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Originally posted by Muaddib
I am not the one who keeps proposing that anthropogenic CO2 is the cause of the current warming
And i am not the one claiming that "this time around Climate Change is happening much more rapidly than in the past", or because of mankind's activities these changes are happening faster than ever before, when that is not true....
Originally posted by melatonin
Strawman
A cause of current warming. A significant one.
Originally posted by melatonin
A pair of strawmen.
Current emissions of carbon-based GHGs are faster than during the PETM. Said nothing about than ever before.
Originally posted by Irentat
UFO...
So...do you like the article or not? Are you for or against human-caused global warming?
Originally posted by Muaddib
Strawman, that is your claim and that of some others but experiments don't show what you and some others claim, and the GCMs are not only flawed but have been wrong in their predictions, including predicting what cirrus clouds will do during the current warming event.
Climate Changes in the past have been so abrupt that they happened within a decade, the current Climate Change has been ongoing since at least the early 1600s for most of the world and it is still ongoing, so it is neither the fastest climate change nor the most dramatic.
Originally posted by Muaddib
We know that in the past abrupt Climate Changes have happened in less than a decade....
Originally posted by Essan
How do you know that's the case though?
The people who claim such abrupt climate changes have occurred in the past - such as Richard Alley - are the same people claiming that AGW is real (and contributing to the IPCC 4AR) ..... so why believe them? Or is it a case you believe them except when they tell you something you don't want to believe?
Originally posted by Essan
Anyway, such abrupt climate changes are believed to have had specific sudden and catastrophic causes. Totally different to what is (or isn't) happening today - so it's disingenuous to try and draw comparison. They were also of a cooling, not warming, nature
Originally posted by melatonin
Your moving goalposts now.
Originally posted by melatonin
Never said it was the most dramatic or fastest EVA.
That is just your strawman.
Have fun beating your strawmen
Originally posted by Muaddib
So now it is "moving goalposts" to show that GCMs and the whole AGW claim are flawed and wrong?.....
Anyways... so now you are saying you have never claimed because of human activities the current climate change due to anthropogenic forcing is faster than past climatic changes?.....
Only melatonin would try to deny something he himself has stated but a few pages back, and has been trying to claim for months now....
Originally posted by melatonin
...
Other than that, my main claim was that CO2 does not always lag temperature increases, which I showed about 2 pages back, before we digressed into Chem 101 just for you.
Originally posted by melatonin
It is when that was not what we were talking about.
Originally posted by melatonin
Ever heard of the Gish-gallop? Duane Gish would be proud to see you using his approach so well.
Originally posted by melatonin
I made one claim related to such a thing. That current emisions of GHGs are at a greater rate than during the PETM. Just one. The rest are your strawmen.
Other than that, my main claim was that CO2 does not always lag temperature increases, which I showed about 2 pages back, before we digressed into Chem 101 just for you.
Cheers.
Originally posted by Gonjo
I see our believer is still at it...
That has to be one of the weakest proofs to any claim. Thats like saying "You dont always get drunk when you drink, sometimes youre already drunk when you start drinking, therefor drinking doesnt make you to get drunk but vice versa."
Keep up the amazing work...
Originally posted by Muaddib
Wow, what an analogy... Some people come up with the most non-sensical analogies, and they think that proves anything....
What the heck does "drinking" have to do with CO2?... They are entirely different things...
Originally posted by Muaddib
....No Essan, most if not all of the AGW skeptics have investigated and know that there have been abrupt Climate Changes in the past... It is not a claim from the AGW crowd.
... there have been abrupt Climate Changes which have happened within a decade and were not caused by catasthrophic causes.
Stop trying to claim someone is "disengenious" when you haven't even taken the time to research how fast some of the past warming periods have taken, thats "disengenious"....
Without going back in time too much, just by looking at two of the most recent warming periods in the history of Earth we can see that warming periods have been much faster than the current one we are undergoing, as what happened during the Roman Warm Period, and in the case of the Medieval Warm period we find that it was very similar to the present warming.
The Roman Warm Period (circa 250 B.C. to 400A.D.) was a much faster warm period than the present, lasting since it's start about 150 years or so, and it occurred faster than the Medieval Warm Period also.
Despite the claims of some people, evidence from all over the globe tells us that the Roman Warm Period was a "global event" when temperatures were much higher in most places on Earth than it is now.
