onlooker wrote:Yes, Tanada, but these were mostly regional changes. The fact is that our ability to do Agriculture consistently for the last 10000 years in many areas,attests to the RELATIVELY stable climate we have enjoyed since
"Since then, the world’s climate has remained remarkably stable – boring, even. The relatively static shorelines have made farming, fishing, towns and cities possible. " Referring to the beginning of the Holocene about 11,700 years ago.
That also is a false statement Onlooker. Look at the climate pattern of ancient civilizations the Miceanae Greeks flourished, then disappeared when the climate changed and were succeeded by the ancient Greeks. In Egypt/Asyria/Mesopotamia civilizations rose and fell over and over as the climate pulsed warmer and friendlier then colder and drier. The same is true of the ancient Persian Empire, and different dynasties in China and India and Sumatra and Central America.
The climate has not, repeat HAS NOT been steady and solid for 11,700 years, about the longest any one period of 'stability' has been was about 900 years and several of the cycles were much shorter than that. This meme of a wonderful stable climate since the dawn of agriculture is nothing but a myth that gets repeated ad nauseum and it really kind of pisses me off. History is my thing but don't take my word for it.
Using Clapp’s historical research as a guide, Blom and his team used the space shuttle Challenger to take images that allowed them to detect ancient tracks in the desert. Some of the roads ran beneath modern sand dunes but all of them converged on a central point: in southern Oman in the Middle East. There, archaeological excavations showed that the team had indeed located a site that matched some descriptions of the legendary Ubar, which it turned out had actually been an important water source and a desert outpost where camel caravans assembled to transport frankincense.
Once surrounded by mighty towers that eventually sunk into the sand, Ubar is just one in a growing list of ancient sites that are emerging with help from satellite imagery. Also known as “remote sensing data”, images taken from high above the surface of the Earth can show subtle signs of long-lost societies that are impossible to see from the ground.
As scientists dig in to these sites, they are turning up evidence that changes in climate – both large and small – are at least partly responsible for the rise and fall of many ancient civilizations. Even though Ubar is now located in one of the driest places on Earth, the region was once much wetter and underground water sources were plentiful. Ubar disappeared when water levels dipped so low that a sinkhole formed and enveloped the outpost.
An Egyptian kingdom, likewise, collapsed during an extended drought 4,200 years ago. Droughts have also been linked to the fall of the Maya around 900 AD and the demise of the spectacular Cambodian city of Angkor in the early 1400s.
It’s not surprising that climate change has doomed so many populations, Blom says. After all, it was when weather patterns finally became predictable about 11,500 years ago that complex civilizations finally formed in the first place. A stable climate ensured that crops would grow year after year, and a reliable source of food freed people to settle down and develop culture.
Since then, many civilizations have blossomed into greatness and subsequently disappeared into rubble. As scientists try to piece together the history of where people lived a long time ago, they are increasingly turning to the most modern of technologies: spacecraft that offer an unprecedented view of Earth from above.
There are a variety of ways to spot long-buried settlements in satellite images. In the search for Ubar, Blom and colleagues used computers to enhance images taken in the visible and infrared wavelengths, as well as with radar, allowing them to peer up to 15 feet beneath the surface of dry sand. As they analyzed the sizes and proportions of dust, rocks and sand grains, they could see the boundaries of ancient roads.
In modern-day Iraq and Syria, Harvard archaeologist Jason Ur and colleagues have used NASA satellite images to identify thousands of possible locations for ancient Mesopotamian cities by looking for patches of lighter, drier soil. Those spots indicate where mud brick structures may have collapsed.
Change or perish
In the case of the Maya and other lost cities in Central and South America, the jungle is quick to grow over ancient buildings and other structures, but scientists look to satellite imagery for slight differences in vegetation patterns. Where once there was development, the soil is stressed enough to support plants that are different from those growing in untouched soils. Seeing those vegetation shifts from above helps archaeologists zero in on where to dig.
“Lowland Amazonia is bigger than the continental United States,” says William Woods, a geographer and archaeologist at the University of Kansas, Lawrence. “The only way of discovering these new things is with remote sensing and on-the-ground truthing [measurement verification].”
As archaeologists continue to turn up ever more signs of collapsed civilizations, they are finding plenty of evidence that climate shifts are at least partly to blame for the decline in many cases. Those links offer the opportunity to protect the future of our own society by learning from the mistakes of our ancestors.
“When we excavate the remains of past civilizations, we very rarely find any evidence that they as a whole society made any attempts to change in the face of a drying climate, a warming atmosphere or other changes”, Ur says. “I view this inflexibility as the real reason for collapse.”
“Today we have an unbelievable ability to learn about our environment and communicate what we learn to all of society,” he adds. “We need to take better advantage of our communication technology advances in the face of a changing climate.”
In the very broadest outline you can say the climate has been 'stable' for the last 12,000 years but that is only in the very fuzzy broad sense that no major continental glaciers are covering North America, Asia and Scandinavian.
In the narrow sense of good agricultural weather the pattern has been fluctuating for the entire 12,000 years. In periods of high rainfall the civilizations have abundant food and flourish. In extended periods of low rainfall civilizations get hungry and crumble.
Oh and the dirty little secret of the whole pattern is, the slightly warmer periods have been wetter and greener while the slightly cooler periods have been drier and browner.