G'day Blacknad,
OK, Climatology 101
Climate and Climate Change Definitions All definitions are my wording but should not be contentious Ice Age (Capital I and Capital A)An extended geological period during which parts of the earth are covered by ice sheets. There have been four of them. Depending on the definition used, the CURRENT Ice Age has been going 40 million years or for less than 3 million years.
Interglacials (Interglacial Periods) A warmer period where most of the ice sheets retreat. About 10% of the current Ice Age consists of interglacial periods. The current one started 11,323 years ago and will last until at least next week.
ice age (Glaciations) The norm for an Ice Age. Ice sheets extend to at least the line of 45 degrees North (well into the US) and into Northern Germany (but some parts of the north were too cold for ice sheets) and snow extends throughout most of Europe and down to Florida for considerable parts of the year.
The Questions Asked Summary: - Ice Age = a geological age
- Glaciations are not global - Ever
- Well, ever is a long time - at least not since the continents were in this rough position
- Glaciations never confined to Europe alone
- This is NOT the warmest period in this Interglacial Period
- Abundant evidence exists that the Little Ice Age, the Bronze Warm Period and the Medieval Warm Period were across the Northen Hemisphere
1 Ice Age I was referring to the geological age of extended period that is an Ice Age. I'm rather precise about the use of this term because almost no one else is. I rarely even use "ice age" because I think it is too confusing.
2 Ice Age extent I think this may actually be referring to a glaciation. They do vary a bit. For instance the last glaciation created a sheet of ice that abruptly ended along a line in the US which was up to 2 kms thick. This doesn't mean there was no ice below this point. Far from it, there was. But because of this, when it warmed this took a while to melt and eventually about 8,000 years ago two huge lakes being inside the melting sheet burst flooding into the North Atlantic. This did send Europe back into a cold period. Estimates vary from about eight years to 800. The 800 has nothing to support it. It is very often quoted as sending the world back into a cool period. The evidence does not support this at all.
3. Glaciation - worldwide? Glaciations are never worldwide. Sydney where I live pretty much stays the same. Oh, we might have to walk out 5 kms further at Bondi beach or lose a bit of waterfront real estate but otherwise the main difference to Australia is that in a Glaciation it becomes instead of mostly desert, mostly forest with places like Alice Springs receiving 70 inches of rain. Glaciations are a Northern Hemisphere condition (unless you go back far enough to the second world Ice Age when all the continents were in quite different locations).
Previous Warm Periods in this Glaciation As to this crap about the Roman Warm Period or the Medieval Warm Perod or the Little Ice Age (actually three distinct periods of cooling lumped together) being only European is just that;
crap. It annoys me because the evidence is discarded or distorted because those that want to say this is the warmest period for thousands of years do not like the inconvenience of having a much warmer period 6,000 years ago, 2 and a bit thousand years ago and only several hundred years ago. How do I know? Because people may not have had themometers and had their local scribe or monk write "Today was really hot - it was 39.72 degrees celcius" Celcius was not yet invented. But what they did have is art and taxation records. If there is a painting that shows a lake frozen that never freezes to day, you can either say the artist was fantasising or that the area was colder then than now. Now multiple that by thousands all around the world (except Australia which was not yet discovered) and this is no longer "anecdotal evidence that is only of local value".
As to the warm periods they were further back in history but there is still art showing snowcapped mountains not snowcapped in Asia for instance. The Chinese kept tax records and these confirm the Medieval Warm Period and the Little Ice Age.
As far as I am concerned this is much better evidence than tree rings that can be read like tarot cards, giving the answer wanted. If you can grow tropical fruit in a currently cold area then it stands to reason that it was warmer then. Either that or they used greenhouses and thus the "greenhouse effect" is much more ancient than currently argued.
Regards
Richard
