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On average, about half of the surface of Greenland's ice sheet naturally melts during the summer, and then mostly refreezes with the approach of winter. This year, nearly the entire ice cover, from its thin, low-lying coastal edges to its two-mile-thick center, experienced some melting at its surface, according to measurements from three independent satellites analyzed by NASA and university scientists.
"This summer, we have seen melting at the very highest elevations of the Greenland ice sheet, which we have not seen before in the satellite record," said climatologist Thomas Mote of the University of Georgia, who studies snow cover. Researchers expect much of it to refreeze.
Originally posted by VoidHawk
Originally posted by littled16
I have heard that once upon a time Antarctica was ice free, and that maps have been found to prove it. I myself don't know for sure if they are legitimate or not, but it gives rise to questions of whether or not we may be going through a natural heating cycle.
Piri Reis Map
I think those maps are genuine because when they were discovered(think it was about 1500's) we didn't even know the arctic existed.edit on 22-9-2012 by VoidHawk because: (no reason given)
Originally posted by poet1b
There is nothing natural about this warming cycle. The historical record shows us this has never happened before so rapidly.
We are about to go on one crazy ride.
Originally posted by poet1b
All evidence shows that warm periods in the past lasted for thousands of years. There is no evidence the ocean currents will shut this down.
Originally posted by moniesisfun
I think you need to back up your claims. The science says we have surpassed those events you're mentioning.
Originally posted by poet1b
Ice on Greeland has retreat beyond where it was during the time of the Vikings, within a decade. The historical record shows that we are heating up faster then ever before.
You want to ignore this, it's your choice.
Moreover, the impact of the RWP to the East Asian ancient history is not clear also because there were no notable political factions in all East Asia except in some parts of China.
II.2.3 The Medieval Warm Period
After the DACP was another warm period that continued until c. 1350 A.D., and it was wet and warm again like the RWP. Although some scientists argue that actually there was no significant warm climate during the MWP in East Asia, it seems evident that at least the 12th century was warmer than any other periods - even warmer than today-discussed on this paper. (8)
On-line Publication Documentation System for Stockholm University
Full DescriptionUpdate record
Publication type: Article in journal (Reviewed scientific)
Author: Grudd, H (Department of Physical Geography and Quaternary Geology)
Title: Torneträsk tree-ring width and density ad 500–2004: a test of climatic sensitivity and a new 1500-year reconstruction of north Fennoscandian summers
In: Climate Dynamics
Publisher: Springer, Berlin / Heidelberg
Department: Department of Physical Geography and Quaternary Geology
Language: English [en]
Subject: Physical geography, Climatology
Abstract: This paper presents updated tree-ring width (TRW) and maximum density (MXD) from Torneträsk in northern Sweden, now covering the period ad 500–2004. By including data from relatively young trees for the most recent period, a previously noted decline in recent MXD is eliminated. Non-climatological growth trends in the data are removed using Regional Curve Standardization (RCS), thus producing TRW and MXD chronologies with preserved low-frequency variability. The chronologies are calibrated using local and regional instrumental climate records. A bootstrapped response function analysis using regional climate data shows that tree growth is forced by April–August temperatures and that the regression weights for MXD are much stronger than for TRW. The robustness of the reconstruction equation is verified by independent temperature data and shows that 63–64% of the instrumental inter-annual variation is captured by the tree-ring data. This is a significant improvement compared to previously published reconstructions based on tree-ring data from Torneträsk. A divergence phenomenon around ad 1800, expressed as an increase in TRW that is not paralleled by temperature and MXD, is most likely an effect of major changes in the density of the pine population at this northern tree-line site. The bias introduced by this TRW phenomenon is assessed by producing a summer temperature reconstruction based on MXD exclusively. The new data show generally higher temperature estimates than previous reconstructions based on Torneträsk tree-ring data. The late-twentieth century, however, is not exceptionally warm in the new record: On decadal-to-centennial timescales, periods around ad 750, 1000, 1400, and 1750 were equally warm, or warmer. The 200-year long warm period centered on ad 1000 was significantly warmer than the late-twentieth century (p < 0.05) and is supported by other local and regional paleoclimate data. The new tree-ring evidence from Torneträsk suggests that this “Medieval Warm Period” in northern Fennoscandia was much warmer than previously recognized.
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
P. D. Tyson1, W. Karlén2, K. Holmgren2 and G. A. Heiss3.
1Climatology Research Group, University of the Witwatersrand
2Department of Physical Geography, Stockholm University
3Geomar, Wischhofstr. 1-3, 24148 Kiel, Germany; present address: German Advisory Council on Global Change (WBGU), P.O. Box 120161, 27515 Bremerhaven, Germany, E-mail: email@example.com
The Little Ice Age, from around 1300 to 1800, and medieval warming, from before 1000 to around 1300 in South Africa, are shown to be distinctive features of the regional climate of the last millennium. The proxy climate record has been constituted from oxygen and carbon isotope and colour density data obtained from a well-dated stalagmite derived from Cold Air Cave in the Makapansgat Valley.
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. It was variable throughout the millennium, but considerably more so during the warming of the eleventh to thirteenth centuries. Extreme events in the record show distinct teleconnections with similar events in other parts of the world, in both the northern and southern hemispheres. The lowest temperature events recorded during the Little Ice Age in South Africa are shown to be coeval with the Maunder and Sporer Minima in solar irradiance. The medieval warming is shown to have been coincided with the cosmogenic 10Be and 14C isotopic maxima recorded in tree rings elsewhere in the world during the Medieval Maximum in solar radiation.
