Som ett komplement till bl.a. mitt inlägg 422 700 år av temperaturdata från Antarktis, Temperaturen för 130 000 år sedan, Temperature data – What it really means. Och GLOBAL TEMPERATURE TRENDS FROM 2500 B.C. TO 2008 A.D, kommer här en bra graf över dessa temperaturdata
”The Big Thaw as the Big Ice Age ended about 18,000 years ago.
Not so long ago, ice sheets covered much of the globe. Places like Chicago were under a vast slab of ice and polar bears roamed where London now lies. The frigid air contained little moisture or carbon dioxide – the moisture was locked up in ice, and the carbon dioxide was dissolved in the cold oceans. Sea levels were so low that there was land bridge between Alaska and Siberia, and nomads could walk from New Guinea to Tasmania. The level of carbon dioxide in the Ice Age atmosphere was less than 200 parts per million parts of air (ppm), the level at which plant growth almost ceases. The air was so dry, so cold and so carbon deficient that few plants grew. It was a cold, white, dry and carbon-starved world. Ancestors of today’s humans eked out a survival as nomadic hunters and gatherers.
Then eighteen thousand years ago the world started warming. Not a bit of coal or oil was being burnt by our ancestors, but global temperature rose rapidly, ice melted, water evaporated and carbon dioxide was slowly expelled from the warming oceans. Carbon dioxide levels in the atmosphere rose from under 200 ppm to over 260 ppm.
Temperatures rose not by fractions of a degree but by between seven and twenty degrees. The ice sheets retreated, glaciers melted and sea levels rose, not by a few centimetres, but by about 130 metres in about 13,000 years (an average rate of about one metre per century). Coral reefs and coastal communities were totally submerged. (Even during this period of rapid thaw and rapid sea level rise, one meter per century would give most people enough warning to wake up and move to higher ground).
By 9000 BP (years before the present), conditions became more stable and global temperatures and sea levels fluctuated at about present levels. Plants grew, animal life revived, coral reefs grew again and it became a warm, green, moist and carbon-rich world.
Geologists refer to this warm time as ”The Holocene Climate Optimum”. Note that this era is called an ”optimum”, not a global warming ”crisis”, but the cold centuries that followed it are called ”The Dark Ages”.
Grafen finns här:
Om ”The Urban Heat Effect” på temperaturdata:
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