1998 when the IPCC adopted Mann's new hockey stick" is indisputably wrong.  Lambs idea of a global MWP were discounted by others (beside Mann) well before 1998.  See:

http://www.geo.umass.edu/faculty/bradley...

http://www.geo.umass.edu/faculty/bradley...

Dr. Lamb himself, in the 2nd edition (1995) of his book "Climate, History and the Modern World" dropped the idea of a global MWP.  The book is available online at google books, where you can read it in it's entirety.

Answer 10

The planet isn't going to continue to warm.  This is an incorrect statement.

Your entire premise is that because this year is warmer than last year, next year will be even warmer.

We can see from NASA's own data that this is not occurring, as the temperatures have been steady to declining over the last 10 years.

To say that temperatures will continue to increase is just guessing.  There is no evidence to say that it will be warmer next year, as we can show by this years record cold temperatures.

Guessing isn't science.

Answer 11

In short, even if the planet weren't warmer than the MWP, it will be soon.

Correction: Wasn't

In short, even if the planet wasn't warmer than the MWP, it will be soon.

Answer 12

According to the National Academy of Sciences, they are confident the last 20 years is warmer than at least the last 400 and possibly longer. And, they say possibly longer, because the further back in time we go with proxy data, uncertainty in the data reconstruction increases.

See pages 4 and 5.

http://dels.nas.edu/dels/rpt_briefs/clim...

Answer 13

If it is not important then they would not want to "get rid of it" as Demming testified before the senate committee under oath.

http://epw.senate.gov/hearing_statements...

It is easy to see why this graph was a problem for those pushing the global warming alarm. If the world could warm so much on such a short time scale as a result of natural causes, surely the 20th century climate change could simply be a natural effect as well. And the present climate change could hardly be considered unusually hazardous if even larger climate changes happened in the recent past, and we are simply fluctuating in the middle of what nature regularly dishes out?

Those wanting to “get rid of” the MWP run into the problem that it shows up strongly in the data. Shortly after Deming’s article appeared, a group led by Shaopeng Huang of the University of Michigan completed a major analysis of over 6,000 borehole records from every continent around the world. Their study went back 20,000 years. The similarity to the IPCC’s 1995 graph is obvious. The world experienced a “warm” interval in the medieval era that dwarfs 20th century changes. The present-day climate appears to be simply a recovery from the cold years of the “Little Ice Age.”

But the real question is if climate scientists so politically motivated that they want to get rid of MWP what other areas are they perverting.

Then you have the wegman report that was highly critical of the way the climate science community operated.  It is like you and your friends here on yahoo answers are the judges as to what is allowed to be posted here and are the peer reviewers.   Bob your question supports the theory, I will say it is based on sound science.  Tomcat I do not agree with your answer, so we are going to block your answer.  The wegman report said the same thing.

In our further exploration of the social

network of authorships in temperature

reconstruction, we found that at least 43

authors have direct ties to Dr. Mann by

virtue of coauthored papers with him. Our

findings from this analysis suggest that

authors in the area of paleoclimate studies

are closely connected and thus

‘independent studies’ may not be as

independent as they might appear on the

surface.

Man study was flawed.  But yet it passed the peer review process.  Why?

The there is also the issue on how readily the hockey stick was accepted.  Any study that supports the AGW hypothesis is accepted without question.   It shows political motivation not scientific ones.

Answer 14

Speaking only for myself...... The 'MWP' provides a possible example of climate extremes occuring without man's influence.  But I have to acknowledge that attempting to piece together the climate during that period sans measuring instruments with any degree of accuracy is suspect.  Much of the data used now to study and forcast Earth's temperature is questionable.... despite claims of adjustments made to correct such faulty data.

The whole issue is credibility.  The AGW cause decided to hastily  plunge head-first into an alarmist strategy and are now suffering the consequences.  The alarmist' science is questionable at best..... the actions taken to date have been laughable....ie. 'ethanol' and mercury-laden fluorescent bulbs.  

I applaud the efforts of the handful of AGW supporters in this forum...... they are.....if nothing else.....blindly loyal!