According to Wikipedia, the Medieval Warm Period was a time of warm weather around AD 800-1300 during the European Medieval period. Initial research on the MWP and the following Little Ice Age (LIA) was largely done in Europe, where the phenomenon was most obvious and clearly documented. It was initially believed that the temperature changes were global. However, this view has been questioned; the 2001 IPCC report summarises this research, saying
“…current evidence does not support globally synchronous periods of anomalous cold or warmth over this time frame, and the conventional terms of ‘Little Ice Age’ and ‘Medieval Warm Period’ appear to have limited utility in describing trends in hemispheric or global mean temperature changes in past centuries”.
Of course, there’s many researchers, such as Michael Mann and his thoroughly discredited “hockey stick” that try mightily to make the MWP disappear.
News flash to IPCC. Now a scientist has linked the MWP to success of the Inca civilization in the southern hemisphere. It is not going away any time soon, it is spreading.
The new study is called “Putting the Rise of the Inca within a Climatic and Land Management Context” and was prepared by Alex Chepstow-Lusty, an English paleo-biologist working for the French Institute of Andean Studies, in Lima. Link to paper (PDF) is here (h/t to WUWT reader Corey)
Here is the abstract:
The rapid expansion of the Inca from the Cuzco area of highland Peru produced the largest empire in the New World between ca. AD 1400–1532. Although this meteoric rise may in part be due to the adoption of innovative societal strategies, supported by a large labour force and standing army, we argue that this would not have been possible without increased crop productivity, which was linked to more favourable climatic conditions. A multi-proxy, high-resolution 1200-year lake sediment record was analysed at Marcacocha, 12 km north of Ollantaytambo, in the heartland of the Inca Empire. This record reveals a period of sustained aridity that began from AD 880, followed by increased warming from AD 1100 that lasted beyond the arrival of the Spanish in AD 1532. These increasingly warmer conditions allowed the Inca and their predecessors the opportunity to exploit higher altitudes from AD 1150, by constructing agricultural terraces that employed glacial-fed irrigation, in combination with deliberate agroforestry techniques. There may be some important lessons to be learnt today from these strategies for sustainable rural development in the Andes in the light of future climate uncertainty.
Here is a news article about it that talks of the findings. (h/t to WUWT reader “cotwome”) – Anthony
The four centuries coincided directly with the rise of this startling, hyper-productive culture that at its zenith was bigger than the Ming Dynasty China and the Ottoman Empire, the two most powerful contemporaries of the Inca.
“This period of increased temperatures,” the scientists say, “allowed the Inca and their predecessors to expand, from AD 1150 onwards, their agricultural zones by moving up the mountains to build a massive system of terraces fed frequently by glacial water, as well as planting trees to reduce erosion and increase soil fertility.
“They re-created the landscape and produced the huge surpluses of maize, potatoes, quinua and other crops that freed a rapidly growing population to build roads, scores of palaces like Machu Picchu and in particular the development of a large standing army.”
No World Bank, no NGOs.
The new study is called “Putting the Rise of the Inca within a Climatic and Land Management Context” and was prepared by Alex Chepstow-Lusty, an English paleo-biologist working for the French Institute of Andean Studies, in Lima. Alex led a team that includes Brian Bauer, of the University of Illinois, one of today’s top Inca-ologists. The study is being published in Climate of the Past, an online academic journal.
Alex spends a lot of time in Cuzco and he told me the other day that the report “raises the question of whether today’s global warming may be another opportunity for the Andes.”
The core samples from the sediment of the little lake, Marcacocha, in the Patakancha valley above Ollantaytambo, show that there was a major cold drought in the southern Andes beginning in 880 AD lasting for a devastating century-plus through into 1000AD. This cold snap finished off both the Wari and the Tiahuanaco cultures which had between them dominated the southern Andes for more than a millenium.
It was at this same time that the Classic Maya disappeared in Yucatan. It was also a time, on the other side of the Pacific when major migrations from East Asia took place into Polynesia, an indication of a major Niño event; a Niño sees western Pacific currents switch to flow from West to East.
Core samples from glaciers and from the mud beneath lakes in the Andes, the Amazon and elsewhere have built up a history of the world’s climate and the message is crystal clear. It is that changes have taken place in the past, during the six or seven thousand years of our agriculture-based civilizations, that are just as big as the ones we are facing from today’s CO2 warming.
The message may be, too, that climate change is especially forceful in the Andes. Here we are, sandwiched thinly between the world’s biggest ocean and the world’s biggest jungle. The peaks are so high that they have had until just a few years ago deep ice on or near the Equator.
The valleys and surrounding hills have formed the roof of the human world for at least three millennia, according to Alex Chepstow-Lusty’s core samples. Nowhere else do millions of people live at or even near 4,000ms above sea level where it is cold, but getting warmer.
Today’s warming is also following on a colder spell that started, the core samples say, not long after the arrival of the Spaniards in the 16th century.
For instance, the pollen in the cores says that there was maize being grown under the Incas around the lake at 3,300ms a.s.l. Until recently the upper level for maize around the Urubamba valley was 3,000-3,100ms. In the past few years the maize level has moved up and today there is maize being grown again above Marcacocha.
Alex’s records show that hundreds of terraces were being built around the lake between 1100 and 1150 AD -“lots of mud followed by the heavy pollen of maize.”
Enrique Mayer, at Yale, tells me that “the question of the expansion of maize together with the Inca state is now a proven archeological fact, notably in the Mantaro Valley (Tim Earle).
“The question of why terraces are not worked now as intensively as they could has been worked on (Bill Devevan) in the Colca Valley where the terraces are actually in franco retroceso.
“Also, you have John Treacy’s book on Coporaque which is probably the most technically accessible to the argument that terraces are, like flower pots, expensive to maintain.”
There is also, of course, the work of John Earls on the terracing at Moray.
Today there are thousands upon thousands of fine flights of Inca terraces all over the upper ends of the valleys of Central and Southern Peru but few of them are used on a regular basis.
Efforts have been made, among them by Ann Kendall, the English archaeologist, to rescusitate the old irrigation channels and the use of the terraces in the valleys above Machu Picchu. But most have been re-abandoned.
In the same vein the great forests of polylepis, the world’s highest tree, which capture and conserve moisture, have mostly been cut down for firewood.
As they say, you only have to look in the mirror to see where the problem is.