## Day Three – AGU

My notes are going to be quick as I’m off in a half hour.

I started off with Henry Diaz (of Hughes and Diaz 1994) presenting on Watching the Wwestern Forests Burn. He said that drought has increased in the American West with drought in the past 5 years being the highest (unprecedented) in the last 50 years. He provided various projections of changes in Lee’s Ferry water flow with increased warming ranging from a decline of about 15% to 50%. He said that ponderosa pine was at risk in its present habitat (although these species have migrated habitats for millenia). He said that people “join us” at CIRMOUNT.

I sat through a couple of presentations on the Sierra Nevadas, home of the bristlecones and foxtails. Roger Bales presented minute details of snow cover by elevation — saying that we don’t know much about mountain water cycles, pointing out how snow pack at different elevations contributed to stream flow by month. He observed that snow pillows were at lower altitudes so far and gave little information on high-altitude snow pack. He was asked about whether tree-ring studies at high altitude would help. He said that he had been asking Malcolm Hughes to carry out such studies ofr over 5 years without any success.

The next presenter talked about lapse rates at Yosemite National Park, which on an annual basis were 6.5 deg C km-1, but varied daily. Melt was sometimes synchronous, sometimes not.

Littell presented results from a large study of Douglas fir in Washington througbh Idaho in different elevations and aspects. He said that “water limits tree growth on all scales from stand to region”. They obtained detailed T and P gridcells and found a positiver correlation to precipitation and negative correlation to temperature. The key variable was soil moisture, especially from the prior year; the surplus water gradient was a key variable.

I then browsed posters for a while. I had a long discussion with Bruce Malamud of King’s College London, who had a poster on fractional processes. His background was theoretical; he’d written a big review paper in Adv in Geophys about 8 years ago; he was very anxious to get practical examples. I’ll follow up with him. Barton of Wright State was hosting the NG poster session and unusually greeted the various people who walked by.

The adjacent poster was by Heidi Kuzma, who was comparing formalisms of various multivariate methods: Neural networks; Support Vector Machines; Kriging; Wiener Filters. The linear algebra formalism for Support Vector Machines (which I’ve not studied) looked identical to Ridge Regression.

I had a long and very pleasant chat with Armin Bunde, who was a coauthor with von Storch in a paper on the persistence properties of various reconstructions. In that paper, they considered MM03 as an alternative reconstruction. I twitted him a little on that. However, I told him that I sometimes felt more like a politician, who liked any citation as long as you spelled the name right. He laughed. He knew Benoit Mandelbrot and had some interesting stories.

I walked by a number of posters on ocean sediments — Thornalley; Jian Yu MD01-2378, SO185-10460 in the China Sea; poster PP1598; 1773 showed tephras MD99-2275. Then some posters on radiocarbon reservoir — 1774 had reservoirs of 1200-2000 years with certain species; he said that freshwater weeds were sometimes problematic as they got old carbon through their roots (I’m wondering here about Quelccaya). Other sediment posters: Some others 1727 had radiolarians from ODP Site 1123; 1732 on the Faroe Islands for 16000 years HM03-13325; 1742 from Indonesia MD98-2165. 1753 was on the Illimanni ice core where the last 5 meters of a 136.5 meter core represented 15,000 years.

I went to some ice core presentations on the new EPICA core; missed most Masson-Delmontte’s presentation. Then Kawamura presented on O2/N2 ratio dating arguing that these ratios represented local insolation not climate and could be used to tune core dating (enhancing connections between Dome Fuji and Vostok cores).

I saw Michael Mann on the street walking to lunch. I felt cheerful and called out ” Hi., Mike”. He walked by stony-faced and silent not looking one inch in either direction.

Wolff presented on interglacials. He observed that each interglacial had its own characteristics in terms of temperature, CO2 evolution. Some interglacials were warmer than the present one (up to 3 deg C.) The relative shortness of interglacials — the Holocene is already longish is something that’s worth writing about.

Then I went to a couple of presentations on the East Asian monsoon. A Chinese author said that the mosoon was very strong from 1948-1966 and weak from 1975-1997. This connected with precipitation records.

Zhao PP34B then said, contra L Thompson, that there was negligible correlation between Dasuopu ice accumulation and the All-India Monsoon (IMR). He attributed the negative trend in Dsuopu accumulation over the last 150 years to a weakening of trade winds and long-term changes in the Hadley and Walker circulation.

I then went to another ice core presentation. Masson-Delmonte presented on dD and excess deutrim d in Greenland cores North GRIP and GRIP. Excess deuterium is the residual from the equation

$d=\delta D-8* \delta O18$

I talked at length off the record with a couple of people. I seem to be controversial in some quarters. I’ll try to get to the Al Gore talk early but it may be hard to get into.

1. James Erlandson
Posted Dec 15, 2006 at 8:17 AM | Permalink

Steve: Could you expand on “off the record?”

