By Paul Homewood
This paper was published in 2009, but it is still highly relevant:
I have highlighted the key conclusion, that global sea levels fell by between 31 cm and 47 cm between the MWP and LIA.
Although the LIA minimum occurred around 1730 AD, most of the sea level rise since really only began in the late 19thC, or even later as indicated in the tidal gauge records for Brest, one of the longest datasets:
We know that since the late 19thC , sea levels have risen by maybe 25 cm. So Grinsted’s conclusions imply that MWP sea levels were higher than present. HH Lamb came to similar conclusions in the 1970s.
It is worth pointing out that Grinsted’s model is based around two temperature reconstructions:
- Moburg et al (2005), which has a pronounced MWP and LIA
- Jones & Mann (2004), which has much less MWP/LIA amplitude
The Grinsted paper concludes:
We further find that the Moberg et al. (2005) temperature reconstruction is more consistent with observed sea level rise than the Jones and Mann (2004) reconstruction which we conclude does not have a cold enough Little Ice Age.
The model results are also calibrated against reconstructed sea levels using tidal gauges, (see above graph), giving what the authors describe as “good predictive power”.
Whether the world is 2 to 4 degrees warmer than today by 2100, as the authors suggest, is highly debatable!
But what is apparent is that current sea levels are not unprecedented in recent history. Indeed they point that present sea level is within ~20 cm of the highest level for 110 000 years. This is not in any way alarming, given that most of those 110,000 years spanned the last ice age, and that since then global sea levels have been steadily rising.
In 100 years time, we may get back to MWP sea levels.
via NOT A LOT OF PEOPLE KNOW THAT
December 2, 2023 at 06:54AM
Iowa Climate Science Education 