Originally posted by melatonin
This is the second time you've done this, Muaddib. You also did it earlier with ignoranceisn'tbliss.
Originally posted by melatonin
We know that CO2 causes warming due to its physical properties, this has been known for over 100 years. So, it's not purely a reliance on a correlational relationship. So, his drink, drunk, and getting mashed argument sorta fails miserably.
Originally posted by Essan
Citations please As far as I know the theory abrupt climate change is primarily based on ice core analysis .... And I happen to know a number of leading climate sceptics, none of whom are ice core or deep seabed core specialists - so I doubt they've done independent investigations.
Originally posted by Essan
Such as?
The last 2 I know of are the 8,200kya event and the YD - both believed caused by a sudden switch off of the THC by a sudden release of meltwaters (although other theories ofr the YD also exist).
Description
The climate record for the past 100,000 years clearly indicates that the climate system has undergone periodic and often extreme shifts, sometimes in as little as a decade or less. The causes of abrupt climate changes have not been clearly established, but the triggering of events is likely to be the result of multiple natural processes.
Abrupt climate changes of the magnitude seen in the past would have far-reaching implications for human society and ecosystems, including major impacts on energy consumption and water supply demands. Could such a change happen again? Are human activities exacerbating the likelihood of abrupt climate change? What are the potential societal consequences of such a change?
Originally posted by Essan
I have though ..... but maybe I've missed some sources?
Originally posted by Essan
How can we see that? Where? These periods are not what I know of as 'abrupt climate change' events - I'd describe them as just cyclical warming phases.
Originally posted by Essan
What data do you base this conclusion on?
Originally posted by Essan
Much higher? Data please? I know many places experienced higher temps during the Holocene Climatic Optimum (c10-6kya) - although it seems not all places at the same time. I'm not aware for evidence of significantly higher temps since.
ABSTRACT: Fifty-seven borehole temperature profiles from across Australia are analysed to reconstruct a ground surface temperature history for the past five centuries. The five-hundred-year reconstruction is characterised by a temperature increase of approximately 0.5 K, with most of the warming occurring in the 19th and 20th centuries. The 17th century was the coolest interval of the five-century reconstruction.
Comparison of the geothermal reconstruction to the Australian annual
surface air temperature time series in their period of overlap shows excellent agreement. The full geothermal reconstruction also agrees well with the low-frequency component of dendroclimatic reconstructions from Tasmania and New Zealand. The warming of Australia over the past five
centuries is only about half that experienced by the continents of the Northern Hemisphere in the same time interval.
Science, Vol 283, Issue 5408, 1712-1714 , 12 March 1999
Ice Core Records of Atmospheric CO2 Around the Last Three Glacial Terminations
Hubertus Fischer, Martin Wahlen, Jesse Smith, Derek Mastroianni, Bruce Deck
Air trapped in bubbles in polar ice cores constitutes an archive for the reconstruction of the global carbon cycle and the relation between greenhouse gases and climate in the past. High-resolution records from Antarctic ice cores show that carbon dioxide concentrations increased by 80 to 100 parts per million by volume 600 ± 400 years after the warming of the last three deglaciations.
Glacial geological evidence for the medieval warm period
Abstract It is hypothesised that the Medieval Warm Period was preceded and followed by periods of moraine deposition associated with glacier expansion. Improvements in the methodology of radiocarbon calibration make it possible to convert radiocarbon ages to calendar dates with greater precision than was previously possible. Dating of organic material closely associated with moraines in many montane regions has reached the point where it is possible to survey available information concerning the timing of the medieval warm period. The results suggest that it was a global event occurring between about 900 and 1250 A.D., possibly interrupted by a minor readvance of ice between about 1050 and 1150 A.D.
Chilean Continental Slope, Southern Chile
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Reference
Lamy, F., Hebbeln, D., Röhl, U. and Wefer, G. 2001. Holocene rainfall variability in southern Chile: a marine record of latitudinal shifts of the Southern Westerlies. Earth and Planetary Science Letters 185: 369-382.
