Skip to comments.Michael Mann says climate models cannot explain the Medieval Warming Period – Nor... the present....
Posted on 04/11/2013 3:00:47 PM PDT by Ernest_at_the_Beach
Ice core data shows CO2 levels changed less than 10 parts per million from 1600-1800 during the MWP.
From the Hockey Schtick: A new paper from Schurer et al (with Mann as co-author) finds that climate models cannot explain the warm conditions around 1000 [years before the present, during the Medieval Warming Period] seen in some [temperature] reconstructions.
According to Schurer et al, We find variations in solar output and explosive volcanism to be the main drivers of climate change from 1400-1900. They also claim, but for the first time we are also able to detect a significant contribution from greenhouse gas variations to the cold conditions during 1600-1800. This claim is highly unlikely given that ice cores show CO2 levels only changed by less than 10 ppm from 1600-1800, and the effect of 10 ppm CO2 on the climate today remains undetectable even with modern instrumentation.
Separating forced from chaotic climate variability over the past millennium
Andrew Schurer,1 Gabriele Hegerl,1 Michael E. Mann,2 Simon F. B. Tett,1 and Steven J. Phipps3
Journal of Climate 2013 doi: http://dx.doi.org/10.1175/JCLI-D-12-00826.1
Reconstructions of past climate show notable temperature variability over the past millennium, with relatively warm conditions during the Medieval Climate Anomaly (MCA) and a relatively cold Little Ice Age (LIA). We use multi-model simulations of the past millennium together with a wide range of reconstructions of Northern Hemispheric mean annual temperature to separate climate variability from 850 to 1950CE into components attributable to external forcing and internal climate variability. We find that external forcing contributed significantly to long-term temperature variations irrespective of the proxy reconstruction, particularly from 1400 onwards. Over the MCA alone, however, the effect of forcing is only detectable in about half of the reconstructions considered, and the response to forcing in the models cannot explain the warm conditions around 1000 [years before the present] seen in some reconstructions. We use the residual from the detection analysis to estimate internal variability independent from climate modelling and find that the recent observed 50-year and 100-year hemispheric temperature trends are substantially larger than any of the internally-generated trends even using the large residuals over the MCA. We find variations in solar output and explosive volcanism to be the main drivers of climate change from 1400-1900, but for the first time we are also able to detect a significant contribution from greenhouse gas variations to the cold conditions during 1600-1800. The proxy reconstructions tend to show a smaller forced response than is simulated by the models. We show that this discrepancy is likely to be, at least partly, associated with the difference in the response to large volcanic eruptions between reconstructions and model simulations.
Heck, the climate models cant even explain the present, let alone the past, so this really isnt a surprise:
Michael Mann says climate models cannot explain the Medieval Warming Period I say they cant even explain the present
If the model doesn’t match historic data it cannot be indicative of future trends. If the model cannot be confirmed then it should be discarded.
More climate change horse manure; this whole scientific boondoggle is becoming the unemployable scientist’s way of hitting up the government for a yearly income.
We’d be far better off if the government just paid these idiots a check to STFU.
Michael Mann has lost credibility on this subject going back to the emails of 2010.
Now to some useful facts:
OF THE SUN
When examining the long-term direct record of sunspot observations, it is immediately apparent that the length and amplitude of the 11-year sunspot cycle is not constant. The figure at right shows the yearly sunspot number over the past 380 years. At the beginning of this record, it appears that the sunspot cycle apparently ceased for almost 70 years. One simple explanation would be that there simply were no observations during that time. Another would be that astronomers of that time period were simply not very good at observing, or did not make accurate records of the sunspot number.
However, neither of these explanations are true. First of all, some of the astronomers of that time period were Galileo, Scheiner, Hevelius, Halley, and Herschel. Their observations of other celestial bodies show their prowess; incompetence simply was not the issue. There is no reason to believe that they ignored the Sun. Several reports of sunspots during this time period actually made note of the fact that their seeing a sunspot was considered out of the ordinary for that time period.
Therefore, we are forced to conclude that the Sun does experience occasional lulls in its activity. Using other proxies of long-term activity, such as the 14C abundance, we can see that the Sun goes into these quiescent periods every few centuries. At present we seem to be experiencing the opposite phenomenon; the most recent four cycles are among the most active ever recorded.
