Many of us are blissfully unaware that almost the whole of human history -from the hunters and gatherers to the rise of towns and cities, the development of science and medicine -the whole of our great human pageant- has taken place within an atypical period of fair weather.
For most of our 4.5-billion year history, the typical pattern was for the earth to be hot, sans ice anywhere. The current ice epoch started about 40 million years ago, with at least 17 serious glacial episodes in the last 2.5 million years, which coincides with the rise of homo sapiens, the rise of the Himalayas and the formation of the Isthmus of Panama, disrupting the flows of warming currents between the Atlantic and Pacific.
Before 50 million years ago the planet had no cyclical ice ages. What it did have was a pair of glacial whoppers: one about two billion years ago, followed by a billion years of warmth and another mega ice age called the Cryogenian (you get the picture!) when temperatures plunged 80 degrees Fahrenheit, creating a global Antarctica, dubbed by pundits as "Snowball Earth."
Recent analysis of ice cores from Greenland show that climate change occurs abruptly with temperature swings of up to 15 degrees over a 10-year period dramatically altering the climate rather than gradual change over hundreds of thousands of years. One thing is certain, change is on the way.
At the recent American Association for the Advancement of Science Conference, climatologists described an "intensification of droughts, heatwaves, floods, wildfires and severe storms" as "early warning signs of yet more devastating damage to come". In Great Britain, Stephen Hawking and the Government's chief scientist, Professor Sir David King, said that climate change that it posed a greater threat than , in tune with other experts who describe global warming as a "weapon of mass destruction."
Our period of unusual tranquility known as the Holocene is on the wane. If all our ice sheets melted (and melting they are-in the past 50 years the waters around the West Antarctic ice sheet have warmed 2.5 degrees centigrade) sea levels would rise two hundred feet, drowning the world's coastal cities. Yet another certainty is the complexity of climate change and all its variables from orbit fluctuations known as Milankovitch cycles, to rising carbon dioxide levels, to shifts in tectonic plates, to solar flare cycles. Some believe that global warming might actually trigger the next major ice age.
One thing is certain: it certainly has been nice to come of age in the Holocene.
Image credit: With thanks to ChArLiE 2010(^:*'s Flickr photostream