James Sexton recently pointed out on his blog and in a comment to this post at WattsUpWithThat that the data for Envisat had been altered substantially in the last few days.
You can download sea level data for
- Envisat
- Poseidon/Topex
- Jason1
- Jason2
from www.aviso.oceanobs.com/en/news/ocean-indicators/mean-sea-level/products-images/index.html
By chance I had done exactly that last weekend when I was writing to Bill Donovan UK Environment Agency. Bill is responsible for EA guidance for flood and coastal risk management authorities around the UK.
Bill’s advice is that satellites show 3mm/year sea level rise globally, UK is sinking at about 1mm/year, so plan for 4mm/year.
You can judge how reasonable this advice is by looking at the following graph of monthly sea level observations at Newlyn. The lower line is the linear trendline, the upper line is a rise of 4mm/year starting in 1993.
Why 1993? well tradition has it that’s when sea level rise started accelerating – or maybe it’s just that a satellite when up about then.
Why was I looking at Satellite Sea Level Data?
NASA/JPL produced the following graph (which has also featured on WattsUpWithThat) which clearly shows the rate of sea level rise has slowed.
Also the satellites have been in operation for different periods
| Satellite | From | To |
|---|---|---|
| Poseidon/Topex | 1993 | 2005 |
| Jason1 | 2002 | Current |
| Envisat | 2002 | Current |
| Jason2 | 2008 | Current |
It seemed worth while to look at results for periods when 2 or more satellites had been operating at the same time.
Also as I was interested in UK sea levels it seemed to make sense to look at the North Atlantic data, rather than global.
Prior to the recent ‘adjustments’ there was no data for Envisat prior to 2003. Besides altering existing Envisat data the following new data was introduced.
- 64 data points for Envisat in 2002
- 3 data points for Envisat in 2012
- 1 data point for Jason2 in 2012
The following table summaries the comparisons I made using the data downloaded prior to 10 April and on 12 April 2002. In order to compare like with like, when new data extended a period I have added an extra row which gives the value for the new data and the old period.
| Sea Level Rise |
Global
|
North Atlantic
|
||
|---|---|---|---|---|
| mm/year |
10 Apr
|
12 Apr
|
10 Apr
|
12 Apr
|
|
Jason2(overall)
|
1.33
|
1.42
|
1.14
|
1.03
|
|
previous period
|
1.35
|
1.12
|
||
|
Envisat(Jason2 Period)
|
-1.17
|
5.92
|
1.81
|
7.57
|
|
Jason1(Jason2 period)
|
0.81
|
0.81
|
1.18
|
1.18
|
|
Envisat(overall)
|
0.77
|
2.63
|
1.13
|
3.35
|
|
Jason1(Envisat period)
|
2.34
|
2.35
|
0.49
|
0.91
|
|
Envisat(Poseidon/Topex overlap)
|
2.16
|
-0.90
|
1.59
|
0.85
|
|
Poseidon/Topex (Envisat overlap)
|
2.53
|
2.65
|
2.04
|
2.43
|
|
previous period
|
2.53
|
2.06
|
||
|
Jason1(overall)
|
2.56
|
2.56
|
0.91
|
0.91
|
|
Jason1(Poseidon/Topex overlap)
|
3.26
|
3.26
|
3.56
|
3.56
|
|
Poseidon/Topex(Jason1 overlap)
|
2.97
|
2.97
|
3.18
|
3.18
|
|
Poseidon/Topex(overall)
|
3.42
|
3.42
|
3.81
|
3.81
|
|
Poseidon/Topex(1993-1999)
|
3.44
|
3.44
|
5.38
|
5.38
|
|
Poseidon/Topex(1993-2002)
|
3.41
|
3.41
|
4.28
|
4.28
|
|
Poseidon/Topex(Envisat overlap)
|
2.53
|
2.65
|
2.04
|
2.43
|
|
previous period
|
2.53
|
2.06
|
||
- SLR was measured by Posedion/Topex was higher between 1993-1999, this was particularly pronounced in North Atlantic. Note it is commonly reported that temperatures rose up to 1998 but have fallen since.
- SLR has fallen since 1999 and this trend is most pronounced in North Atlantic, where the previous increase was most pronounced.
- As satellite SLR measurements started around 1993 these measurements have been skewed by this short term affect.
- Global rate of SLR is LESS than 3mm/year since 2002.
- Global measurements from Envisat were somewhat out of line with the other satellites but less so in North Atlantic.
- In bring the overall Envisat rate closer to 3mm/year the Envisat rate for the overlap periods is now significantly out of line with the other satellites.
What Are The Corrections?
Below are graphs showing changes made to Envisat data for Global and North Atlantic sea levels between 10 and 12 April 2012.
Note these are NOT graphs of sea level, but changes to sea level data.
All you have to do is lower the past data and raise the more recent and you’ll get a nice increase in the rate of sea level rise!
And The Effect Is?
Well overall the effect has been to change the rate of sea level rise Envisat shows to be similar to that show by Poseidon/Topex.
But when you look at the overlap period there is still a clear difference.
It reminds me of the words of Peter Cook in his judge sketch
he is a man who can not even carry out a simple murder plot without cooking the whole thing up
Could They Be Right?
There has been a dip in sea levels recently. Below is graph of sea level rise around the UK produced by Prof Phillip Woodworth MBE of Proudman Oceanographic Laboratory. There was large dip in sea levels around 1990.
So from 1993 to 2002 the rate of sea level rise was probably about 3mm/year
As they used to say on Rowan and Martin’s Laugh-in
very interesting but stupid
http://www.youtube.com/watch?v=QczyNaIu9Mo
Does this mean that the rate of sea level rise had permanently risen to 3mm/year?
Of course not. Having fallen it was simply bouncing back, only to fall later. Perhaps someone should tell these people about reversion to the mean.
Peter Taylor in his book Chill attributes all of the Global Warming/Climate Change saga to people not being able to tell the difference between
- Trends
- Cycles
- Pulses
If you haven’t already seen it take a look at what Piers Corbyn has to say at EIKE
You can download slides of Piers Corbyn’s presentation
I particularly like page 40 which has a graph of temperature and CO2 over time. People saw a correlation over a short period and assumed it’s going to go on for ever.
You might also like to look at Timo Niroma’s temperature predictions for the next 30 years or so on page 31.
Does Any Of This Matter?
Definitely yes, in the UK at least.
The Environment Agency has seized upon the the rate of sea level rise ‘accelerating’ from 1993 and produced all manner of tables and charts to show that sea level rise will continue to accelerate.
This will make the maintenance of sea walls ‘uneconomic’. Their solution is to knock holes in the sea walls right now! Pretty funny coming from a body responsible for flood defence.
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