Understanding what causes the 11-year sunspot cycle has eluded scientists for centuries, so it goes without saying that we don't understand why it should vary as much as it does, let alone almost vanish completely from time to time. The 30-year record of activity for sun-like stars compiled by the HK Project is just beginning to investigate this phenomenon.
A survey of stars close to the Sun in mass and activity shows the distribution at left. The arrows above the distribution show the range of activity seen by the Sun from the expected activity level in the Maunder Minimum to sunspot maximum, with the line left of center indicating the activity at sunspot minimum. From this, it appears that as many as 25% of the stars surveyed could be in a Maunder Minimum-like state. Therefore, the Sun might spend up to 25% of its time at present under similar conditions.
This figure on the right, shows a similar distribution of activity for two open clusters, Messier 67, which is nearly the same age as the Sun, and NGC 752 which is about 2 billion years younger than the Sun. The arrow above the M67 histogram has the same meaning as in the previous plot. Using open clusters to test the frequency of Maunder minima is preferred because it can be assumed that the age of all the stars in the cluster is nearly equal. Therefore, the distribution observed is more likely to be accurate than using field stars whose ages are not well-known. The distribution for M67 is similar to the field star distribution, and about 1/4 of the stars have low activity similar to the Maunder Minimum. In comparison, the younger open cluster of NGC 752 have very few inactive stars, but the fact that there is a few suggests that Maunder minimum episodes could occur, but a lower frequency than that of stars closer in age to the Sun.
At the same time, a few of the stars which have been observed since 1966 are beginning to show long-term behavior. In the left panel of the above figure, two stars with similar mass and rotation period are shown. Because their mass and rotation are similar, they should have nearly the same level of activity. However, the activity of 54 Piscium (HD 3651) has been decreasing steadily since before 1966. The most recent activity maximum is as low as the activity minimum seen in the early 1970's. This star could be entering a Maunder minimum. On the right is HD 9562, a star close to the Sun in mass. It's activity has only a very small increasing trend over 30 years. From its spectrum, the rotation period must be less than 25 days (i.e., close to the Sun's) but its activity it much lower than the Sun's. Therefore, it is very likely that this star is currently in a Maunder Minimum.
Continued observations of all of these stars will hopefully provide clues as to what the Sun's behavior will be over the coming centuries. An important effect of this research is the investigation of how long-term variations of solar activity like the Maunder Minimum affect the Earth. The time period of the Maunder Minimum also corresponds to a period called the ``Little Ice Age'', when summers in Europe were short and winters were severe. Therefore, further analysis of extra-cyclic stellar activity could provide important clues to a better understanding of changes in the Sun and their impact on the Earth's climate.
Climate models are stupid
the idea of government policy based on them is appalling
It does explain agenda-driven science though. lol
Die Welt vor einer Eiszeit “The World on the Verge of an Ice Age”: Global Warming is nothing more than a marketing trick’
The old perpetrators of orthodoxy and “consensus” are now the new “deniers” scrapping to repeat and salvage summary opinions of current conditions even though their own new research fails to confirm the models they use for those opinions.
The truth - “climate science” is still in preschool, in terms of truly understanding the massive dynamics of how it works sufficiently to predict the end points of the climate’s very long term trends and cycles.
The masses of money they hope to siphon from the private economy over CO2 would be best spent instead left in the private economy on the technologies we will use to ADJUST to climate change; to live with it and to ameliorate the affects of it as needed.
Gee; isn’t that one of the things humaity has always done with its technology, when and how it has found it necessary and possible to do so. By golly it is!!!
The policies ...or Agenda ....if you will...was established first....
The models are to lend the appearance of scientific logic to what the policy want....
That is not the way the Climate Scientists in support of the IPCC are working!
Actually, that Mann has finally admitted that there might have been a Medieval Warm Period is progress for him.
Professing to be wise, they became fools.
|GGG managers are SunkenCiv, StayAt HomeMother & Ernest_at_the_Beach|
It's official: Mann Made Global Warming has disappeared.
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