Climate catastrophe in just 6 months
November 17th, 2009Six months is all it took to flip Europe’s climate from warm and sunny into a deep freeze 12,800 years ago. The subsequent mini-ice age lasted for 1,300 years.
The findings are from a study by William Patterson, a geological sciences professor at the University of Saskatchewan in Saskatoon, Canada, published in the journal Micropaleontology.
Patterson’s research is based on mud deposits from Lough Monreagh, a lake in western Ireland, a region he says has “the best mud in the world in scientific terms”. He used a precision robotic scalpel to scrape off layers of mud just 0.5mm thick. Each layer represented three months of sediment deposition, so variations between them could be used to measure changes in temperature over very short periods. Patterson found that temperatures had plummeted, with the lake’s plants and animals rapidly dying over just a few months.
Patterson speculates the most likely trigger for the event was the sudden emptying of Lake Agassiz, an inland sea that once covered a huge swathe of northern Canada. Its sudden bursting poured freezing freshwater into the North Atlantic and Arctic oceans, disrupting the Gulf Stream, whose flows depend on variations in temperature and salinity and causing a global sea level rise of about one meter.
Others have suggested that this event may be the basis for the various flood myths of prehistoric cultures, including the Biblical flood.
Scientists have discovered that the last 10,000 years or so of climate stability – during which time human civilization has developed – is an anomaly. From 65,000 to 10,000 years ago there were periods of abrupt warming and cooling roughly every 1,500 years, when the temperature in Greenland might fall or rise by 10C in a decade. Earth’s climate is normally unstable. So what accounts for climate stability over the period in which human civilization arose?
Chris Stringer, professor of human origins at the Natural History Museum in London, offers an explanation:
Some researchers have suggested this may be linked to the activities of early humans, who started growing crops and clearing forests 8,000 years ago.That may have put enough greenhouse gases into the air to stave off another ice age, but the problem now is that we have gone too far the other way.
The amount of greenhouse gases in the air is greater than at any time in the last million years, so ironically, the threat now is from global warming.