Why do MWP-naysayers believe proxy models that don't pick up post-1990 warming?

Question

Wouldn't that mean that their failure to pick up the Medieval warming doesn't mean that it didn't happen?

http://www.climateaudit.org/?cat=5

Um, right, no, this is THE research and models - Mann's model, the one relied upon by the IPCC, doesn't pick up the post-1990 warming. It's precisely that warming that is supposedly unprecedented, even considering the MWP, to whatever extent the AGW groups wish to acknowledge it (and various groups acknowledge it to varying degrees). And it's the lack of appearance of the MWP in Mann's model that supposedly means the MWP didn't happen or wasn't as significant as was previously thought.

But if the model doesn't pick up today's warming, the fact that it doesn't pick up the MWP is meaningless.

Thus, even if it made sense, which it doesn't, to dismiss the physical evidence from the period (e.g., what grew when and where) and instead rely on the proxy models, the proxy models cannot be relied upon for this purpose.

Night, look, it's real simple - if the model doesn't pick up the present warming, then the fact that it doesn't pick up the Medieval warming doesn't mean the Medieval warming didn't occur - - and the model's failure to pick it up is the sole indicator that it didn't happen, while the physical evidence from the period and the contemporaneous observations that it was happening strongly suggest that it did.

This goes beyond the question of AGW - - - even if you conclude that the present warming is or could be caused entirely or primarily by man, there remains no valid reason to deny that the MWP happened and was exactly what Lamb said it was.

Bob the tangible evidence of the MWP consists of stuff growing where it can't today. Not in one or a few remote corners of the world but around the world. Such evidence taken piece by piece is 'anecdotal' but the sum of all the anecdotes covers almost the entire globe for over 300 years.

The graph you present is NOT the proxy models. It's the proxy models up until 1900 and then it's the measured temps. The proxy models fail to pick up any warming past 1990. That means their failure to pick up warming before 1300 doesn't mean the warming didn't occur.

Once you toss out the proxy models, you have to go back to what grew when and where - which indicates a climate still warmer than today.

Maybe the MWP was natural and this is man-made, but the MWP happened and happened on a similar scope and scale.

That's all this is about - you don't have to disbelieve that the present warming is manmade to admit the MWP was real and as significant as the present warming.

OK so Keith, if as you admit, tree ring data is uncertain, doesn't that throw out the proxy models altogether, which means we have to go back to the so-called 'anecdotal' evidence which actually comes from anecdotes over almost the entire globe for 350 years?

That's all I'm saying - how can we rely on such proxy models and just throw out the evidence of what grew when and where, and what travel routes were ice bound, which is NOT scant, NOT limited to only a handful of examples, NOT a matter only of record but are in fact evidenced physically? In any event even if you still want to go with the proxy models, why don't you feel obligated to explain how these myriad events took place?

If it wasn't warmer, how'd the Vikings do it? And don't give me "well it was warmer only THERE" - THERE's Greenland, which you people said was the canary in the coalmine this go-round - why not last go-round? And it's NOT JUST GREENLAND - as I've shown.

Mann's multi-proxy model is based largely on tree rings and does not pick up the post-1990 warming. It also bases entire centuries on rings from a single tree. Other multi-proxy models using broader sets of data samples DO show the medieval warming.

So there are two questions really:

1) Given that the broader the data set, the more the climate looks like the pre-1998 camel-hump graph and less like the Hockey Stick, why use LESS data?

2) In any event, even if you go with Mann's model over the others, how can we just dismiss out of hand the physical evidence? Do you feel no obligation to explain how the events that since they happened have been attributed to climate happened, if not for climate?

It can't be that they happened because of climate AND that the climate wasn't warmer - we're talking farming with hand tools where there is now permafrost.

Night, is this or is this not a 'free society' - what you consider to be 'us taking real action' is really you forcing everyone else to take actions they don't want to take.

How can you justify this without proof?

