The preliminary results of a drill by the ANDRILL (Antarctic Geological Drilling) were published in the print edition of Nature this week.
It has shown a history of the previous retreat and collapses of the West Antarctic Ice Sheet (WAIS). The WAIS melt with its vast stores of solid water, and even more in the glaciers on the Antarctic continent itself has the capability to massively change sealevels in metres rather than centimetres.
In January 2006, in a UK government-commissioned report, the head of the British Antarctic Survey, Chris Rapley, warned that this huge west Antarctic ice sheet may be starting to disintegrate, an event that could raise sea levels by approximately 5 metres (16 ft). Rapley said a previous Intergovernmental Panel on Climate Change report playing down worries about the ice sheet’s stability should be revised. “The last IPCC report characterized Antarctica as a slumbering giant in terms of climate change,” he wrote. “I would say it is now an awakened giant. There is real concern.”  Note that the IPCC report did not use the words “slumbering giant”.
Hot topic says that ANDRILL
.. drilled a 1,280 metre core from the seabed under the Ross Ice Shelf. It’s the longest and most complete drill core recovered from Antarctica, and was made possible by drilling technology developed by a team at the Antarctic Research Centre at Victoria University of Wellington led by Alex Pyne.
The ANDRILL core documents 38 advances and retreats of the ice sheet, and suggests that during the warm Pliocene the key driver could have been the ‘obliquity’ cycle in the earth’s orbit around the sun â€” a 40,000 year tilt in the Earth’s axis towards and away from the sun that affects the length of summers at the poles. New modelling of the ice sheet2 confirms the link with the obliquity cycle, and suggests that the primary mechanism is melting of the base of the ice sheet by warm oceanic waters â€” a process that has already started.
The “warm” Pliocene period that the Nature article covers 2-5 million years ago, when the natural carbon balance CO2 levels were about 400ppm. This is roughly the same level that anthropogenic emissions of CO2 are pushing us to as this table from wikipedia shows.
|Gas||Preindustrial Level||Current Level||Increase since 1750||Radiative forcing2) (W/m|
|Carbon dioxide||280 ppm||387ppm||104 ppm||1.46|
|Methane||700 ppb||1,745 ppb||1,045 ppb||0.48|
|Nitrous oxide||270 ppb||314 ppb||44 ppb||0.15|
|CFC-12||0||533 ppt||533 ppt||0.17|
The link between CO2 levels and world temperature levels can be clearly seen in the Vostok ice core left (click for a bigger picture). Other cores from recent geological history show the same correlation.
This is caused by the well established greenhouse effect of greenhouse gases causing thermal retention inside the atmosphere, and the consequent heat adsorbtion by water bodies. This is relatively simple science and can be demonstrated easily in both the lab and in glasshouses (where the glass has a similar effect).
On the chart on the right it shows the causes of anthropogenic CO2 production. This shows the rapid increases since the start of large scale industrial use of fossilised carbon.
Various buffering effects into the oceans and other carbon sinks diminish the amount of CO2 that is retained in the atmosphere. This is shown in the chart below.
It is clear that the buffering by carbon sinks has diminished the amount of CO2 present in the atmosphere, however not by enough. The CO2 levels are still rising.
It is easy to show using isotopic ratios of the carbon and oxygen of CO2 in the atmosphere that most of the rising CO2 is from fossilised carbon. In fact my geochemistry text book from 1980 has all of the evidence (but isn’t online).
A frequent protest from CCD’s is that changes in greenhouse gases through natural mechanisms like volcanoes and the related climate change are normal. Similarly they’d argue that there are external cyclic factors that change climate.
These arguments are both correct and also totally fatuous. They show a clear lack of understanding of cardon cycle processes.
The current output of anthropogenic CO2 emissions is on top of any natural events. The ‘normal’ carbon cycle accounts for about 95% of the CO2 in the carbon cycle. However these are balanced for at least the last 10,000 years in that releases into the atmosphere are largely balanced by sequestration into carbon sinks like plants, seashells or oceans. The extra generation by volcanic events caused minor short-term spiking, but was sucked up into a carbon sinks within short time frames. Unfortunately the sustained emissions of anthropogenic CO2 is being put into the atmosphere is in excess of the carbon balance sinks capabilities to adsorb. Consequently the atmospheric and ocean CO2 levels are rising.
The ANDRILL findings should give pause to the Climate Change Deniers (CCD’s) in the sitting select committee looking at how to fulfil our obligations under the Kyoto protocol. It clearly shows that at similar levels to our current atmospheric CO2 level, there were massive melts in the WAIS. This also releases the brake that constrains the movement of the glaciers behind the ice sheet.
As Greenpeace points out in a rather conservative press release
Publication of the research follows a climate congress in Copenhagen last week, where over 2,500 climate scientists and researchers issued an urgent plea to political leaders to get on with addressing climate change. Key messages from the Congress included statements that:
- The worst-case scenarios put forward Intergovernmental Panel on Climate Change (or even worse) are being realised.
- There is no excuse for inaction.
- The influence of ‘vested interests that increase emissions” must be reduced.
- Regardless of how dangerous climate change is defined, rapid, sustained and effective mitigation is required to avoid reaching it.
From my early training in Earth Sciences, I’d have to concur. Irreversible anthropogenic generated climate change is under way. What we are looking at now is if we can start mitigate the effects that will happen within my remaining lifetime.
* John Key and John Boscawen (ACT MP on the select committee on climate change) come to mind after reading this vacuous exchange. Neither appear to understand the issue and think of it as being narrowly political and economic rather than affecting peoples lives.