LOOKING BACK AT CO2 AND AHEAD AT TROUBLE

'Scary' climate message from past
Richard Black, 10 October 2009 (BBC News)

"A new historical record of carbon dioxide levels [in ocean sediments going back 20 million years] suggests current political targets on climate may be "playing with fire", scientists say…

"Levels similar to those now commonly regarded as adequate to tackle climate change were associated with sea levels 25-40m (80-130 ft) higher than today…Scientists write [Monsoons and Meltdowns] in the journal Science that this extends knowledge of the link between CO2 and climate back in time."

Studying the details of the most recent IPCC report is pretty disturbing. (click to enlarge)

"The last 800,000 years have been mapped relatively well from ice cores drilled in Antarctica…But…the new record contains much more precise estimates of historical records than have been available before for the 20 million year timeframe [into the Miocene period]…

"At the start of the period, carbon dioxide concentrations in the atmosphere stood at about 400 parts per million (ppm) [probably sustained by prolonged volcanic activity] before beginning to decline about 14 million years ago - a trend that eventually led to formation of the Antarctic icecap and perennial sea ice cover in the Arctic…[I]n the last few million years [CO2 concentrations have been much lower, cycling] between 180ppm and 280ppm in rhythm with the sequence of ice ages and warmer interglacial periods."

It's time to do something. (click to enlarge)

"Now, humanity's emissions of greenhouse gases are pushing towards the 400ppm range, which will very likely be reached within a decade…[When CO2 was at those levels, there was no icecap on Antarctica, sea levels were 25-40m higher and temperatures were about 3-6C (5-11F) higher than today]… The new research does not imply that reaching CO2 levels this high would definitely result in huge sea level changes, or that these would happen quickly…just that sustaining such levels on a long timescale might produce such changes…"

[Jonathan Overpeck, co-chair of the Intergovernmental Panel on Climate Change (IPCC) 2007 report and climate scientist at the University of Arizona:] "If anyone still doubts the link between CO2 and climate, they should read this paper…[W]e don't know where the critical CO2 or temperature threshold is…It could be below 450ppm, but it is more likely higher - not necessarily a lot higher - than 450ppm…But what this new work suggests is that... efforts to stabilise at 450ppm should avoid going up above that level prior to stabilisation - that is, some sort of 'overshoot' above 450ppm on the way to stabilisation could be playing with fire."