Thursday, November 27, 2008

Lying figures

Eli recently wondered over to Jen's place where she was celebrating New Year's 2272 in Tuvalu with a close friend. Don't ask and Eli won't tell. Tuvalu, of course, is a bunch of reefs and small islands with a maximum height above sea level of about 5 m today. It is a small place and getting smaller as seal levels rise. Tuvalu is really up against it, being in an area of the South Pacific that is experiencing rapid sea level rise as shown in the map to the right from the University of Colorado Sea Level Change site. The data is from the Topex/Poseidon satellite. The green circle is ~Tuvalu

This is an important issue in Australia and New Zealand as the islanders are looking to get off to somewhere else in the neighborhood, and there are lots of the usual suspects furiously blaming the Tuvaluans for Tuvalu's problems. Well suffice it to say that there are barrels of red herrings in the sea, and strawmen on land, but one in particular attracted Eli's attention the claim originating with the dynamic duo of Baliunas and Soon in Pacific Magazine (2002) and trotted out by Janama.

Check the Science
Well, rather than rely on Brown's "sense" of sea level rise, let's check the instruments. As it turns out, estimates of globally averaged sea level rise in the 20th century are irrelevant since Tuvalu's local sea level change is very different from the globally averaged change. There are three estimates of sea level changes for Tuvalu. The first is a satellite record showing that the sea level has actually fallen four inches around Tuvalu since 1993 when the hundred-million dollar international TOPEX/POSEIDON satellite project record began. Second comes from the modern instruments recording tide gauge data since 1978. There the record for Tuvalu shows ups and downs of many inches over periods of years. For example, the strong El Nino of 1997-98 caused the sea level surrounding Tuvalu to drop just over one foot.
Now that looks fairly strong oh bunnies, but, as Eli tells you RTFR and look at the continuation where this riddle will be answered by the Interactive Sea Level Wizard.

The data for Tuvalu, 179 Longitude 8S Latitude, shows that
the 1998 El Nino caused the sea height to fall by lots of centimeters. Eli thought it would be fun to calculate linear fits for different periods starting in 1993. Take a look to the right. The rise is a fall from 1999 to 2002, but after that rapidly settles in at a constant +0.75 cm/yr. Writing in 2002, with a short 8 year record with a huge drop in 1998/99 one could say that the satellite record showed a net drop in sea level. Many have done the same thing with global temperature, starting fits in the extremely warm year of 1998. As tamino says, garbage is forever and Sally delivers nice steaming packages.

23 comments:

Anonymous said...

> Baliunas and Soon in Pacific Magazine (2002)

Yeah... they were in a hurry.

They also don't seem to have any clear understanding of what makes sea level a 'level'. Never mind those local variations -- though being bang in the middle of El Niño Land makes them nice and big --, sooner or later Global Mean Sea Level is going to come for your balls.

Here and here.

:wq

llewelly said...

and there will be another big El Nino - probably by 2015 I would guess. Will Soon and Baliunas still be around to publish papers on the falling local sea level? Making them look silly when the local sea level returns to rising?

Cyberchrome said...

Things I learned today part 1 - a Fellow of the Royal Meterological Society is not necessarily a professional meteorologist. Who knew? Well I've been told that I've worn out my welcome at Watt's place, (and all I did was very politely ask Dr Courtney for the title of his PhD thesis, very touchy these sceptics), so I wander over here and discover that as if a shrinking homeland was not challenge enough, the poor Tuvaluvians have to contend with being overrun by marine mammals!

Al Gore should make a movie.

Kind regards

CyberChrome aka JP.

Anonymous said...

JP is referring to this line:
"It is a small place and getting smaller as seal levels rise."

heh

sam-hec

David B. Benson said...

Eli --- "seal level rises"?

I thought seal counts were in decline.

:-)

Cyberchrome said...

Congrats, over here on Airstrip One a last bastion of civilisation remains the Round Britain Quiz and I humbly propose a festive quiz question....

What links

(a) The Doctorate of Technical Editor of CoalTrans International Richard S Courtney.

(b) The Fellowship of the Royal Meterological Society of private client solicitor Stephen Wilde

(c) The Nobel Peace Laureate claimed by Viscount Monckton of Brenchley

?

Sure this could improved upon, but I am more of a concept than a detail guy...

Anonymous said...

David, the seals are getting taller. Bunnies would notice such things.

arch stanton

guthrie said...

Cyberchrome- the answer would be "Nothing".
As in, they don't exist. From my humble place as a mere journeyman scientist working in a small part of British industry, I tried to find out about Richard Courtney. Certainly I couldn't find anything to demonstrate that he had authored stuff on coal in Kempes engineering yearbook. Moreover, it does not look like he is or even could be appointed a "Member of the British association of Science writers"

So there is a great deal of suspect things about him. Certainly, his actual "About" page makes no mention of a PhD, a DipPhil from Cambridge in no way being anything like a PhD.