OK let's try this again. The physical evidence of warmer climate 1000 years ago is not at all limited to one or a few corners of the world - it's abundant and from all over civilization. What grew when and where, what sea and land-based trade routes weren't iced over that are now, etc... as well as contemporaneous observations that they were able to grow certain crops in certain places where they weren't previously able to because it was warmer.

On that evidence the uniform position of all climatologists prior to the climate becoming a political issue was that there was a period of about 350 years that was 2 degrees C warmer than the middle of the 20th century - which would still be warmer than today.

That would not in and of itself DISPROVE that the present warming is manmade. It would however indicate two things, one, that one can't infer human causation simply from the rough temporal correlation between human CO2 generation and the present warming trend, and two, that since the world didn't fall apart last time, it won't fall apart this time.

In other words, if you're certain of your theory that human-generated CO2 would have effects that will dwarf the effects to date, and that at some point tangible proof of causation would be produced, it should not matter that there have been other warm periods not caused by humans.

But at the time, the temporal correlation is all anyone had, and the skeptics were making a lot of hay out of the known fact that it had been warmer.

The buzz among the AGW movement was "we need to get rid of the Medieval Warm Period." However the UN IPCC reports included the long-established climate history showing two humps with the present hump not yet reaching the levels reached in medieval times.

In 1998 Michael Mann, who was not exactly on the fence about man-made global warming, produced a model which, based on proxy data - primarily tree rings but also ice cores - showed a new "Hockey Stick" climate history.

Only the blade, a long temperature descent from AD 1000 to AD 1900, was based on the model - from 1900 to present, the 'blade' or dramatic increase in temperatures was from measured surface temperatures.

The UN IPCC went with this "Hockey Stock" right off the bat - dropped the long-established climate history that had been based on physical evidence from around the world in favor of the proxy model.

It was later revealed that Mann's proxy model used very narrow sets of data - the rings from a single bristlecone pine tree were used to cover the entire 14th century, for example.

It has since been established that the more data you plug into the model, the more the MWP and LIA show up, though the MWP doesn't rise to the level originally thought.

It has also been shown that when you plug random data into Mann's model, the resulting shape is the downward slope.

Mann has consistently refused to divulge the actual equations used to make the model.

He had for quite some time also refused to update proxy samples, most of which ended in the mid to late 20th century.

But the data that does exist from 1990 on has been plugged into the model, and guess what?

The supposedly 'unprecedented warming' since 1990 is not picked up.

THAT MEANS THAT THE MODEL'S FAILURE TO PICK UP SIMILAR MEDIEVAL WARMING DOESN'T MEAN IT DIDN'T HAPPEN.

And the original question still remains:

How do you just dismiss out of hand what had been the universal concensus on the climate history since it occurred? And how do you explain the myriad events on which that climate history was based?

Even if you still buy Mann's model to mean that it wasn't really warmer then - if it wasn't really warmer then, how do you explain all the examples of wild and domesticated animal and plant species growing and thriving where they don't today? How do you explain the clear record of what water and land routes were iced over and when?

Nobody has ever explained ANY of them.

Mann's website offers only that they now grow wine grapes again in England.

Yeah, after 1,000 years of breeding and improvements to growing techniques.

They don't grow the same grapes in Britain that they grow in Provence using the methods used in 1000 AD.

In 1000 AD, they DID.

How'd they do that if it wasn't warmer?

Answer 1

That title contains too many large words.

Answer 2

Show me a recent proxy model that doesn't pick up the MWP. Bet you can't. Here's a list of some that do:

