Abrupt Climate Change and Mass-Extinctions: 5 down, 1 to go?

The End-Permian Event (1), 251 million years ago saw the extinction of 95% of species after runaway global warming was caused by an abrupt 6°C global warming. The Paleocene-Eocene Thermal Maximum (PETM) was an era 55 million years ago when average air temperatures rose as much as 6°C over 20,000 years causing further mass-extinction. After the 5 major species mass-extinctions, a new extreme event could be forming. Several theories have been proposed to explain each mass-extinction from asteroid impact, abrupt sea level change or huge volcanic eruptions. These have all been linked to either a cause or an effect of a abrupt climate change event (See Norman MacLeod's Extinction! review).

However, the 21st century has a new asteroid, a new volcano, known as anthropogenic warming. 

So I ask this to anyone who is aware of the IPCC's temperature increase predictions for the 2090-2099, with the upper boundary at 6.4°C relative to 1980-1999 levels, does something sound familiar?

As both a physical geographer and a person, the extreme, sensational events in Earth's recent history particularly fascinate me. My blog will review some of the literature on abrupt climate changes detailing the defining mechanisms and effects on Earth from the last Glacial Maximum through the Holocene (c. 22 kya to present) to present. With a greater understanding of why and how these events occurred, the effects of a future abrupt climate shift will be related to present day species and civilisations.

Abrupt climate changes, also termed as Dansgaard-Oescheger events, have occurred throughout Earth's history but their prevalence is most-accurately documented during the breakdown of the Last Glacial Period through the Holocene to the present. Many readers may have heard of the Younger Dryas stadial, or the 8200-year event which will be covered over the next couple of months. Abrupt climate changes have seen increased media popularity along with climate change coverage. Indeed, the popular 2004 film 'The Day After Tomorrow' and the 2009 film '2012' both depict catastrophic scenes of sea level rise causing mass-extinctions over much of Earth. Although these events are unlikely to occur in the 'Hollywoodified' time-scales mentioned in each film, c. 6 weeks - 6 months, abrupt climate change could occur over decades as found by the USGS in 2008.

In 2008, the US Geological Survey (USGS) published a report on Abrupt Climate Change which revealed some alarming potential consequences of anthropogenic warming. They concluded that Abrupt Climate Change occurs over "decades or less" causing "clear risks to society in terms of our ability to adapt". The summary brochure is a very informative read. However, I find the video/podcast below to be a brilliant explanation of what abrupt climate change is and how it may affect Earth in the next century. Have a listen!

I hope this short introduction has explained what I am interested in and what abrupt climate change is. In my next post, I will add further justification to studying abrupt climate shifts before considering the causes of the most-well documented event, the Younger Dryas. To whet the appetite, check out the simplified explanation below.

(1) Benton and Twitchett (2003) doi:10.1016/S0169-5347(03)00093-4