Description
The authors used the iron content from an ocean sediment core taken from the Chilean continental slope (41°S, 74.45°W) as a proxy for historic rainfall in this region during the Holocene. Results indicated several centennial and millennial-scale phases of rainfall throughout this period, including an era of decreased rainfall "coinciding with the Medieval Warm Period," which was followed by an era of increased rainfall during the Little Ice Age. Given these results, they concluded that their data "provide further indications that both the LIA and MWP were global climate events."
Globally synchronous climate change 2800 years ago: Proxy data from peat in South America
Frank M. Chambersa, , , Dmitri Mauquoyb, Sally A. Braina, Maarten Blaauwc and John R.G. Daniella
aCentre for Environmental Change and Quaternary Research, Department of Natural and Social Sciences, University of Gloucestershire, Cheltenham GL50 4AZ, UK
bDepartment of Geography and Environment, University of Aberdeen, Elphinstone Road, Aberdeen AB24 3UF, UK
cCentro de Investigación en Matemáticas, A.P. 402, Guanajuato, Gto., C.P. 36000, Mexico
Received 15 August 2006; revised 27 October 2006; accepted 2 November 2006. Editor: H. Elderfield. Available online 19 December 2006.
Abstract
..................
The data are directly comparable with those in Europe, as they were produced using identical laboratory methods. They show that there was a major climate perturbation at the same time as in northwest European bogs. Its timing, nature and apparent global synchronicity lend support to the notion of solar forcing of past climate change, amplified by oceanic circulation. This finding of a similar response simultaneously in both hemispheres may help validate and improve global climate models. That reduced solar activity might cause a global climatic change suggests that attention be paid also to consideration of any global climate response to increases in solar activity. This has implications for interpreting the relative contribution of climate drivers of recent ‘global warming’.
The five scientists determined that the mean temperature of the Medieval Warm Period in northwest Spain was 1.5°C warmer than it was over the 30 years leading up to the time of their study, and that the mean temperature of the Roman Warm Period was 2°C warmer. Even more impressive was their finding that several decadal-scale intervals during the Roman Warm Period were more than 2.5°C warmer than the 1968-98 period, while an interval in excess of 80 years during the Medieval Warm Period was more than 3°C warmer.
Evidence for the existence of the medieval warm period in China
Abstract The collected documentary records of the cultivation of citrus trees andBoehmeria nivea (a perennial herb) have been used to produce distribution maps of these plants for the eighth, twelfth and thirteenth centuries A.D. The northern boundary of citrus andBoehmeria nivea cultivation in the thirteenth century lay to the north of the modern distribution. During the last 1000 years, the thirteenth-century boundary was the northernmost. This indicates that this was the warmest time in that period. On the basis of knowledge of the climatic conditions required for planting these species, it can be estimated that the annual mean temperature in south Henan Province in the thirteenth century was 0.9–1.0°C higher than at present.
Climatic changes during the past 1300 years as deduced from the sediments of Lake Nakatsuna, central Japan
.......................
The sediment record from AD 900 to 1200 indicates hot summers and warm winters with less snow accumulation, whereas the record from AD 1200 to 1950 is characterized by high variation of temperature, with three cool phases from AD 1300 to 1470, 1700 to 1760, and 1850 to 1950. The warm period from AD 900 to 1200 corresponds well to the Medieval Warm Period, and the second and third cool phases are related to the Little Ice Age.
Accumulation and 18O records for ice cores from Quelccaya ice cap. The period of the Little Ice Age stands out clearly as an interval of colder temperature (lower 18O) and higher accumulation. Such evidence demonstrates the Little Ice Age was a climatic episode of global significance. From World Data Center for Paleoclimatology (educational slide set).
09/2006 - Was the Little Ice Age caused by a minimum in the solar cycle?
The Little Ice Age (LIA), a significate climatic cooling of the Northern Hemisphere between the end of Middle Ages and the 18th century, also ocurred in the tropics, and the more likely cause was a minimum in the solar cycles. This has been confirmed after a joint study by UAB researchers and several American universities.
Climate forced atmospheric CO2 variability in the early Holocene: A stomatal frequency reconstruction
C.A. Jessena, , , M. Rundgrena, S. Björcka and R. Muschelerb
aGeoBiosphere Science Centre, Quaternary Sciences, Lund University, Sölvegatan 12, SE223 62 Lund, Sweden
bNational Center for Atmospheric Research, Climate and Global Dynamics Division, Paleoclimatology, 1850 Table Mesa Drive, Boulder, CO 80305–3000 USA
Received 22 August 2005; accepted 16 November 2006. Available online 30 January 2007.
