A Tale of Two Climatic Changes: Part One

The first of four posts that discuss the differences between the large climatic change that occurred at the end of the last Ice Age and the our current comparably minor ‘climate change’

Key to understanding the posts is Earth’s power balance as presented by Nobel-laureate Dr John Clauser in a video.

It’s uncontentious – even among anthropogenic climate change enthusiasts – that for the last 400,000 years (and longer) Earth has cyclically alternated between colder periods, known as glacials, and warmer periods, such as our current interglacial.

That climate & temperature change has happened and will almost certainly happen in future is a well-established and uncontentious scientific fact.

Far more contentious are the proposed mechanisms whereby a relatively stable glacial climate has repeatedly transitioned into a relatively stable interglacial climate (and vice versa) under a relatively stable power balance and an optimally-functioning cloud thermostat. Some physical process(es) must be violently – and cyclically – destabilizing Earth’s steady-state climate.

Historical power balances can be estimated (interpreted) from reconstructions of Earth surface temperature.

A NASA reconstruction (https://www.e-education.psu.edu/earth103/node/636) of the Earth’s surface temperature reveals that 21,000 years ago:

1) Most of the Earth, e.g. the tropics and Pacific rim, was only a few ºC cooler

2) The Arctic and North Atlantic rim were substantially colder

3) The Antarctic was locally colder, but also locally showing signs of warming up (yellow ovals).

Note that 21 kyr was after the Last Glacial Maximum (26.5 kyr), and towards the end of a period of “ice sheet stability” (26.5 – 19 kyr) that followed. Also note the post-21 kyr warming followed the same pattern of the 1910-1944 and post-1980.

As reported by the IPCC in AR5:

“the most pronounced warming [occurs] in the Arctic during the cold season, followed by North America during the warm season, the North Atlantic Ocean and the tropics.”

The cause of this regional pattern is the subject of the follow-up posts. The Glacial and Interglacial semi-permanent weather systems So why was the North Atlantic so much colder 21 kyr ago?

This Andersen and Borns map (Andersen, B., Borns, H., 1994, The Ice Age World, Oxford University Press. ISBN 978-8200218104) shows that around 21 kyr:

“the low pressure (L) zone along the atmospheric Polar Front in the Atlantic generated strong westerlies which were periodically very cold, particularly during the winter.

A high pressure (H) over the ice sheet generated very strong, dry, cool to cold katabatic winds and easterly anticyclonic winds. The dominance of the two wind systems alternated.”

This cold semi-permanent weather system was paired to a northwards displacement of the Intertropical Convergence Zone (ITCZ) and was therefore also responsible for an increase in precipitation in the Sahara, which around 21 kyr very likely had megalakes, e.g. the African Humid Period, Paleolake Mega-Chad, etc.

At present, Europe’s climate is dominated by the semi-permanent Azores High/Icelandic Low system, which is mainly responsible for Europe’s climate zones. This weather system is for example the reason Scottish and Norwegian tourists can reliably expect to get soaked.

Europe’s current climate zones. Source: NASA/SEDAC (https://sedac.ciesin.columbia.edu/maps/gallery/search?facets=region:europe&facets=theme:climate)

It shows that between 21 kyr and present the change in semi-permanent weather systems has shifted the Netherlandish, German and English climate zone from cold, dry Tundra to warm, wet Temperate (K-G: Cfb = lime green area).

This K-G Cfb Temperate Zone includes such diverse vacation destinations as:

Small systemic temperature and precipitation fluctuations of 1 ºC and 100 mm will therefore not cause a Köppen-Geiger (K-G) reclassification, i.e. will not cause ‘climate change’, in much of Europe.

Part 1 Conclusions:

1) There was a major climate change in Europe between 21 kyr and present as is evidenced by a major shift in regional K-G classes

2) This climate change was caused by a systemic change in the semi-permanent offshore-Europe weather systems

3) The 1910-1944 and post-1980 periods of global warming did not cause a major shift in K-G classes, and thus represent a comparably minor climate change.

But what caused this shift in the semi-permanent weather systems? How was the glacial power density balance disrupted?

The answers are in Post 2.