Yes, please try this at home!

It’s amazing the confusion that accompanies climate change questions. That’s partly because it is a complex subject. So it’s not surprising that people can make glaring mistakes.

Here’s one, though, that’s easy to get your head around by a simple experiment you can do at home. It relates to the question of melting of the ice sheets in Greenland and Antarctica. David Attenborough covered this in the last episode of “The Frozen Planet” screened here recently. His point – that global warming could cause loss of this land ice into the sea leading to dramatic increases in sea level.

Of course, this gets denied by the climate change deniers.  I came across one recently who suggested an experiment to prove Attenborough wrong:

” I can only suggest that every one do the following experiment. Take one half glass of water. Add two or three ice cubes. On the outside of the glass mark the level of the water. Leave for a few hours until the ice has melted entirely. Note the water level compared with the mark.”

Well, yes. Think about it – look at the image. Melting those ice cubes is not going to make much difference to the water level is it? Most of their volume is already under water and there already contributing to the water level.

This is why melting of floating icebergs due to global warming will have a relatively small effect.

But that’s not what Attenborough was talking about.

His comments related to movement of ice from the ice sheets on Greenland and Antarctica into the sea. Partly from melting. But also from sliding of the ice sheet in Greenland as the water melt lubricates the ice/rock junction. And in Antarctica the fear is that warmer sea temperatures will diminish the effect of pack ice restraining glacier ice from moving into the sea. In both cases the problem arises from addition of land ice to the sea.

So here’s the proper experiment:

Take one half glass of water. On the outside of the glass mark the level of the water. Now add your three ice cubes. Leave for a few hours until the ice has melted entirely. Note the water level compared with the mark.”

Or even quicker.

Note the water level immediately after addition of the ice cubes!

Think about it! Try it at home.

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Footnote: Much of the research on mechanisms of movement of these land ice sheets into the sea is relatively new. many of the current findings were jsut not available during preparation of the 1987 IPCC Fourth Assessment Report.  Consequently the concern is that the effects of climate warming may be greater than estimated by that review.

“Other ways of knowing” – some sense at last

There’s been a lot of rubbish written about “other ways of knowing”. So it’s quite refreshing to read Richard Carrier’s classification of methods of knowing. This is from his book Sense and Goodness Without God: A Defense of Metaphysical Naturalism. Well worthy reading by the way.

He starts by pointing out that no method of obtaining knowledge can produce absolute certainty. We can always be wrong, make mistakes. But we can list possible methods in order of reliability:

“What is rational is to assign degrees of conviction to degrees of certainty established by a tried-and-tested method. What is rational is reasonable certainty, not absolute certainty.”

“The methods of logic and mathematics are well-developed and provide the greatest certainty we have yet been able to find regarding anything, other than a present, uninterpreted experience. The next greatest certainty has been found in the application of scientific methods to empirical problems. In third place is our own daily experience, when interpreted with a logical or scientific mindset. Fourth is the application of critical-historical methods to claims about past events. Fifth is the application of the criteria of trust to the claims of experts. Sixth is the untested but logical application of inferential generalizations from incomplete facts—that is, plausible deductions. Such is the scale of methods that we have historically been able to discover and confirm as effective.”

“Experience shows that our degree of certainty will generally be weaker with regard to facts at each stage down this six-rung ladder, though within each category lies its own continuum of certainty and uncertainty, and the ladder itself is a continuum of precision and access to information: the more data we have to ground our conclusions, the farther up the ladder we find ourselves. Thus, mathematics is just perfected science; science, perfected experience; experience, perfected history; and history, perfected attention to experts; while plausible inference is what we are left with when we have none of those things.”

“Lacking any of the above approaches to the truth, we are faced with untrustworthy hearsay and pure speculation, where only the feeblest of certainty can ever be justified, if at all.”

Carrier writes that accurate methods of knowing have the properties of predictive success and convergent accumulation of consistent results.  However, these should be evaluated intelligently. Even the best method may produce faulty knowledge if used incorrectly.

So how do the different methods rate?: