They don't. A running average like that introduces a time lag.
Anyway read something like this.
You're oh so sure about a time lag, but maybe there is none.
I'd be really suprised if a time lag holds up, even if it's only 200 years, and even if it only holds true for the polar regions.
Now that's digging deep to continue the fantasy. These are guys rejecting the idiotic AGW theory and giving reasons why the ice cores would simply be off in their CO2 records, results of artifacts.
Alas, nothing here helps you any. This was done before they got clever and started dating the actual air a few years back. They date it by measuring the relative quantities of isotopes. This does indeed lead to an accurate dating method compared to the ice. Any corruption by conditions as it was formed would alter the age of both ice and air, not just one. Any mixing of air simply mixes the CO2 at the same rate it mixes the age. The relative change in CO2 over time would trend from year to year, just as it would if it were the same age as the ice. The isotope levels and the CO2 content would both be contaminated equally, making the dating just as reliable as if there were no mixing.
It makes no sense. Oceans mitigate temperature fluctuations, they don't speed them up (at most it'll seem the oceans slow them down, which would require that temperature lags CO2 buildup).
Exactly. It makes no sense. Why? Because CO2 does dick and you're convinced it's the whole shebang. It's a byproduct of the temperature change, not the cause. The oceans slow down temperature changes because they take so much longer to change themselves. This is why CO2 lags, because it had fuck all to do with the actual temperature increase or decrease in the first place, and is simply a result of the oceans changing their capacity to hold CO2.
"The layer of porous firn on Antarctic ice sheets is 50–150 m deep"
Also, one year is compressed into a layer of less than 1 cm thick.
Yes, it takes a long time. It's how they got Vostok down to a date range of 200-1000 for an actual CO2 lag when they started dating the air. It's why the people taking Epica as a good source for recent temperatures are fucking morons for picking the slowest building ice on the planet. It's the oldest record, and the least accurate. The actual snowfall isn't as bad as you make it sound though, that 1cm thick ice starts out as average precipitation of ~16cm, which is quite a bit more than 16cm in snow. A meter only takes a few years to build, not hundreds. As it compresses, much of it evaporates off, leaving you with a fraction of the original ice before it solidifies.
The extreme age gap typically isn't a product of the conversion to ice in the first place. They got several thousand years of an age gap in Vostok because of the depth. At the extreme end of the time scale, the resolution goes to absolute crap. The depth of the ice results in immense pressure creating loads of little micro fractures in the ice, and over hundreds of thousands of years, that's a lot of time for the air to mix between the high pressure bubbles they connect up. A couple hundred thousand years up the core, there was nothing like that and the resolution steadily increased.
How the hell are you going to get perfect data from that, huh? There's a lot of potential for noise and even biased noise.
So BEFORE you start shouting that CO2 lags T, you should be very, very, very sure that those ice cores are actually reliable in this respect.
Can they REALLY give you a reliable resolution of 100 years ??
But you people think it's meaningful...
The ice core temperature records are peer reviewed science. They're the foundation of AGW. The hard science that says look, CO2 and temperature rise and fall together! They don't say what AGW says they say, but they're the foundation none the less. It's not me you have to convince.
Can they give resolution of 100 years? Not for much of it. Why would they need to though? It takes thousands of years to go in and out of an interglacial. We're looking at the trend lines over millennia, not year to year fluctuations. If it went up one year and down the next, that would be completely non-existent in the record. Fortunately, no one gives a shit. Whether a believe or a skeptic, fluctuations are irrelevant.
Edit: I spent almost an hour editing the insults out of a post yesterday. I wouldn't worry that much about the tone of the posts.