CRUNCH TIME: Part One

THE AVERAGE TEMPERATURE of the Earth has been rising, everyone agrees. Climate science has discovered that this has been going on for the last 25,000 years or so but with a hiccup here and there (for example, the Little Ice Age from 1300 AD to 1800 AD). The big question is, how significant is human activity like our burning fossil fuels in large quantities since the Industrial Revolution began?
Climate science also informs us that the past 15,000 years has been a period of exceptional climate stability, just warm and wet enough to favor the development of agriculture. Prior to this, our human ancestors had to cope with the vicissitudes of two great ice ages. There were not a lot of us back then and it is even possible that the human population was sometimes reduced to thousands. Our effect on climate was virtually nil.
During the ice ages lots of snow and ice covered the poles and extended down to the mid -latitudes. The earth received less heat and tended to stay cold. The regular change in the earth's orbit and in the orientation of the poles resulted in warming and the end of each ice age.
The atmospheric winds and ocean currents adjust the amount of ice around the poles by transferring heat from the hotter equator, the air and sea each doing about half the work. One current in particular, the huge current that contains the Gulf Stream, has attracted attention as it appears to influence the climatic 'flip flops' signs of which are found in the ice and sediment records. Climatologists have nicknamed it 'The Great Conveyor'. It is a massive flow judged to be as much as 100 times that of the Amazon River. Starting at the part we call The Gulf Stream, warm water flows northwards towards Greenland and Labrador becoming saltier and cooler. At the top of the loop, it sinks to the lower depths and turns southwards, eventually entering the southern oceans before moving east past the Antarctic and then up into the north Pacific. The final part of the loop returns westwards along the Equator, around Africa and back up into the Atlantic, warming and becoming more saline. A drop of water, taking this amazing journey, would be in transit for about a thousand years!
Should the Great Conveyor slow or even stall, less heat reaches the northern latitudes. The ice sheet will grow. Instead being warmer and wetter than Canada, making agriculture impossible, Europe would become cold and dry leading to crop failures. This could be the 'Crunch Current".