Cyberchrome said...

Even the DipPhil thing seems to belong to the set of things that do not belong to a set.

Anonymous said...

With all of the smart, competent women in this country, it is a great mystery that ones like Baliunas and Palin rise to the top.

These people are an embarrassment.

John Mashey said...

1) it is not obvious that Baliunas has risen to the top...

2) As for Sarah Palin, I conjecture there is relatively little mystery:

a) She campaigned for it starting a while back. Recall that Wassila had its own lobbyist in Washington years ago.

b) She charmed Bill Kristol & other Weekly Stanford + national Review folks when their cruise ship visited AK in 2007 ... and the rest is history.

Google: palin kristol cruise juneau

or just read the new Yorker story:
http://www.newyorker.com/reporting/2008/10/27/081027fa_fact_mayer?currentPage=all

c) And for the best stuff, follow www.mudflats.com .

Horatio Algeranon said...

A warming earth,
Some find alarming,
But I find the prospect,
Rather charming...

Tootaloo, Tuvalu!

EliRabett said...

Arrrrrrrrrrrrrrrrrrrrrrrrrrrrrrgh!

Tilo Reber said...

So Eli, you come up with a rate of sea level rise at Tuvalu of about .75 cm/year after 2002. The University of Colorado chart shows a global rate of sea level rise from 1993 to the present as being .32 cm/year. And the rate since 2002 looks to be considerably less than that. In fact, the global rate for the last three years has been slightly down.

http://reallyrealclimate.blogspot.com/2008/06/university-of-colorado-global-sea-level.html

I would be curious to know why you think that there is such a large divergence between global sea level rise and sea level rise at Tuvalu. It seems that if water was rising faster at one place than at another, then over time it would flow from the high to the low.

With regards to the finding the "true trend", of course different time periods are going to show different trends. Why wouldn't they. What I don't understand is why someone would want to say that a 30 year trend is a true trend while a 10 year trend is not. If you take the surface temperature trend for the last 30 years and fit it into a series of 30 year trend lines that cover the last 1000 years, they will be all over the place.

With regard to doing surface temperature trends that start in 1998, this would be a valid point, but immediately after the 1998 El Nino we had a very longe La Nina that had as much or more effect on the trend line as the El Nino. From the 1998 El Nino to the present there have been 7 ENSO events, 4 El Nino's and 3 La Nina's and their effect on the trend line is tiny. Gavin's own ENSO corrections to the HadCrut3 data show that this is the case. So I don't understand why you go on harping about the 1998 starting point.

http://reallyrealclimate.blogspot.com/2008/07/gavin-schmidt-enso-adjustment-for.html

Anonymous said...

"I would be curious to know why you think that there is such a large divergence between global sea level rise and sea level rise at Tuvalu. It seems that if water was rising faster at one place than at another, then over time it would flow from the high to the low."

There are two mechanisms for this:

1) Sea level is a "level", i.e., an equipotential surface of the gravity field, only approximately. Temperature and salinity variations, currents (Coriolis effect), air pressure (inverse barometer effect), wind pile-up and tides all cause deviations, globally up to a metre or so in both directions. Part of it is permanent and called "sea surface topography"; much of it is time variable also on interannual time scales.

Tuvalu is nicely located in the El Niño area so it should be strongly affected by it, on the several decimetre level.

But yes, over time (long enough time, not a few years) communicating vessels should trump this.

2) sea level as monitored by tide gauges is affected by local vertical tectonic motions. Dunno to what extent that affects Tuvalu, but it's certainly a factor in Scandinavia. Satellite altimetry data, from a down-looking altimeter radar on a GPS-positioned satellite like T/P or Jason, is geocentric and not affected by this.

And yes, over time, as sea level rise accelerates as it does (Church and White 2006, e.g.) it will also trump crustal motions in the end.

:wq

Horatio Algeranon said...

Of short-term trends
As means to ends
We've had our fill (and more)...

See-saw "science"

Tilo Reber said...

Anonymous:
"There are two mechanisms for this:"

Okay, since we are dealing with satellite data, we can forget the second mechanism.

"Temperature and salinity variations, currents (Coriolis effect), air pressure (inverse barometer effect), wind pile-up and tides all cause deviations, globally up to a metre or so in both directions."

