physics

Up until now I have unthinkingly assumed that melting sea ice doesn't change sea levels. The reason is a basic principle of physics: Archimedes' Principle, which says that a floating object displaces its own weight of liquid. The idea is that when the ice melts, it will exactly fill in the 'space' that the ice block made in the water, thus leaving the water level unchanged.

But there's a fly in the ointment: when sea ice freezes, it preferentially expels salt, in the process becoming purer than the sea water it is floating in. Pure water is less dense than salty water, so when the ice melts it will overflow the 'hole in the water' that the ice had occupied, and when it overflows, it raises the water level.

That's true, and that's a very interesting application of physics and a lesson to think precisely about the physics of any situation. In other words, as physics, it is fun and interesting.

But let's see how this is being used. At the alarmist site Skeptical Science, which purports to 'expose' the fallacies of skeptical views on global warming, they start out:

In a previous post on peacelegacy.org,I used the example of a chappie called Fred to show you why the absence of an atmospheric hotspot is, all by itself, a complete disproof of the hypothesis of dangerous anthropogenic global warming (AGW). For those who came in late, the entire basis for the AGW claim is that certain unverified, and now falsified, computer models predict a lot of warming over the coming 100 years. It is shocking, but true, that there is no actual evidence whatsoever for this idea; it is computer models alone, and those models are basically no more than coded guesswork. And what do these models predict?

They predict that the world is heated by the appearance of a 'hotspot' in the atmosphere above the equator.

Model predicts air above the tropics heats up. from the NIPCC Report p. 107
But the reality is that this hotspot has failed to develop:

I see they're going to fire up the Large Hadron Collider at half power. For those who haven't been following this story, your life is being put at risk.

The Large Hadron Collider (LHC) is a project by The European Organization for Nuclear Research, known as CERN. Back in 1964, a physicist called Peter Higgs found an elegant mathematical theory by which he explained one of the great puzzles of particle physics, why mass exists.

There is some background to this question. The twentieth century produced two great theories of physics: relativity and quantum mechanics. Quantum mechanics explained many curious puzzles in the subatomic realm, for example, why atoms don't collapse. Atoms have a field of electrons orbiting the nucleus; according to classical mechanics, any accelerating charged particle (like an electron orbiting an atom) should radiate energy. This means the electron should spiral into the nucleus and the atom should collapse. Obviously they don't because we are still here, made of functioning atoms! Another example is the radiation from black bodies. Only quantum theory can explain why the spectrum is what it is.

It is no exaggeration to say that the modern world only exists because of quantum mechanics: every piece of electronics that exists only works because of quantum mechanics, and a great deal of it was only discovered because we understood the theory behind it all. It is the most successful scientific theory ever. It has passed every experimental test ever thrown at it. But it doesn't explain gravity.

This is a reasonably short work, very different from Ian Plimer's Heaven and Earth. Although Paltridge is an atmospheric physicist and erstwhile Chief Research Scientist with Australia's CSIRO, he has put together an accessible summary of some of the damning evidence against the global warming alarmism.