2. jae
Posted Dec 15, 2006 at 10:27 AM | Permalink

Littell presented results from a large study of Douglas fir in Washington througbh Idaho in different elevations and aspects. He said that “water limits tree growth on all scales from stand to region”. They obtained detailed T and P gridcells and found a positiver correlation to precipitation and negative correlation to temperature. The key variable was soil moisture, especially from the prior year; the surplus water gradient was a key variable.

Right on. Trees are good precipitation proxies, but lousy temperature proxies. When are the dendroclimatologists going to face up to this problem?

3. Michael Jankowski
Posted Dec 15, 2006 at 10:49 AM | Permalink

I saw Michael Mann on the street walking to lunch. I felt cheerful and called out ” Hi., Mike”. He walked by stony-faced and silent not looking one inch in either direction.

With such a common name, you learn to become numb to hearing “Mike” called out on the streets.

4. John Hekman
Posted Dec 15, 2006 at 11:33 AM | Permalink

Re: #2, Jae

Trees may be good precipitation proxies and bad temperature proxies, but if there is a weak correlation between precip and temp, then over long periods like MWP, LIA and the present warming, shouldn’t trees have at least a little ability to proxy for temps?

Or asked another way, just what is the correlation between precip and temp, if any?

Posted Dec 15, 2006 at 11:40 AM | Permalink

RE: “I saw Michael Mann on the street walking to lunch. I felt cheerful and called out ” Hi., Mike”. He walked by stony-faced and silent not looking one inch in either direction.”

Steve, he hates you. Real hatred. Watch your back.

6. jae
Posted Dec 15, 2006 at 11:45 AM | Permalink

4: John, I don’t know, and I don’t think anyone does.

Posted Dec 15, 2006 at 11:46 AM | Permalink

RE: #4 – In the Western US, precip and temp have poor corelation. That’s because we get a mix of “standard” mid latitude weather, and tropical weather. We get wet – warm, wet – cold, dry – warm, and dry – cold, sometimes in the space of a few days. Even in the “wet” Pacific Northwest there is immense seaonality in precip, summer being the dry season. And no matter where in the Western US, year to year variation in precip can be immense. The general truth is, West of 100 Deg W longitude, moisture determines everything. And in most places besides the immediate coastline, there is never quite enough of it. Any plants that have managed to evolve here have mechanisms for surviving drought, albeit, ones in our wetter locations are quite stressed in their survival mode and die backs are worse in the wetter locations. But the bottom line is, things in the Western US are moisture limited, totally opposite of the Eastern US.

8. John Hekman
Posted Dec 15, 2006 at 12:10 PM | Permalink

re: #7, Steve

That is very informative. It seems like a really good reason why the BCPs are not a temperature proxy. Maybe that point has been made before, but most of the discussions I remember seeing on this question are more complicated.

Has any study shown clearly that BCP growth is related to precip in the West and that precip and temp are uncorrelated? That would be a solid contribution to the controversy over BCPs.

As you point out, the situation in the Eastern U.S. is different. I assume you mean that growth there is more limited by temp and less by precip.

Since the tree ring proxies overall seem to show some MWP, LIA and recent warming (although the divergence problem comes in more recently), there does seem to be some information contained in the tree rings regarding past temps. The real problem is letting the BCPs drive the results.

9. beng
Posted Dec 15, 2006 at 12:11 PM | Permalink

Some interglacials were warmer than the present one (up to 3 deg C.) The relative shortness of interglacials — the Holocene is already longish is something that’s worth writing about.

This has been linked here before, but the below pdf file has an interesting take on the current Holocene and its resemblance to the interglacial ~400 kyr ago (stage 11?).

http://www.climate.unibe.ch/~stocker/papers/broecker06eos.pdf

10. Willis Eschenbach
Posted Dec 15, 2006 at 5:27 PM | Permalink

John H., thank you for your interesting question. You say:

Trees may be good precipitation proxies and bad temperature proxies, but if there is a weak correlation between precip and temp, then over long periods like MWP, LIA and the present warming, shouldn’t trees have at least a little ability to proxy for temps?

Or asked another way, just what is the correlation between precip and temp, if any?

Two problems with that, John.

The first is that the trees respond to both precipitation and temperature. If it is wet, they’ll grow well when it’s a certain temperature, but if it’s dry, they’ll wilt when it’s the same temperature. Since that results in different ring widths, how do you differentiate between the two?

The second is that even if the moisture is constant, tree rings are narrow when it’s cold, wide when it’s just right, and narrow again when it’s too hot. If you have a narrow ring, was it too hot, or too cold?

The correlation between precipitation and temperature is actually a very different question from the question about trees. The global average answer is that overall, as temperature goes up, precipitation can go either way, There is a tiny correlation, but the effect is very slight (correlation = ~0.07) and not statistically significant. In other words, overall they are uncorrelated.

Regionally, the situation looks like this:

Note that in certain areas, like the band 50°-60°S, the correlation is quite strongly positive, while in others, it’s strongly negative.

Locally, it depends on exactly where you are. Some places it rains when it’s hot, and in others, it rains when it’s cold. And in both places, many years are “unusual”.

w.