Briffa, K.R., 2000: Annual climate variability in the Holocene: interpreting the message of ancient trees. Quat. Sci. Rev., 19(1–5), 87–105.
Briffa, K.R., T.J. Osborn, and F.H. Schweingruber, 2004: Large-scale temperature inferences from tree rings: a review. Global Planet. Change, 40(1–2), 11–26.
D’Arrigo, R., R. Wilson, and G. Jacoby, 2006: On the long-term context for late twentieth century warming. J. Geophys. Res., 111(D3).
Esper, J., E.R. Cook, and F.H. Schweingruber, 2002: Low-frequency signals in long tree-ring chronologies for reconstructing past temperature variability. Science, 295(5563), 2250–2253.
Hegerl, G.C., T.J. Crowley, W.T. Hyde, and D.J. Frame, 2006: Climate sensitivity constrained by temperature reconstructions over the past seven centuries. Nature, 440, 1029–1032.
Mann, M.E., R.S. Bradley, and M.K. Hughes, 1999: Northern hemisphere temperatures during the past millennium: Inferences, uncertainties, and limitations. Geophys. Res. Lett., 26(6), 759–762.
Mann, M.E., and P.D. Jones, 2003: Global surface temperatures over the past two millennia. Geophys. Res. Lett., 30(15), 1820.

Proxy climate data is generally given a 30-year filter to avoid confusing a change in the weather with a change in the climate. Thus it is not surprising that we don't have proxy data from less than 15 years ago; the statistical validity cannot be vouched for, and would not be the same as for the rest of the time data series.

Answer 3

I am confused by your question. Not sure what your asking. Your link is for what? I thought maybe it was evidence to show some change in climate but if it is it only would be to one small area. Unless you poked a hole in every tree on earth you could not begin to make a guess at an average of any thing. You also would have to take into account rain fall, humidity and any other thing that affected tree growth. This would also be weak because it leaves out places that have no trees such as the poles, desert areas, and grass lands.

Answer 4

It is human nature to select the data that supports our preconceptions. It's also a classic debating technique.

Most of us--myself included--lack the training to understand the complexities of the global climate, so we have to rely on the scientific assessments that are at our disposal. Mainstream climatologists seem to agree that global warming is occurring and that one factor is human activity, but there is some dissent.

Those with political axes to grind choose the assessments that support their position. I stay out of those arguments, listen, and try to learn.

All of this is part of the larger question humanity's responsibility to refrain from harming the environments in which we live--to make as few messes as we can and to clean up after ourselves as best as we are able.

With buisiness, both of those invole spending money on which no return can be hoped for, so when it is society's interest to make sure these jobs get done, the government has to either regulate the industries or clean up the messes itself.

The first approach angers the business community with its huge resouces for lobbying and campaign contributions and the second one increases our taxes, which angers the voters. Often the politicians take the cowards' way out and simply do nothing at all.

So it is with climate change. It is far easier to latch onto the dissenter's views and minimalize the problem than to take any real action.

Answer 5

For openers, I do believe we are seeing a climate shift, 'kay?
However, I am not certain that there is adequate evidence to confirm that this is shift is the result of human activity, at least the "correctable" human activity.
Forest fires, wars (remember the burning oil fields of Kuwait?), and natural events (vulcanism, the exhalations of oceanic biomass, etc.) may have more to do with the warming trend than the emissions from Joe Average's tailpipe.
This is not to say that we should not be aware and take what steps we can to modulate the climate ... for the practice if nothing else (who knows, we may really need to make corrections).
However, the near-hysteria and the bogeyman news items on this issue are not promoting sound science. Why, one alleged scientist even proposed setting off nukes to create a nuclear-winter effect to offset global warming ... there's a solution for you, huh?
I suspect that the "naysayers" are simply hoping for a more effective, and definitive, approach.

Answer 6

Climate modelling is about making future predictions and this is notoriously difficult, that's why the various reports about what the future holds in store vary so much.

If we take data sets from about 1000 years ago and feed them into a modelling programme it will show the MWP. What couldn't be predicted is the subsequent events that would bring about the end of the MWP and a period of 'global' cooling.

In any event, modelling isn't about proving or disproving the existence or causes of global warming. We've incorrectly predicted future population changes, it doesn't mean we don't exist.

Answer 7

Global warming scientists do believe the MWP, of course. They consider it, just as they consider the sun, etc. It just doesn't resemble the current warming. 10 different peer reviewed studies. The graph cuts off in 2004, if it went to 2006 it would be even more impressive.

http://www.globalwarmingart.com/wiki/Image:1000_Year_Temperature_Comparison_png

Answer 8

Tree-ring data is just one of many components used in a multi-proxy reconstruction of past temperatures, and it's the most uncertain. Several important caveats must be borne in mind when using tree-ring data for palaeoclimate reconstructions.