Evidence for the existence of the medieval warm period in China
Journal Climatic Change
Publisher Springer Netherlands
ISSN 0165-0009 (Print) 1573-1480 (Online)
Issue Volume 26, Numbers 2-3 / March, 1994
Subject Collection Earth and Environmental Science
SpringerLink Date Monday, February 07, 2005
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Evidence for the existence of the medieval warm period in China
(1) Chinese Academy of Meteorological Sciences, Baishiqiaolu No. 46, 100081 Beijing, 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. A new set of data for the latest snowfall date in Hangzhou from A.D. 1131 to 1264 indicates that this cannot be considered a cold period, as previously believed.
Decline Of Roman And Byzantine Empires 1,400 Years Ago May Have Been Driven By Climate Change
ScienceDaily (Dec. 6, 2008) — The decline of the Roman and Byzantine Empires in the Eastern Mediterranean more than 1,400 years ago may have been driven by unfavorable climate changes.
Based on chemical signatures in a piece of calcite from a cave near Jerusalem, a team of American and Israeli geologists pieced together a detailed record of the area's climate from roughly 200 B.C. to 1100 A.D. Their analysis, to be reported in an upcoming issue of the journal Quaternary Research, reveals increasingly dry weather from 100 A.D. to 700 A.D. that coincided with the fall of both Roman and Byzantine rule in the region.
Late Holocene Environmental and Hydrologic Conditions in Northwestern Florida Derived from Seasonally Resolved Profiles of δ18O and Sr/Ca of Fossil Bivalves.
Elliot, M.; de Menocal, P. B.; Linsley, B. K.; Howe, S. S.; Guilderson, T.; Quitmyer, I. R.
AA(Edinburgh University, Dept. Geology and Geophysics, West Mains Road, Edinburgh, EH9 3JW United Kingdom ; firstname.lastname@example.org), AB(Lamont Doherty Earth Observatory, Route 9W, Palisades, NY 10964 ; email@example.com), AC(University at Albany, 1400 Washington Ave, Albany, NY 12222 ; firstname.lastname@example.org), AD(Laurence Livermore National Laboratory, 7000 East Ave, Livermore, CA 94550 ; email@example.com), AE(Laurence Livermore National Laboratory, 7000 East Ave, Livermore, CA 94550 ; ), AF(Florida Museum of Natural History, Dickinson Hall, Gainesville, FL 32611 ; )
American Geophysical Union, Fall Meeting 2002, abstract #PP72A-0429
3344 Paleoclimatology, 4215 Climate and interannual variability (3309), 4227 Diurnal, seasonal, and annual cycles, 4870 Stable isotopes, 4875 Trace elements
We reconstruct environmental conditions of coastal Northwestern Florida from combined measurements of δ18O and Sr/Ca of fossil marine bivalves deposited in an archeological site during the late Holocene period. We first investigated the environmental controls of seasonally resolved records of δ18O and Sr/Ca of modern Mercenaria mercenaria and Mercenaria campesiensis collected live from five coastal sites along the east coast of North America. Seasonal profiles were obtained by sub-sampling the incremental growth layers of aragonite and were compared with in situ historical records of temperature and salinity. We show that these bivalves precipitate their shell in isotopic equilibrium with the water in which they grew and that the δ18O records are not affected by variations in growth rate. Winter growth appears to be interrupted or strongly reduced below water temperatures ranging from 7 to 18° C, depending on latitude. The annual average δ18O decreases with latitude, reflecting both the parallel trend of freshwater δ18O with latitude over the North American continent and the reduced winter growth rate. The Sr/Ca records of the 5 modern bivalves also exhibit seasonal variations can be correlated to water temperature. However, contrary to corals, the Sr/Ca ratio is considerably lower than the average sea water Sr/Ca composition and is positively correlated to the water temperature. We dated and measured the δ18O and Sr/Ca of 30 fossil M. campesiensis from an archeological site close to Cedar Key, in the Gulf of Mexico. Accelerator Mass Spectrometry 14C dates obtained for each shell show ages which cluster between 1100 to 1400 and 2300 to 2600 14C years BP corresponding approximately to two historical warm periods known as the Medieval Warm Period (~ 1300-900AD) and the Roman Warm Period (~ 250AD-200BC). The average annual and summer Sr/Ca of 4 fossil shells are higher than that of modern bivalves from the same location suggesting that annual coastal water temperatures were 3 to 4° C warmer than today. The bulk δ18O values show a marked trend towards more positive values. 24 fossil shells have bulk δ18O values 0.2permil to 0.7permil more positive than modern bivalves from the same location. These results suggest that the coastal waters off northwest Florida were warmer and less saline compared to today and attest of considerable differences of the regional climate and hydrological balance during the Medieval Warm Period and Roman Warm Period.
Antarctic Science (2003), 15:2:173-173 Cambridge University Press
Copyright © Antarctic Science Ltd 2003
Galactic energy and its role in a changing Earth
ALAN P.M. VAUGHAN
Proposed climate change mechanisms are many and various but generally attributable to our part of the solar system. They usually focus on temperature changes driven either by local processes such as variations in oceanic circulation, or, levels of atmospheric greenhouse gases such as carbon dioxide, or by global processes such as variations in received solar energy linked to changes in the parameters of the Earth's rotation and orbit or solar activity. However, two recent papers have suggested that we may need to look outside the Earth System and even outside our local planetary system for the possible origins of climate change, both on a decadal scale and over longer timescales of hundreds of millions of years. In each case, the galactic cosmic ray flux and its potential effects on cloud formation is considered to be the culprit.
Originally posted by Schkeptick
It's called GREENland because it was Green when it was discovered.