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Geological, archaeological, meteorological and astrophysical data
portend imminent global multi-metre sea-level rise by combined
solar-driven and man-made warming
Roger Higgs, Geoclastica Ltd, UK
Abstract for submission to European Geosciences Union (EGU) General Assembly, April 2023
DRAFT version 2, 5th August 2022
25-2-2023: NOT SUBMITTED. This abstract will be updated and submitted in
late 2023 to the European Geosciences Union (EGU) General Assembly 2024
Worldwide geological and archaeological benchmarks of former sea level (SL) reveal a
post-50AD/pre-600AD (loosely C14-dated) SL rise, variously interpreted as 1 to 3m,
reaching ~1m above today's SL. This is the 'Rottnest' transgression on the 'Fairbridge
curve' of oscillating Holocene SL (dismissed by IPCC). The Rottnest has many other
local names, e.g. Romano-British (copious UK archaeological evidence reviewed by
Cracknell 2005), Dunkirk II (Belgium), Gilbert V (Pacific), St Firmin (France), Wulfert
(USA). Exquisitely dated (by Roman coins, ceramics, dendro) evidence constrains the
Rottnest to ~350-450AD, including: 1) severe Thames-estuary-side erosion of
Londinium's ~270AD city wall; 2) a drain-tunnel through the wall, deliberately plugged
with post-320/pre-400AD pottery and tile, "possibly to prevent water flowing in behind
the Wall as the river level rose” (Willcox in Hill et al. 1980). Brigham (1990) countered
"the river level could hardly have risen almost 2m in half a century”, but Blanchon
(2009) proved 2-3m SL rise in decades in the previous interglacial, MIS5e; 3) the 410-
450AD main exodus to Britain of Anglo-Saxons, evacuating their NW European coastal
'terpen' man-made mud-mound villages.
Only ice-sheet collapse by warming can explain such rapid metre-scale global
transgressions (Blanchon). Indeed, in Rottnest time, Greenland warmed 0.9°C in only
~40y, 370 to 410AD, then cooled 1.8°C in 60y (Agassiz-Renland ice-core proxy, Vinther
et al. 2009). This 410AD hot peak, proven pan-Arctic (McKay and Kaufman 2014 fig2d),
was unsurpassed until after 2000AD (below); it is not seen in Antarctic ice cores.
Both McKay's and Vinther's temperature graphs (1-2000AD, 9700BC-1980AD) closely
mimic solar-magnetic output (e.g. Wu et al. 2018 graph), supporting Svensmark's theory
(dismissed by IPCC). Simple graph-to-graph visual comparison shows that major peaks
and troughs cross-match, revealing a 100-200y temperature lag, e.g. 1) the 450y-long
Little Ice Age cluster of solar- and temperature minima is clearly offset 200y (1260-
1710AD vs 1460-1910); 2) Vinther's 410AD superpeak (above) matches a 310 solar
superpeak, unsurpassed until the late 1900s (below); and 3) his slightly cooler (by 0.1°C)
peak of 1950 (1940-60 average), corresponding to 1930-50 warmth on Greenland coastal
thermometer charts (NASA-GISS homogenized data), matches the slightly weaker solar
peak of 1785 (i.e. time-lag ~165y).
On these same coastal charts (which strongly match supra-ice-sheet GISP2 thermometer
chart, recorded from 1988), smoothed 2005-2022 temperatures are ~0.5°C warmer than
1930-1950 (see also Kobashi et al. 2017 fig1b), i.e. ~0.4°C warmer than 410AD (Rottnest),
i.e. Greenland's ice-collapse threshold is likely re-breached. This 2005-2022 Greenland
(and global) extra warmth is presumably anthropogenic, as the corresponding (time-
lagged) solar output was less than for the 1930-50 warm period.
SL is now rising only ~3mm/y and acceleration since 1800 is trivial (Jevrejeva et al.
2014), i.e. ice collapse has not yet begun (but note reported Greenland-Antarctic glacier
acceleration). A 2m SL rise in the next 100y (cf. Rottnest; contrast IPCC worst-case 1m
by 2100) would require the rate to jump very soon (<20y?) to 2cm/y or more. However,
unlike the RBT, with its intrinsic end-mechanism (cooling by solar decline, above),
anthropogenic warming has no foreseeable end, so the coming SL rise might exceed 5m.
Worse, the 1901-1991 exceptional 130% solar-magnetic surge, to its highest value in
>2,000y (exceeding Rottnest), portends strong additional warming from ~2065 (1901
plus ~165y lag).