Abstract
The dynamic climate in the Northern Hemisphere during the early Holocene could be expected to have impacted on the global carbon cycle. Ice core studies however, show little variability in atmospheric CO2. Resolving any possible centennial to decadal CO2 changes is limited by gas diffusion through the firn layer during bubble enclosure. Here we apply the inverse relationship between stomatal index (measured on sub-fossil leaves) and atmospheric CO2 to complement ice core records between 11,230 and 10,330 cal. yr BP. High-resolution sampling and radiocarbon dating of lake sediments from the Faroe Islands reconstruct a distinct CO2 decrease centred on ca. 11,050 cal. yr BP, a consistent and steady decline between ca. 10,900 and 10,600 cal. yr BP and an increased instability after ca. 10,550 cal. yr BP. The earliest decline lasting ca. 150 yr is probably associated with the Preboreal Oscillation, an abrupt climatic cooling affecting much of the Northern Hemisphere a few hundred years after the end of the Younger Dryas. In the absence of known global climatic instability, the decline to ca. 10,600 cal. yr BP is possibly due to expanding vegetation in the Northern Hemisphere. The increasing instability in CO2 after 10,600 cal. yr BP occurs during a period of increasing cooling of surface waters in the North Atlantic and some increased variability in proxy climate indicators in the region.
The reconstructed CO2 changes also show a distinct similarity to indicators of changing solar activity. This may suggest that at least the Northern Hemisphere was particularly sensitive to changes in solar activity during this time and that atmospheric CO2 concentrations fluctuated via rapid responses in climate.
The Mucubají glacial activity in the Venezuelan Andes coincides with other records of Little Ice Age (LIA) glacial advances in S. America. Comparison of modern glacier equilibrium line altitudes (ELAs) in Venezuela with the Mucubaji LIA glacier ELA indicates an ELA depression of at least 300 m. Both a decline in temperature and increase in precipitation are required to explain the ELA depression. The precipitation increase is supported by increased catchment erosion recorded in L. Blanca sediments. Pollen records from two sites in the Venezuelan Andes also indicate wetter and colder conditions during the LIA.
Tree-ring and glacial evidence for the medieval warm epoch and the little ice age in southern South America
A tree-ring reconstruction of summer temperatures from northern Patagonia shows distinct episodes of higher and lower temperature during the last 1000 yr. The first cold interval was from A.D. 900 to 1070, which was followed by a warm period A.D. 1080 to 1250 (approximately coincident with the Medieval Warm Epoch). Afterwards a long, cold-moist interval followed from A.D. 1270 to 1660, peaking around 1340 and 1640 (contemporaneously with early Little Ice Age events in the Northern Hemisphere).
P. D. Tyson, W. Karlén, K. Holmgren and G. A. Heiss (in press) The Little Ice Age and Medieval Warming in South Africa. South African Journal of Science.
The Little Ice Age and Medieval Warming in South Africa
.....
The climate of the interior of South Africa was around 1oC cooler in the Little Ice Age and may have been over 3°C higher than at present during the extremes of the medieval warm period.
A team of scientist from Austria and Germany located three stalagmites in the Spannagel Cave located around 2,500 m above sea level at the end of the Tux Valley in Tyrol (Austria) close to the Hintertux glacier. The temperature of the cave stays near freezing and the relative humidity in the cave is always at or near 100%. The stalagmites grew at a rate between 17 and 75 millionths of a meter per year and are nearly 10,000 years old.
...............
The stalagmite is screaming to us that many periods in the past 9,000 years were warmer than present-day conditions!
“If you look back far enough, we have a bunch of data that show that warming has gone on from the 1600s with an almost linear increase to the present,” Akasofu said. He showed ice core data from the Russian Arctic that shows warming starting from the early 1700s, temperature records from England showing the same trend back to 1660, and ice breakup dates at Tallinn, Estonia, that show a general warming since the year 1500.
Akasofu said scientists who support the manmade greenhouse gas theory disregard information from centuries ago when exploring the issue of global warming. Satellite images of sea ice in the Arctic Ocean have only been available in the satellite era since the 1960s and 1970s.