[Diggers350] Somerset levels

[Paul Mobbs]

On Sat, 2014-02-08 at 23:22 +0000, greenwomble wrote:
> I wonder if you've had any thoughts on ice ages and if so what are they.

Ice ages are created by the combined effects of: the precession
('wobble') of the Earth's axis, operating on a 25,000 year cycle; and
the eccentricity of the Earth's orbit, operating on a 100,000 year
cycle.

The wobble of the axis changes the position of the equator/tropics and
the arctic circles (also does things like changing the visual position
of the pole star). In the northern hemisphere, as the position of the
arctic wanders around in a circle, it variously distributes the icecap
across either larger parts of Canada, Greenland, Norway or Siberia -- or
somewhere in between, as now. This means that the areas below the arctic
circles experience a freeze or thaw over this 25,000 year cycle.

The effect of the eccentricity of the orbit is to slightly move the
Earth nearer to or further away from the Sun, creating a change in the
level of the solar heat input to the atmosphere. Although, compared to
precession, it's a much weaker effect.

The theoretical combination of these two effects has been confirmed by
the observation of proxy temperature indicators in sediments (oxygen and
other isotope ratios or existence of certain types of pollen/organisms
as a proxy for water temperature). When eccentricity and precession
combine to create the greatest chill you get a "great ice age" -- like
the last one. After that the severity of the ice ages taking place over
each successive 25,000 year period decreases until you get to the next
'great' one 100,000 years later.

10,000 years ago, at the end of the ice age, the land between Norfolk,
the Dogger Bank and the Dutch coast was well above sea level. The melt
since the end of the last ice age has progressively flooded the North
Sea basin, as well as extensive areas of the Channel, Cardigan Bay and
the Irish Sea (taking a lot of prehistoric/Palaeolithic settlements with
them -- did they complain like Somerset farmers?).

Right now global sea level is just below it's cyclical high -- which
took place a few thousand years ago. Historically sea levels have been
higher -- e.g. during the Jurassic era 180 million years ago they were
100-300 metres higher -- but that's only the case when there's no land
mass over one or both poles. With Antarctica over the south pole ice
(and hence large quantities of water) is lifted out of the sea, lowering
global sea levels compared to those of geological history.

As we go through this natural thaw/freeze cycle, global sea levels also
progressively fall as more water is locked-up in ice. From the historic
highs of 5,000 years ago, they should slowly lower over the next 25,000
years -- reconnecting Britain with Europe, which is probably why the
right-wing don't like climate science! ;-)

So where are we now?

Right now the historic cycle means that temperatures should be falling,
and sea level should be falling -- repeating the cycle we have evidence
for going back almost 600,000 years. That's why there was all that fuss
in the 70's about a new 'ice age', because that's when this research
data first came out -- confirming the theoretical model created by
Milankovitch in the 1920s.

What we're actually seeing is the complete opposite -- temperatures and
sea level rising. We're also seeing changes to atmospheric and oceanic
currents/circulations that indicate a major shift in climate. This isn't
a blip, what we're seeing is a systemic change forced by the
interruption of that historic 'natural' cycle. The big question now is
whether we will force the climate into a different 'metastate' -- a
different equilibrium of either hotter/colder/dryer/warmer compared to
today; or whether the current 'Anthropocene' era will be reversible in
10,000 to 50,000 years time when the carbon is taken out of the
atmosphere and temperatures slowly readjust.

>From 5,000 years ago when global sea level was at a maximum, right up
until about 1,000 years ago, the Somerset levels were an inland marsh --
King Alfred hid from the Vikings there 1,150 years ago! Not salt marshes
at such, because freshwater flowing from inland held the salt water to a
zone near the coast. It was a unique natural ecology, seen today only on
large land masses such as Siberia and Canada.

First with falling sea levels, and then with the first attempts at
drainage 750-900 years ago, the Somerset levels (along with the
Lincolnshire/Cambridgeshire fens, the Vale of York and the Fylde coast
of Lancashire) progressively drained, allowing their conversion to farm
land. The problem with draining is that it causes the sediments to
compress, along with the removal of biomass due to farming -- so parts
of Cambridgeshire are now 4 metres below sea level. That means that land
surface on the levels today is lower than a few hundred years ago,
making drainage comparatively harder and more expensive.

You can't stand against the sea -- it's common sense, as demonstrated by
C'nut 1,000 years ago! We could burn an awful lot of money to keep those
areas of farmland, for the benefit of a few landowners, but that's going
to require a huge subsidy from the rest of us. And, given the other
climate adaptations we need to spend that money on (especially
agricultural/land reform) is it worth it? Arguably it would be cheaper
to relocate the people in the levels/fens on the E. coast to somewhere
well above sea level.

This is the problem about the political/media debate on climate change;
it's static. It assumes that society today represents "normality" --
irrespective of the wealth of evidence against that. E.g., if you go to
the top of Dartmoor, or the Pennines, you'll see the remains of Bronze
and Iron Age farms, created during the warm period of that era. Likewise
although we're going to lose a lot of farm land from around the coast
due to sea level rise, but warming temperatures will also make more land
available in the uplands -- albeit on a more Scandinavian model, because
we'll still get cold winters, given Britain's maritime location.

If we observe the past -- not as human recorded history, but as a
collection of natural and archaeological evidence/phenomena -- we can
find many solutions to our current problems; but that same process can
also be highly critical of current practices. So much of the human
psyche is conservative, unable to accept what its 'senses' directly
reveal to it. That ultimately is the problem we face in the Somerset
levels. 


Anyhow, sorry to ramble on. My problem is that I 'see' all this
information as one joined-up continuum, not as discrete 'issue-sized'
parcels. I come from a family of engineers, and my first employment was
in the engineering industry -- to me everything is just one big engine
that invites tinkering!


P.

-- 

"We are not for names, nor men, nor titles of Government,
nor are we for this party nor against the other but we are
for justice and mercy and truth and peace and true freedom,
that these may be exalted in our nation, and that goodness,
righteousness, meekness, temperance, peace and unity with
God, and with one another, that these things may abound."
(Edward Burrough, 1659 - from 'Quaker Faith and Practice')

Paul Mobbs, Mobbs' Environmental Investigations
3 Grosvenor Road, Banbury OX16 5HN, England
tel./fax (+44/0)1295 261864
email - mobbsey at gn.apc.org
website - http://www.fraw.org.uk/mei/index.shtml
public key - http://www.fraw.org.uk/mei/mobbsey_public_key-2013-2.asc
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