On Wednesday, 10 April 2019 11:07:39 UTC+1, Norman Lynagh wrote:

One day last week there was an interview on 'Today' with a Professor of
Paleoclimatology, or some such title. She had been carrying out
research into the world's climate the last time the atmospheric
concentration of CO2 exceeded 400 ppm, some 2-3 million years ago. (The
latest Mauna Loa measurement (8th Apr) is 412 ppm and rising at a rate
of 3ppm per year). She stressed that there is a very long time-lag
before the ocean/atmosphere adjusts to such changes. The last time 400
ppm was exceeded there was apparently a lot of greenery in the
Antarctic. As almost a throw-away comment she said that sea levels then
were around 10-20 metres higher than today's sea level. The interviewer
didn't pick up on that comment but I wonder if that is what is already
locked into the system for our grandchildren to deal with. There's
certainly no hint yet that the rate of increase in atmospheric CO2
might slow down any time soon. On the contrary, the rate of increase is
itself increasing. Fascinating and worrying times.

Norman,
I think you are referring to Dame Jane Francis, Director of the British Antarctic Survey, who was Professor of Paleoclimatology at the University of Leeds.

She would have been reporting on a meeting of the RMetSoc which is described in their latest April Newsletter:

" In collaboration with the Grantham Institute, the Society hosted a joint meeting on a geologic epoch 5.3 to 2.6 million years ago - the Pliocene. This era was the last time carbon dioxide concentrations on Earth were as high as today (above 400 ppm). The scientists presenting during this National Meeting looked at the topic from different angles, such as the scientific evidence from sediment records and fossils, and changes in Antarctica and sea level rise. Looking into the past and understanding change is essential to learn about climate change today. The Pliocene provides valuable information about the world we are heading towards.

The event received a wide press coverage, for example through the BBC[1], the Guardian[2] and the Independent[3]. In a Q&A with the Grantham Institute[4], the speaker of the event, Professor Alan M. Haywood, gives more insight into the topic. The presentations of all speakers and a recording of the meeting can be found here[5]."

1. https://www.bbc.co.uk/news/science-e...6HKWVF,38ZNC,1

2. https://www.theguardian.com/science/...6HKWVF,38ZND,1

3. https://www.independent.co.uk/news/s...6HKWVF,38ZNE,1

4. https://www.imperial.ac.uk/news/1907...6HKWVF,38ZNF,1

5. https://www.rmets.org/event/pliocene...6HKWVF,38V8X,1

IMHO, the bottom line is that we are locked into at least 20m sea level rise. The question is how soon it will happen? We know that sea level rise is accelerating and that CO2 is rising far faster than at any time in the past that we know of. So could sea level also rise far faster than at any time in the past?

Well done to Nick Cook for trying to answer that.

On 11/04/2019 22:17, Alastair wrote:
On Wednesday, 10 April 2019 11:07:39 UTC+1, Norman Lynagh wrote:

One day last week there was an interview on 'Today' with a Professor of
Paleoclimatology, or some such title. She had been carrying out
research into the world's climate the last time the atmospheric
concentration of CO2 exceeded 400 ppm, some 2-3 million years ago. (The
latest Mauna Loa measurement (8th Apr) is 412 ppm and rising at a rate
of 3ppm per year). She stressed that there is a very long time-lag
before the ocean/atmosphere adjusts to such changes. The last time 400
ppm was exceeded there was apparently a lot of greenery in the
Antarctic. As almost a throw-away comment she said that sea levels then
were around 10-20 metres higher than today's sea level. The interviewer
didn't pick up on that comment but I wonder if that is what is already
locked into the system for our grandchildren to deal with. There's
certainly no hint yet that the rate of increase in atmospheric CO2
might slow down any time soon. On the contrary, the rate of increase is
itself increasing. Fascinating and worrying times.

Norman,
I think you are referring to Dame Jane Francis, Director of the British Antarctic Survey, who was Professor of Paleoclimatology at the University of Leeds.

She would have been reporting on a meeting of the RMetSoc which is described in their latest April Newsletter:

" In collaboration with the Grantham Institute, the Society hosted a joint meeting on a geologic epoch 5.3 to 2.6 million years ago - the Pliocene. This era was the last time carbon dioxide concentrations on Earth were as high as today (above 400 ppm). The scientists presenting during this National Meeting looked at the topic from different angles, such as the scientific evidence from sediment records and fossils, and changes in Antarctica and sea level rise. Looking into the past and understanding change is essential to learn about climate change today. The Pliocene provides valuable information about the world we are heading towards.

The event received a wide press coverage, for example through the BBC[1], the Guardian[2] and the Independent[3]. In a Q&A with the Grantham Institute[4], the speaker of the event, Professor Alan M. Haywood, gives more insight into the topic. The presentations of all speakers and a recording of the meeting can be found here[5]."

