Global warming and CO2

Highlights of Gary’s progress on the

Our Far South Expedition

March 2, 2012

 Global warming and CO₂

Ice core records show that atmospheric CO₂ levels and temperature are intimately linked and that both have varied cyclically over a 100 thousand year timescale between about 180 and 280 parts per million, with low CO₂ levels representing past glaciations and high CO₂ levels representing interglacial or warm periods.

 The warm up phase has been rapid and the cooling phase has taken much longer. Peak warmth generally lasted a few thousand to 10,000 years. Our current position in the natural cycle would imply that we should now see reducing CO₂ and cooling. But we are not. In fact, CO₂ levels are now above 380 parts per million and the last time the earth saw those levels was several million years ago. And, Antarctic geological research indicates that at those times, the Ross Ice Shelf collapsed and linked climate and ice sheet models tell us that the West Antarctic Ice Sheet also melted driven primarily by warmer waters underneath floating parts of the ice sheets and shelves. Such melting would result in a rise of global sea level of between 3 and 7 metres once you put that ice back into the ocean (this is not even considering what would happen in Greenland). How fast would that happen? Maybe as quickly as 400 years, but more work is required here to determine that rate as well as quite whether the rate is uniform over that time period. 

Crabeater Seal

One thing we do know is that man is continuing to pump CO₂ into the atmosphere at unconstrained rates, and that we are seeing signs consistent with the predicted warming: warming oceans, melting ice shelves – a relatively new lesson is that it is warming faster at the poles than the equator (a concept known as polar amplification), which is a little frightening as those are the regions most vulnerable to warming. And, what of all that additional CO₂ in the atmosphere, well a lot of it is being absorbed by the southern ocean and measurements show that this is making the ocean more acidic. What are the side effects of that? Can we stop the rise in atmospheric CO₂? That’s a hard one, given our fossil fuel addiction, but, another thing we do know is that even if we stopped tomorrow, we would still see the effects for a hundred or more years, so some degree of adaptation is going to be required. And, that begs the questions of what are the wider effects on sea-level, climate, fisheries…? And, how much? How fast? And especially what might we expect in “our own backyard”?

Still coming up …. Campbell Island