Ö÷²¥´óÐã

Congratulations on a superb programme. Two things: First, if I'd known how good it was going to be I'd have recorded it (we can't use the iplayer here in Dublin). Will it be repeated any time soon on and of Ö÷²¥´óÐã 1,2, 3 or 4 as I intend reviewing it on my blog [Broken URL removed by Moderator] ?
And second, you summarized very succinctly why none of us will ever see another ice age; 1) where we are on the perihelion cycle, 2) the Earth's tilt and 3? Could you drop me a line with that succinct summary again please? Thanks! Anthony.

Where did 60,000 years until the next ice age come from? Your Mr.Black indicates 1,500 years...

see /news/science-environment-16439807

also I think you forgot to mention the wobble of the earths axis as another contibuting factor to the cycle to the ice age

Kate Humble climbed a mountain in Scotland at perihelion to get closer to the Sun. Instead, she should have got on a plane and gone to anywhere near the Tropic of Capricorn and then at midday she would have been something like 2000 miles closer to the Sun. Even London would have been closer! Dumb TV science again...

Actually, I think it would have been more like 3900 miles closer to the Sun at the Tropic of Capricorn not 2000 miles, but you get the idea. Should've done my sums before commenting...

Why did you spoil an otherwise excellent and scientifically sound programme by ending it with the blaming of thinning arctic ice on human activity?
There is absolutely no scientific evidence for this - instead you pandered to the Ö÷²¥´óÐã's bias and the errors perpetrated by the IPCC.
Explain please why :
- no discernible global temperature change since 1998 (despite CO2 rising)
- though Artic ice may be thinning, Antarctic ice is increasing
- sea levels are not rising (despite the protestations of the Maldivan government)

Was this a science programme or a travelogue? I'm struggling to tell the difference nowadays.

Next week: Kate visits Copacabana beach to pick up a handful of sand, while Helen goes skiing in Klosters to show us what snow looks like in winter.

Kate Humble states that the Aurora Borealis is caused by 'radioactive particles' hitting the top of the Earth's atmosphere. I have always thought that the particles involved were mainly electrons and protons. Neither of these undergo radioactive decay. Has she other information?

I've just noticed that Malcolm Soo (above) has the same query as me. In this episode Kate Humble describes the solar wind as consisting of 'radioactive particles'. Also on a previous page titled: 'The Sun and the Solar Wind: Earth has been spared the fate of Mars' - Stephen Marsh: Series Producer, said: - "Every day we are hit by a blizzard of radioactive particles. It's called the solar wind". But are any of these particles heavy enough to be 'radioactive'? (i.e. subject to decay)? Is it correct to describe these particles as 'radioactive'?

This is what happens when you throw technical terms around carelessly. Solar wind is plasma, that's all. Nothing to do with nuclear reactions, except its energy comes from the fusion reactions in the sun's core.
(Since I'm here again, I'm going to revise my figure from before again to 3300 miles...)
Can we have some care with scientific terms please...

Great programme.

Does anyone know when Episode 2 will be repeated as my Dad missed it and has no access to iPlayer.

When will episode 2 be repeated on Ö÷²¥´óÐã HD? Last week Episode 1 was repeated on Tuesday at 2300 which was far too late. How are we supposed to know when these will be? Many people can now get Freeview HD and a programme like this looks much better in HD. I can't find an online searchable schedule of Ö÷²¥´óÐã programmes - is there one and if not why not?

I have read of a condition called 'precession' which (long story short) means the tilt of the earth changes every 25800 years causing hitherto summer to be winter and vice versa. I have only ever seen or heard of one reference to this. Any comments please?

One might be forgiven for expecting a programme devoted so much to the Earth's orbit and tilt to mention the precession to which Rob Brown refers. This effect is the result of an external torque on the Earth by the Sun's gravity. The Earth is not spherical, but 'squashed' at the poles due to its daily rotation. The equatorial bulge nearer the Sun experiences a force which is not exactly counteracted by the farther bulge, resulting in a torque, and this causes the rotational 'axis' to precess.

If we are to be more scientific, then we need to recognise that in general, a free moving body does not 'rotate' about a fixed axis. It moves in a complicated rolling and tumbling fashion which is clearly seen in the motion of many asteroids. Often the motion can reasonably be approximated as mere rotation, as is usually the case with the Earth, but care must be taken here. There is a question posed on this site about whether or not the Earth's axis can be shifted by an Earthquake. Assuming that the Earth has a fixed rotational axis which is shifted by an Earthquake is wrong on both counts. If the Earth had a fixed rotational axis, then an external torque would be needed to shift it to a different rotational axis. As all of the forces in an Earthquake are internal, an Earthquake can't do this. The motion of a free moving rigid body can be described as having a precessing rotational axis, and the particulars of this precession can be altered by internal forces, but the body's angular momentum is conserved. The media appears to prefer ambiguous and simplistic arguments over accuracy however.

Good to see that episode 2 will be on HD on Fri23Mar12. I feared that the Ö÷²¥´óÐã would be unable to find space on the HD channel for this as there was no indication of the HD broadcast on the episode 2 page for a long time. It amazed me that Ö÷²¥´óÐã go to the effort and expense of producing HD programmes, but can not find the space for them! This adds to my frustration of the reduced quality of HD picture on Ö÷²¥´óÐã due to over-compression of the broadcast. I am reduced to being thankful for what I get1

When will episode 3 be broadcast in HD?

To Aira Idris
Thanks for your response to my comment.
However you haven't dealt with the point I made which agreed that whilst Arctic ice cover is declining, Antarctic ice is increasing.
Also that average global temperatures have been static for the last 14 years whereas CO2 has continued to rise.
Therefore the Climate models you mention, and upon which the IPCC rely, are incorrectly programmed and useless.
Apart from these incorrect computerised climate models, there is absolutely no empirical evidence that man's activity (additional CO2) has any effect at all on climate.

The explanation given for ice ages and warm periods was naive and wrong since it ignored feedback effects which are chiefly responsible for the changes. What happens is this. Ice ages and warm periods form an oscillating system. The ice recedes Northwards (warm periods) then something - orbit change, volcanic dust causing cooling etc - starts the ice sweeping S (this takes thousands of years but in geological timescales this is rapid). As it sweeps S it engulfs vegetation, this traps carbon under the ice and removes CO2 from the atmosphere reducing global warming also the increased reflection of the increasing ice gives another feedback. The ice sweeps S until it reaches its southern limit, where the suns radiation keeps it warm enough for the ice to extend no further. It pauses here (ice age) until some unusual warming - orbit change or possibly a belch of CO2 - causes the ice to start melting. But by this time the vegetation under the ice will have turned to methane, a strong GHG this combined with the reduced reflexivity of the melted ice provide the opposite feedbacks causing the ice to sweep back northwards giving us a warm period.
Now man-made global warming is causing the ice to recede further than normal and threatening a drastic further methane release and catastrophic global warming.

Thanks for responding. I'm not totally convinced your explanantion isn't just some post-realisation rationalisation however. I can see that some of my comments have been quite negative, and that you've had plenty of others posting positive comments, so your program appears to have been popular. I just ask that so as to avoid turning off viewers like me, and misinforming others, you take care with the 'sciencey bits'. Thanks.