14 April 2008

Whatever Spins Your Top, Terra

Here is an interesting way to gauge the Earth's heat content: the Earth's rate of spin on its axis. This is how it works: when the Earth is warming, polar ice melts and the water distributes itself outward--away from the polar axes. This causes the Earth to slow its spin. When the Earth cools, more polar ice accumulates, bringing more mass in line with the polar axes--the Earth's spin speeds up.It is an indirect and rather elegant way to measure polar ice, and Earth's heat content.
The IERS determines the rotation of the Earth. Data only exists from 1972 to the present. From 1972 thru 1998 (26 years) 21 leap seconds were added. From 1999 to the present (9 years) only 1 leap second has been added. This means since 1999 to the present the Earth's rate of rotation has increased. There are two possible (but not mutually exclusive) causes for this. 1. Some of the Earth's mass has moved closer to the Earth's axis of rotation similar to a spinning skater bringing his arms closer to his sides, and thus spinning faster. For the Earth this would occur when some of its ocean water is moved to the polar ice caps to form snow and ice. Satellite data shows the Earth's atmosphere has been cooling since 1998. This would cause a build up of snow and ice at the polar ice caps and thus increase the Earth's rate of rotation. The time lines for the increase in the Earth's rotation and the atmosphere's cooling match. The Ice Caps are growing. __IceCap (PDF)
Another alternative is that the decrease in the sun's magnetic field reduces the induced EMF in Earth's conductors (oceans and ionized atmosphere). But that effect is apparently too small to account for observed speeding of Terra's top. Yet another alternative would be if geologic activity deep within the Earth was causing a rearrangement of Earth's mass closer to its axis. But that would take longer than just the last several years.

So it appears that Earth is spinning up to maintain conservation of angular momentum. Interesting, eh?

And what does the sea ice actually measure recently?
Arctic sea ice is now about the same as 1980. Antarctic sea ice is 1.5 million square kilometers more than 1980. __Heliogenicclimate__via__TomNelson


Plus, you may want to check out a guest article from David Smith over at WattsUpWithThat: Mixed Signals. H/T Tom Nelson

A lot of people are starting to look at the many different climate signals and are putting the pieces of the puzzle together, slowly but surely. And there is no guarantee that the "big herd consensus" is going to like how it all shapes up.

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