On 08/08/2019 09:12, Spike wrote:
On 07/08/2019 21:48, JGD wrote:
On 07/08/2019 17:45, Spike wrote:

The Vostok ice cores showed that CO2 levels *lag* temperature levels
rather than leading them, over a time span of some hundreds of thousands
of years.

That's quite an old chestnut now. See eg:

https://www.youtube.com/watch?v=dHozjOYHQdE

Interesting.

The presenter said in short that the CO2/temperature issue was one of
one sometimes leading, and sometimes following, the other, the
perturbing agent being Milankovich cycles,

They did explain it in the clip. Basically in the present geological era
the south pole almost always lags the rest of the planet because it is
cut off from the rest of the land masses by the roaring forties oceans.

It was not always the case. When there were land masses spread in a
different pattern then things were different. But with the continents as
they are presently positioned on the Earth insolation at 70N is a pretty
good proxy for the global temperature from solar forcing. This page
isn't a bad introduction if you actually want to learn some physics:

http://www.atmos.albany.edu/facstaff...ariations.html

The north pole has no solid land mass at the pole but there is a *lot*
of land at high latitudes with huge forests in near permanent sunlight
during the summers. CO2 concentration has much wider variation near the
north pole than elsewhere. By comparison the south pole concentration
lags any changes by a few ppm and shows a much smaller annual variation.

http://scrippsco2.ucsd.edu/graphics_...tration_trends

Point Barrow 70N has already been above 415ppm and may touch 420 this
year. With an annual peak to peak variation of ~20ppm

Christmas Island at the equator is about 407ppm with 8ppm peak to peak.

South Pole is just below 405ppm with about 2ppm peak to peak variation.

Unfortunately, this raises more questions than it answers. One such is
that where in the Vostok record is this shown? What records do in fact
show this? What is the mechanism whereby a lead changes to a lag?

I will assume that you are asking for information here.

The ice core can be used multiple ways as can ocean sediment cores.

The gas bubbles trapped in it can be analysed as samples of the
atmosphere at the time the snow was laid down.

The isotope ratios of the oxygen and carbon in it can be used to infer
the volume of water remaining in the oceans. Precipitation is
preferentially of the lower mass isotopes (as is photosynthetic uptake).

Other slow growing long lived things that lay down calcium carbonate.
Notably deep water corals and stalactites can also be used to do stable
isotope analysis and work out how much of the oceans were liquid and how
much water was locked up as solid ice glaciers. Things with regular
growth cycles are prized because you can count the rings to date them.

And the big one: if this is all caused by the influence of Jupiter and
Saturn's gravity fields, why are we being strongly encouraged to go
vegetarian, and not to till the soil, in order to help the planet? (BBC
R4 'news' this morning). Eating soyaburgers won't perturb Jupiter at all.

The ice age cycles work on geological timescales. We are presently
wrecking the planet on a timescale that is at most centuries and could
well do irreversible damage within decades if we haven't already.

I don't see much prospect of our politicians doing anything sensible
about it. You can be sure though that they will blame the scientists for
not shouting loudly enough when the chickens come home to roost.

--
Regards,
Martin Brown