11. Rick Clark
Posted Dec 16, 2006 at 8:24 AM | Permalink

Michael Mann and his cohorts must feel themselves under siege. Meetings such as the AGU should be their moment of triumph. Instead, they are seeing the foundations of their methods challenged at every poster session and break period. They are not accustomed to this type of confrontation and may react in unpredictable ways.

12. TAC
Posted Dec 18, 2006 at 10:50 AM | Permalink

I found the Union Session (U34B) on ice cores absolutely fascinating. Clearly the science is advancing — isotopic methods; analysis of dust; extraction of gas samples; physical examination; etc. — and it promises to reveal a lot about, well, a bunch of things (maybe). A few of the recent results are easily interpreted — strong orbital signals are visible — but not all results are easily explained. Schilla, for example, showed that records from only a few hundred miles apart (Siple and Taylor domes, Antarctica) exhibit very different isotopic patterns with respect to deuterium and 018. In any case, it is exciting to see 800K-year time series.

13. Mark T
Posted Dec 18, 2006 at 11:58 AM | Permalink

The second is that even if the moisture is constant, tree rings are narrow when it’s cold, wide when it’s just right, and narrow again when it’s too hot. If you have a narrow ring, was it too hot, or too cold?

Additionally, how do you extrapolate tree rings as a proxy to the _entire_ year. In general, the tree rings that are used in proxies have very short growing seasons. Should conditions be juuuuust right for good growing (presumably wider rings) in the proper season, what does that say about the off-season? Nothing, actually.

Mark

14. JP
Posted Dec 18, 2006 at 1:25 PM | Permalink

#7
Steve,
Good point. Imagine if the Rockies were situated East-West instad of North-South. The climate of the US would be totally different. In weather, geography is everything.

15. Mark T
Posted Dec 18, 2006 at 1:37 PM | Permalink

Thankfully, they are not. Otherwise, I’d probably not be running around bragging about all the time I get to ski. 🙂

Mark

Posted Dec 18, 2006 at 2:00 PM | Permalink

RE: #14 – Look at how different things are in Europe, for this reason. Look at this Fall – thus far Europe is having a drought and warm spell. The Euros think the whole world is having the same – they have not heard what a cold fall the Western 2/3 of the US has had.

17. Brooks Hurd
Posted Dec 19, 2006 at 12:31 AM | Permalink

Steve S,

Here on California’s Central Coast the early summer had several hot weeks which received a lot of press coverage. If the press had followed up, they would found that the rest of the summer was cooler than average. It was cool enough that it offset the early summer heat and delayed the grape harvest by more than 3 weeks.

18. Welikerocks
Posted Dec 19, 2006 at 7:49 AM | Permalink

#17 Brooks, same here down south on the coast. We didn’t have much of a summer except for those few weeks. And right now, we are scraping a layer of ice off our windshields in order to use the car in the morning. The mountains above Orange County are snow-capped right now. I supposed that is why Mount Baldy is called Mount Baldy in the first place. Yesterday I could see from the beach Catalina Island perfectly and turn around in the other direction and see snow capped mountains. It was really pretty. Cold-freezing temps in the morning though. Wind is really cold too.

19. Welikerocks
Posted Dec 19, 2006 at 7:54 AM | Permalink

To further elaborate the thermometer on the back porch is saying 0°C and I have to take step-daughter to the beach for surf team practice in about a half hour!

Posted Dec 19, 2006 at 10:17 AM | Permalink

RE: #17 – 18 – Indeed, for most of California, there was winter weather going on through much of the spring. The rains in the northern 2/3 of the state did not really start their annual tapering off until June (normally would be May at the latest). Even early July was chilly and as noted, the late July heat was pretty much it for real summer weather. August brought early autumn like weather (even commented on at the Monterey NWS site at the time). September started cool, got a little of the “normal” September heat right around the equanox (only 3 or 4 days of it) then back to cool. October started out cool, with a wee bit of Indian Summer weather in the mid to late part of the month. Rains started prior to Halloween in the high 30s latitude which is a few weeks earlier than what passes for normal. Indeed, not much of a summer / dry season this year.

RE: #19 – O’Neil and Body Glove are our friends – LOL!

21. Welikerocks
Posted Dec 19, 2006 at 10:29 AM | Permalink

#19 No kidding! LOL Her grandfather laughs because they did not have wet suits when he was the same age. He said they would build fire on the beach (sometimes with a tire!) to keep warm and took turns tending it and surfing. I can’t even stick a toe in when it’s that cold!

22. Steve Bloom
Posted Dec 19, 2006 at 4:54 PM | Permalink

Re #11: Yeah, things are pretty rough between Mike and the AGU these days. To paraphrase Woody Allen (from Annie Hall), lately Mike can hardly ever get published in EOS, it seems like twice a year at the most. OTOH Diane Keaton’s line might be a more accurate reflection of the situation.

23. Posted May 18, 2009 at 1:13 AM | Permalink

I would imagine they probably wax the car in its entirety before it’s sold. this makes it easy for their detail crews to clean it one last time before you drive off, you looking like a million bucks. I agree with the wax method, as years ago, I had a car without working wipers. this worked for all but the heaviest rains.