1. https://www.bbc.co.uk/news/science-e...6HKWVF,38ZNC,1

2. https://www.theguardian.com/science/...6HKWVF,38ZND,1

3. https://www.independent.co.uk/news/s...6HKWVF,38ZNE,1

4. https://www.imperial.ac.uk/news/1907...6HKWVF,38ZNF,1

5. https://www.rmets.org/event/pliocene...6HKWVF,38V8X,1

IMHO, the bottom line is that we are locked into at least 20m sea level rise. The question is how soon it will happen? We know that sea level rise is accelerating and that CO2 is rising far faster than at any time in the past that we know of. So could sea level also rise far faster than at any time in the past?

Well done to Nick Cook for trying to answer that.



The science talks series I run
http://diverse.4mg.com/scicaf.htm
the May speaker is a researcher into peat bog pre-history environment
reconstruction.
Probably does not go back far enough but anyone here with a question
relevant to her subject, I could ask.

I was waiting for the next Aviso Jason3 output before posting this on
the SLR thread, but another long delay.
The only other curve-fit I've found is Prof Steven Nerem ,
https://cires.colorado.edu/council-f...r-steven-nerem
but for data only up to year 2017.42.
and
https://www.pnas.org/content/pnas/115/9/2022.full.pdf
In email with him, variability around the curve is much due to changes
in terrestrial water storage.
I make the equation of his quadratic curve, to graphical/pixel resolution.
y= 42.05 + 2.925*x + 0.042* x^2
(y = mm and x = year minus 2005)
I've decided to use his Enso+Pinatubo adjustment plot to modify the
Aviso J1,J2,J3 data 2003 to 2017 and reign-in the otherwise hareing-off
of SLR (like a couple of years ago) now we are well into the next El
Nino for the latest Jason3 data . Maybe the curve type of best fit will
become quadratic rather than indicial.
I'd not considered acceleration.
I'd dismissed linear (acceleration=0) and exponential (rising
acceleration) SLR as worst goodness of fit and cubic (with change of
time index) converged but poor fit and not well-behaved beyond year 2030.
Leaving quadratic (constant acceleration) and indicial (falling
acceleration) with little difference in goodness between them and
applying his "green" correction could well move the curve-form to
quadratic best fit, as well as expected reduction in SLR projection to 2100.
Taking D2y of my non-Nerem-adjusted indicial form , I get acceleration of
0.48 * x ^(-0.425)
(in mm terms where x = year -2000)
for 2018.0 acceleration 0.14
2030 , 0.11
2050, 0.091
2100, 0.068
From the last seven years of the Nerem plot I get his adjusted SLR near
enough
0.5 difference between his curve fit line and the Jason data, so taking
0.5 or the
average of my curve fit and Jason data, hoping not too much self-fulfilling
as only a couple of pixels in it. Adjusting the Jason3 data fully in
line with his
adjusted curve , to the end of his plot so from 2003.0 to 2017.0 and
using the 0.5 factor to adjust the
latest data 2017.0 out to 2018.9 , beyond his plot, until a better
adjustment emerges, possibly involving phase between SST and SLR
Applying to the latest Jason-3 data up to 29 Nov 2018 .
Reduced SLR to 2100 but moved the best fit curve-type to exponential
unfortuately , not the quadratic or indicial.
So I'll change my policy and go for the most conservative rather than
best R^R goodness of fit,
to the least SLR to 2100 , the indicial form.
Y=Aviso structure cm and x=year - 2000
linear
Y = 1.538367 + 0.32577 *x
, R^2 = 0.98385
year Sea Level Rise (cm)
2020 8.053
2050 17.8
2100 34.1

exponential
y= 2.320390 -3.537474 *(1-Exp(0.049866*x))
r*r = 0.991467
year Sea Level Rise (cm)
2020 8.373
2050 41.59
2100 516.8

quadratic
y = 2.440064 +0.136559 *x + 0.007911 *x^2
r*r = 0.991447
year Sea Level Rise (cm)
2020 8.335
2050 29.045
2100 95.205

indicial
y = 2.655903 + 0.054672*x^1.548546
r*r = 0.991309
year Sea Level Rise (cm)
2020 8.311
2050 26.028
2100 71.024 compared to 77.4cm without "Nerem" adjustment
acceleration in mm terms and self-limiting
0.46441 * x^(-0.451454)
2020, 0.12
2030 , 0.1
2050, 0.08
2100, 0.058

As in the title, new record minimum yesterday, by 8,000 sq km, than any
other 11 April of the satellite era, going by Charctic extent algorithm.

On 12/04/2019 15:25, N_Cook wrote:
As in the title, new record minimum yesterday, by 8,000 sq km, than any
other 11 April of the satellite era, going by Charctic extent algorithm.





a new record for any 12 Apr, just, by 3000 sq km