Not least is the intrinsic sampling bias. Tree-ring information is available only in terrestrial regions, so is not available over substantial regions of the globe, and the climate signals contained in tree-ring density or width data reflect a complex biological response to climate forcing.

Non-climatic growth trends must be removed from the tree-ring chronology, making it difficult to resolve time-scales longer than the lengths of the constituent chronologies.

Furthermore, the biological response to climate forcing may change over time. There is evidence, for example, that high latitude tree-ring density variations have changed in their response to temperature in recent decades, associated with possible non-climatic factors. By contrast, some scientists (Vaganov 1999, below) have presented evidence that such changes may actually be climatic and result from the effects of increasing winter precipitation on the starting date of the growing season.

Carbon dioxide fertilization may also have an influence, particularly on high-elevation drought-sensitive tree species, although attempts have been made to correct for this effect where appropriate.

Thus climate reconstructions based entirely on tree-ring data are susceptible to several sources of contamination or non-stationarity of response. For these reasons, investigators have increasingly found tree-ring data most useful when supplemented by other types of proxy information in “multi-proxy” estimates of past temperature change.

Briffa, K.R., 2000: Annual climate variability in the Holocene: interpreting the message of ancient trees. Quat. Sci. Rev., 19, 87-105.
Briffa, K.R., F.H. Schweingruber, P.D. Jones, T.J. Osborn, S.G. Shiyatov and E.A. Vaganov, 1998: Reduced sensitivity of recent tree-growth to temperature at high northern latitudes. Nature, 391, 678-682.
Crowley, T.J. and T. Lowery, 2000: How warm was the Medieval warm period? Ambio, 29, 51-54.
Jones, P.D., K.R. Briffa, T.P., Barnett and S.F.B. Tett, 1998: High-resolution palaeoclimatic records for the last millennium: interpretation, integration and comparison with General Circulation Model control run temperatures. The Holocene, 8, 455-471.
Mann, M.E., R.S. Bradley and M.K. Hughes, 1998: Global-scale temperature patterns and climate forcing over the past six centuries. Nature, 392, 779-787.
Mann, M.E., R.S. Bradley, and M.K. Hughes, 1999: Northern Hemisphere Temperatures During the Past Millennium: Inferences, Uncertainties, and Limitations. Geophys. Res. Lett., 26, 759-762.
Mann, M.E., R.S. Bradley and M.K. Hughes, 2000: Long-term variability in the El Nino Southern Oscillation and associated teleconnections. In: El Nino and the Southern Oscillation: Multiscale Variability and its Impacts on Natural Ecosystems and Society, H.F. Diaz and V. Markgraf (eds.), Cambridge University Press, Cambridge, UK, 357-412.
Mann, M.E., E. Gille, R.S. Bradley, M.K. Hughes, J.T. Overpeck, F.T. Keimig and W. Gross, 2000: Global temperature patterns in past centuries: An interactive presentation. Earth Interactions, 4/4, 1-29.
Overpeck, J., K. Hughen, D. Hardy, R. Bradley, R. Case, M. Douglas, B. Finney, K. Gajewski, G. Jacoby, A. Jennings, S. Lamoureux, A. Lasca, G. MacDonald, J. Moore, M. Retelle, S. Smith, A. Wolfe and G. Zielinski, 1997: Arctic environmental change of the last four centuries. Science, 278, 1251-1256.
Vaganov, E.A., M.K. Hughes, A.V. Kirdyanov, F.H. Schweingruber and P.P. Silkin, 1999: Influence of snowfall and melt timing on tree growth in subarctic Eurasia. Nature, 400, 149-151.

http://www.grida.no/climate/ipcc_tar/wg1/068.htm
http://www.grida.no/climate/ipcc_tar/wg1/090.htm#2722

Answer 9

I`m sure you have graphs and models that support your view.

give us a link to YOUR research.

And I`ll show you mine.