Sharper Focus

The two major satellite-based estimates of lower-troposphere temperature, from RSS and UAH, have published their December values to complete the year 2010. In both cases the annual average for 2010 ended up a close 2nd to 1998. Some eagerly anticipate the imminent GISS value for surface temperature for December, to complete 2010, as many expect the GISS annual average for 2010 to set a new record high. But we don’t need December’s value from GISS to continue our comparison between different temperature data sets.

Hottest Year

It’s near certain that in the GISS global temperature data set, 2010 will end up the hottest year on record. In fact some of those who deny the reality of global warming have already begun to “spin” the event, downplaying its significance by suggesting that observing the “hottest year” is no big deal. This, from the same people who believe in the mythical “levelling off” or “cooling” of temperatures over the last decade or so.

History of Arctic Sea Ice, part 2

Since satellite observations began, the extent of sea ice in the arctic has declined dramatically; this year the summer minimum extent was the 3rd-lowest on record. There is also considerable observational evidence that arctic sea ice extent over the last few decades is much lower than it has been for at least a century prior to modern times.

Yet to put such dramatic change in context, one hopes to stretch even further back in time. A team of researchers led by Leonid Polyak of Ohio State University’s Byrd Polar Research Center has culled the available evidence from hundreds of studies of proxy data for sea ice extent. As reported at Science Daily, in a recent paper in Quaternary Science reviews they report their findings: that the present extent of arctic sea ice is at its lowest for at least several thousand years.

It’s the Trend, Stupid

Anthony Watts posts that Southern Hemisphere Sea Ice Extent Anomaly for November was a record high for the NSIDC data set. He also mentions that this year saw record highs in Southern Hemisphere ice extent for June, July, and August as well.

Watts also complains that “Oddly, they have a plot for extent, and a data file for area, but no plot for area or data for extent. Seems backwards, doesn’t it? Maybe I’ve missed something and they are in some other FTP folder?” This makes me suspect that he hasn’t looked at the actual data files, because those files with “area” in the name contain data for both area and extent.

Open Thread

For stuff not on-topic in other threads.

Comparing Temperature Data Sets

In light of Anthony Watts’ latest idiocy comparing GISS and UAH temperature data without bothering to put them on the same scale, I thought it might be interesting to compare different temperature records … but let’s do it right, eh?

Odd Man Out

In a recent post Anthony Watts highlights the difference between the GISS global temperature for Nov.2010 and that from UAH (i.e., the UAH TLT or lower-troposphere temperature), saying:

Hide the Incline with the “Rank Trick”

or, Hey David Whitehouse — why is the sky orange?

It seems that David Whitehouse still doesn’t understand basic statistics. I mean the really basic stuff.

Imagine

Imagine there’s no Heaven
It’s easy if you try
No hell below us
Above us only sky
Imagine all the people
Living for today

Imagine there’s no countries
It isn’t hard to do
Nothing to kill or die for
And no religion too
Imagine all the people
Living life in peace

You may say I’m a dreamer
But I’m not the only one
I hope someday you’ll join us
And the world will be as one

Imagine no possessions
I wonder if you can
No need for greed or hunger
A brotherhood of man
Imagine all the people
Sharing all the world

You may say I’m a dreamer
But I’m not the only one
I hope someday you’ll join us
And the world will live as one

Prior Knowledge

Bayesian statistics offers rich rewards, including that it gives you a probability distribution for everything. But there’s always the pesky question of how to define what’s called the prior probability distribution, especially when we don’t have much information to go on. In such cases, we usually try to define a “non-informative” (or maybe “non-informed”) prior, i.e., one which doesn’t make any assumptions, and has the smallest possible impact on the final answer so we can let the data speak for themselves.