Jennifer Marohasy

a forum for the discussion of issues concerning the natural environment

Archives for November 28, 2005

C02 Follows Temperature In Bubble Record

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Three fascinating papers were published in Science (Vol 310, 25th November 2005) last week on climate change and the relationship between carbon dioxide, methane and nitrous oxide levels and temperature over the last 650,000 years.

They report on new findings from the European Project for Ice Coring in the Antartica.

A graph in the ‘perspectives section’ by Brook (pg 1286) summarizes the findings,
view image (70 kbs).

The data tells me that:

1. The greenhouse gases are at higher levels now than they have been over the last 650,000 years.

2. Carbon dioxide levels correlated with temperature and have peak during previous interglacial warm periods just below 300ppm, view image (120 kbs).

3. In the past, increases in atmospheric carbon dioxide levels have tended to follow, rather than preceded, rises in temperature.

4. We are currently in an interglacial warm period and these periods tend to be followed by very cold periods.

I find the graphs fascinating.

While atmospheric carbon dioxide levels have clearly fluctuated with temperature in the past, they have tended to lag behind temperature. This doesn’t accord with the current perception – what is understood to be the current consensus which is that carbon dioxide drives temperature?

I find the prospect of another ice age really scary. The graphs suggest to me that one is imminent – like in the next few hundred or thousand years? However, greenhouses gases have never been so high.

It is perhaps interesting to ponder …. If we were able to influence climate in a predictable way, and if we could delay indefinitely the onset of the next ice age, should we?

…………….

Many, many thanks to the reader of this blog who sent me copies of the papers. There has been some discussion of the papers at the Real Climate blog, http://www.realclimate.org/index.php?p=221&lp_lang_view=en .

Rising Salt Problem in WA

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A main premise of the following guest post from Boxer* is that across the West Australian wheatbelt, water tables are showing an upward trend. Boxer explains the problem and the need to act now if we are to learn from history and avoid the problems that destroyed, for example, agriculture in the valleys of the once fertile Tigris and Euphrates Rivers.

I have asked Boxer for a link to some data that quantifies the extent of the rising water table problem. He has responded that:

There is no single place that I can find where a large amount of water table data is assembled in one place. This is not because there is a paucity of data, but I think because there is so much data, and the fundamental cause and effect of dryland salinity has been so well established for so long, that the publications over the last decade or two do not directly present water table data. The scientific debate has moved on.

If a problem is complex and widespread, all the more reason, in my opinion, to have a few agreed indicators and regularly report on how they are trending. Others may see things differently? The issue is important. Let’s have some discussion. Here’s the post:

Like a number of other people who comment on this blog, I enjoyed Jennifer’s recent piece on Ockham’s Razor (ABC Radio, http://www.abc.net.au/rn/science/ockham/stories/s1509193.htm ) in which she addressed the arguments of various doomsday prophets such as Tim Flannery and Ian Lowe.

The Prophets of Doom have a list of iconic issues. I think it is healthy for the Prophets to be challenged because they have a vested interest in, for example, arguing that climate change will be the end of all things, just as coal miners have a vested interest in business as usual. Challenge them both.

On the issue of salinity however, I argue that dryland salinity is a major issue for this country. On this one, I am with the doomsday crowd. My vested interest? My professional life is bound up in finding ways for agriculture to adapt to rising water tables and perhaps even find ways to prevent the problem becoming as bad as the models predict.

Jennifer uses the example of the Murray River, where, at a point just upstream from the off-take for Adelaide’s water supply, salinity levels have fallen over the last couple of decades due to salt diversion work. Good news, but is that a reasonable reflection of the state of affairs in the whole river system? I don