Yes, I agree. But all of those effects are only capable of producing short term variations in the trend. The longest of them would be a La Nina or an El Nino. Since 2002, all of the La Nina/El Ninos have been less than one year in length. And yet Eli is showing a rising trend of about .75 cm/yr for 6 years from 2002 for Tuvalu. When I look at the global data, I only get .22 cm/year for those same 6 years.

http://reallyrealclimate.blogspot.com/2008/12/sea-level-data-from-2002-through-2007.html

Eli is showing a constant rise in rate at Tuvalu that is more than 3 times the global rate for 6 years. I simply cannot buy your explanation for that. Also, over that time period, I would expect some effect from the high areas flowing to the low areas. And I see no evidence of that happening.

Sorry, I simply cannot accept your explanation.

By the way, a global sea level rise rate of .223 cm/year totals out to about 8.7 inches in a century. Hardly anything to get excited about. Possibly the great great great great grandchildren of the Tuvalu islanders will have to think about moving. Also, since the last ice age, sea levels have risen several hundred meters, so it probably won't be the first time that islanders from some island have had to leave due to rising sea levels.

EliRabett said...

Eli is not showing it, Topex/Poseidon is showing it. Go fight with the satellite friend Tilo. Now the satellite measures the actual sea level rise, not the differential between the local rise and the subsidence of the nearby surface of tidal gauges.

And, btw. the 22 cm rise Tilo calculates assumes there is no acceleration, which there seems to be, so that is another red herring.

Anonymous said...

Tilo,

- Six years is only six years.
- Sea surface disequilibrium is maintained as long as the cause -- see laundry list -- is maintained. For some causes that means permanently: sea surface topography. The water wants to flow back, but doesn't until allowed to.
- Church and White (2006).

Did you know that the Baltic Sea is permanently "tilted" some 30 cm from West to East/North by the salinity gradient caused by the sweet water output of the big rivers? And the Gulf Stream tilts permanently sideways due to Coriolis? This can be measured.

> Sorry, I simply cannot accept your explanation.

I know. Study more.

:wq

Tilo Reber said...

"Now the satellite measures the actual sea level rise, not the differential between the local rise and the subsidence of the nearby surface of tidal gauges."

Yes, Eli, we all know that it's satellite data. Our previous posts should have made that obvious.

And, btw. the 22 cm rise Tilo calculates assumes there is no acceleration, which there seems to be, so that is another red herring.

No Eli, the herring is yours. If there is acceleration, the data certainly doesn't show it. From 2002 to today the rate of sea level rise is lower than what it was from 1993 to 2002. In fact, for the last three years, the global sea level has fallen slightly. But even if we forget the falling rate of sea level rise, and simply use all of the satellite data that we have available, we end up with a rate that gives us about 13 inches over the next 100 years.

Since the interior of Greenland is below sea level due to the pressure of the 2 mile thick ice sheet sitting on top of it, that ice sheet is going to have to go bobsledding up hill if Hansen's fictitious scenario for sea level acceleration is ever going to materialize.

Tilo Reber said...

"Sea surface disequilibrium is maintained as long as the cause -- see laundry list -- is maintained."

None of the elements of your laundry list list covers the problem. Furthermore, throwing a stack of garbage at something is simply handwaving and nothing more. If you think that there is a reason for the disequilibrium, then give it to me. Don't give me a load of crap that it could be.

Also, we are not talking about a simple disequilibrium. We are talking about a divergence that is making that disequilibrium larger every year. .223 cm/year rise as opposed to .75 cm/year rise for the past 6 years. None of your laundry list of excuses fits.

"I know. Study more."

So that I can do the same kind of pretentious hand waving as you?

Barton Paul Levenson said...

Tilo Reber writes:

I would be curious to know why you think that there is such a large divergence between global sea level rise and sea level rise at Tuvalu. It seems that if water was rising faster at one place than at another, then over time it would flow from the high to the low.

Doesn't work that way. Local sea level is affected by the geophysical figure of the Earth, local salinitry and temperature, currents, winds, wave-generating events and local land motions. Sea level rise is very rarely the same in all places, just as sea level is very rarely the same in all places.

With regards to the finding the "true trend", of course different time periods are going to show different trends. Why wouldn't they. What I don't understand is why someone would want to say that a 30 year trend is a true trend while a 10 year trend is not.

Because a "trend" in statistics has to be statistically significant. In general you need 30 years to show a significant climate trend. That's why the World Meteorologial Organization defines climate as mean regional or global weather over a period of thirty years or more.

Anonymous said...

Tilo,

the map is here. It gives local sea level trends over 15 years... 1993-2008. The values are all over the place -- for now. That's natural variability for you; over 15 years it still only represents a few cm when sea surface variability is well known to be in the decimetres. Give it a few more decades and you'll see the global trend come out of it at every location.

In the Pacific, it's mostly temperature variations, currents and winds -- hey, there's a whole science about it, why should I play Google for you.

I don't pretend to know these things. I actually do. So can you if you bother.

:wq