Where Grey Matter meets Dark Matter

<< Previous Episode | Episode List | Next Episode >>

Episode 6 - 8 March 2009

Note: This interview with Tim Cowan occurred on the 18th of January, 2009, several weeks before the severe bushfires in south eastern Australia on the the 7th of February. The government has initiated a Royal Commission into the causes and response to the fire, and as such, CSIRO employees have been banned from speaking to the media on the subject. On listening back to the intro to the interview with Tim Cowan, we realise we may have given the impression that the interview took place after the fires. What we meant to say in the introduction was that we wanted to do another interview specifically about the fires, but of course he wasn't able to, so we used this earlier one instead. Tim's a good guy - we don't want him to get in trouble with The Man.

Few things have excited the passions of so many more than the idea of global warming. Although the basic tenets are no longer seriously debated in scientific circles, the political, economic, and yes, pseudoscientific, debates still take up tabloid space.

We spoke to Tim Cowan who works on climate models at CSIRO, specifically the ocean/atmosphere interface (where they meet) and he filled us in on what the latest models are predicting. It looks like aerosols are playing a bigger role than previously thought.

The earth's atmosphere is a complicated mix of gaseous chemicals (mostly water) and bits of crap. These bits of crap are the aerosols Tim was talking about. They are usually sea-salt grains, soot and smoke, ice and unburnt hydrocarbons (like petrol). While many of these come from the same sources as greenhouse gases, aerosols have the opposite effect - they cool the planet. While they don't come close to offsetting the warming effect of the CO2 and other greenhouse gases, they are making predictions more difficult.

Another complicating factor that has shown up in some of the models is what's called the Global Conveyor. This is a worldwide system of ocean currents that move water (and heat) between oceans and between hemispheres. So while the atmospheres of the northern and southern hemispheres are relatively isolated from one another, the conveyor connects them in an important way. In fact, the new results apparently show that the northern hemisphere is warming by less than expected because the currents are carrying a lot of the heat to the southern hemisphere. So the dirty northerners, with all their filthy pollution are not as bad off as they could be - because they are dumping the heat on us.

We also discussed the El Niño Southern Oscillation (ENSO) which is a system of ocean/atmosphere effects involving warming of the ocean off Peru and subsequent shifting of the weather patterns in the southern Pacific. There is also the opposite effect, called La Niña. These systems can be correlated with unusually wet and unusually dry periods in Australia.

Note that Tim was talking about computer simulations of climate, not observations. However, there is a lot of reason to place confidence in the qualitative predictions (the general idea) of these models, even if the quantitative detail (the exact data that comes out) is suspect. For instance, the models are initially set at a time some distance in the past, and they are then run up until the present. Now a good test of the accuracy of the model is how well it predicts current observations - and these predictions turn out to be quite good. Also, even though individual models may need to be treated with a degree of caution, if there are many different models, with many different parameters all saying roughly the same thing, then that should raise the confidence in all the models.

But while scientists argue about scientific detail, and non-scientist fools argue about non-existent global warming conspiracies, one thing is a certainty, this argument will keep generating a lot of heat (there, we made the obvious pun, so sue us).

For a list of Tim's publications see: http://www.cmar.csiro.au/search/pubsearch.htm. Here is a choice selection:

  • Cai, W. J., and Cowan, T. D. (2007). Impacts of increasing anthropogenic aerosols on the atmospheric circulation trends of the Southern Hemisphere: An air-sea positive feedback. Geophysical Research Letters, 34 (L23709): doi:10.1029/2007GL031706.
  • Shi, G., Ribbe, J., Cai, W. J., and Cowan, T. D. (2008). An Interpretation of Australian Rainfall Projections . Geophysical Research Letters, 35 (2): 2702.
  • Cai, W. J., and Cowan, T. D. (2008). Evidence of impacts from rising temperature on inflows to the Murray-Darling Basin. Geophysical Research Letters, 35: doi:10.1029/2008GL033390.

BETA: A couple of members of the Cosmic Crew wasted whole summers playing games in the Fallout series. The first game is recognised as one of the great games of all time (meaning: 'since the late 1970s'). It was a role playing game (RPG to those in the know) set in the western USA many years after a global nuclear war. The world as we know it has been transformed into a hostile wasteland, with drugs, violence and mutants waiting behind every crumbling factory and burned-out car - something like Adelaide. But how do you survive the initial barrage of bombs to reach this paradise on earth? Well our hero in the game had the luxury of a 'vault' - a giant underground cavern that protects its inhabitants until it's safe to leave. But vaults are just fiction (or are they?) - we need a practical plan to get through.

It's as easy as ABCBA:

            A vert   (your eyes)

            B arrier (for your body)

            C over  (your head and vitals)

            B lock   (your ears)

            A gape  (your mouth)

A: Don't look at the flash. You'll need those eyes to fend off bandits and mutated wombats.

B: If you can't get underground, then get behind something sturdy like concrete or a strong brick wall. Do not shelter behind a window. Maybe get in a swimming pool.

C: The most important parts of your body need to be protected. The same rationale as applies for bike helmets.

B: The blast is going to be LOUD! Make sure you cover your ears.

A: A loud noise is just a big change in air pressure, open your mouth to allow the pressure to equalise as quickly as possible.

So just add one more acronym to your nuclear vocabulary (WMD, NTBT, MAD) -

"Now tell me right out loud, what are you supposed to do when you see the flash: ABCBA!"



Oops. Mistakes we shouldn't have made but did:

When Anthony was waffling about beta particles scattering 'electrons in your nucleus' he meant to say 'electrons in your atoms'.

Chris mentioned that you shouldn't stare at a total solar eclipse. Actually, you shouldn't stare at the sun at all. The thing that makes total eclipses dangerous is that even though they aren't very bright, they still give off lots of other radiation. Human bodies are designed to react to visible light: you'll feel pain if you stare at a bright light, and your pupils will contract to minimise the amount of radiation coming in. But if it's not visible light, say infrared or ultraviolet (which is mainly what goes into your eyes during a total eclipse) then your body doesn't notice and doesn't react. End result = blindness.

Anthony suggested that Florey and Fleming worked together, but while Florey definitely read and followed Fleming's work on penicillin, we could not find evidence that they worked together.

Wikipedia tells us that Ernest Rutherford had one child, a daughter called Eileen.

The Rutherford model of the atom was important because it put most of the atom's mass and all of its positive charge in a tiny nucleus at the centre. If this were not true, and the nucleus were more spread out, then the positive charge would be too diffuse to be able to transfer enough momentum to the alpha particles for them to spit out the way they went in. Complicated - read a book on electromagnetism.

Voyager 1 launched on Sept 5, 1977. It visited the planets Jupiter and Saturn. It is now the furthest probe from Earth at a distance of 16.2 billion kms, a bit over 100 times the distance between the sun and the earth. Voyager 2 was launched earlier, on 20 August 1977, but was much slower. However, it visited all four gas giants - it is the only probe to have gone to Neptune and Uranus. Since it is moving slower than Voyager 1, it is not as far away - 13.1 billion kms. And they are both still transmitting: http://voyager.jpl.nasa.gov/mission/weekly-reports/index.htm.

Your friendly-neighbourhood Spiderman used to have a webslinger gun which was attached to his wrist - but then in 2004, in the "Disassembled" series, they gave him organic/biological web shooters. So Spidey evolves, even if only to keep up with modern technology. (Did someone say "Carbon nano-tubes"?)


©2009 Cosmic Tea Party | Privacy Policy | Email: contact 'at' cosmicteaparty.org