More on the hockey stick

Previous warm periods don't mean we're not responsible for this one

Posted by Andrew Dessler (Guest Contributor) at 5:34 AM on 17 Jun 2008

Read more about: climate | climate change skepticism | climate science | IPCC

For those interested in temperature reconstructions of past climates, in particular the kerfuffle over the hockey stick, I recently found a pretty good website. It contains a load of useful information, some of which I did not know. For example, consider this famous plot from the IPCC's First Assessment Report:

IPCC Ice Age

Skeptics have used this plot to argue that today's warmth cannot be caused by humans because it was warmer one thousand years ago. The website does a good job of laying out the history behind the plot. For example, I learned that:

The graph was created by climatologist Hubert Lamb to show the temperature of Central England over the last 1,100 years. For these purposes, Central England is the triangular area enclosed by Bristol (west), London (east), and the county of Lancashire (north). Everyone agrees that there was a MWP in England and other areas near or in the North Atlantic.

The fact that this is not a global plot greatly undercuts the skeptics' argument. The website also does a good job discussing the rest of the hockey stick controversy.

For those not immersed in the minutia of climate science, the most recent thinking on temperature reconstructions is that it is likely that the last few decades are the warmest of the last thousand years. "Likely" here means about a two out of three chance that this statement is correct, which makes this a highly uncertain statement.

However, it is important to remember that it is well established that the Earth has been much warmer in the past than it is today. For example, 55 million years ago, in the Eocene, the Earth was so warm that it was completely ice free, with crocodiles and ferns and other frost intolerant species living in the Arctic. However, none of that means that the warming we are experiencing today is not caused by humans.

To understand why, imagine that a skeptic's car does not start one day. He or she takes it into the garage and the mechanic informs the skeptic that the problem is a faulty fuel pump. The skeptic objects, however. The last time the car did not start, he or she tells the mechanic, it was the battery. Therefore, it cannot be the fuel pump now. It must be the battery.

That's essentially the argument that they make when they say, "because the Earth was warmer in the past, today's warming cannot be caused by humans." Do yourself a favor and ignore that argument.

For story: More on the hockey stick
7 Comments | Post a Comment

Morning Doc

How have you been? Last I heard you had reprised the "there's only a dozen sceptics in the whole world" comment in a newspaper, a day or two before Marc Morano published a list of thousands.

Ouch. I feel for you, believe me.

Was that the Oregon list (so many of them floating around it's hard to keep track?)

Alright lets get to it. The Lamb graph isn't used by the sceptics I traffic with, except for the purposes of showing the 180 switch on the MWP by the IPCC since their first report came out.
Mostly the guru, Steve Mc, doesn't try to prove or disprove the MWP. Instead he points out that bristlecone and foxtail graphs are not accurate millenial thermometers.
The IPCC is addicted to tree cores because "warmest of the last thousand years" makes for a good headline in the Washington Post.
They use not just MBH98-99, but also Crowley and Lowery 2000 (two bristlecone series, including Almagre); Esper et al 2002 (two foxtail series); Mann and Jones 2003 (Mann's PC1); Rutherford et al 2005 (Mann's PC series flagrantly unamended); Moberg et al 2005 (3 bristlecone series); Hegerl et al (Mann's PC1 and the Esper foxtail average); Osborn and Briffa 2006 (Mann's PC1 and the Esper foxtail average); Juckes 2007 (the two Esper foxtail series in his Union reconstruction).

Which brings me to the reason I am here today to bug you. The new paper by Helliker and Richter Subtropical to boreal convergence of tree-leaf temperatures shows that most if not all of the IPCC's Millenial reconstructions need to be thrown out like yesterday's bathwater. http://www.nature.com/nature/journal/vaop/ncurrent/abs/na ...
The oxygen isotope ratio (18O) of cellulose is thought to provide a record of ambient temperature and relative humidity during periods of carbon assimilation1, 2. Here we introduce a method to resolve tree-canopy leaf temperature with the use of 18O of cellulose in 39 tree species. We show a remarkably constant leaf temperature of 21.4 2.2 °C across 50° of latitude, from subtropical to boreal biomes. This means that when carbon assimilation is maximal, the physiological and morphological properties of tree branches serve to raise leaf temperature above air temperature to a much greater extent in more northern latitudes. A main assumption underlying the use of 18O to reconstruct climate history is that the temperature and relative humidity of an actively photosynthesizing leaf are the same as those of the surrounding air3, 4. Our data are contrary to that assumption and show that plant physiological ecology must be considered when reconstructing climate through isotope analysis.

The sceptic argument regarding the MWP is two fold.

If it happened before without our assistance then the odds of the modern warming happening without our help are improved. Better then the 1 out of 3 chance you give us.
The MWP was a pretty good time to live judging by the monuments and records. Sure humanity was plagued by petty tyrannts and arbitrary rulers, but it was also the time when England introduced the Magna Carta and Parlement. We have both of those still and plenty of guns to fight off the occasional Mugabe or Saddam.

Have a good day Doc.

PS Are you corresponding with Tim Ball, and do you plan to have another, well allright, the first debate sometime?

by James Mayeau at 8:20 AM on 18 Jun 2008

I, Scientist

There are 10 million people in the US (to say nothing of the world) with scientific degrees, and it's safe to say that you will find thousands of them who believe anything. Strangely enough, they don't manage to get much published because the vast majority know nothing about the topic and couldn't write a paper if they tried (they usually don't).

On another note, perhaps someone can point out the AR4 temperature reconstructions that actually use oxygen isotope ratios of wood cellulose. Then we could determine if "most if not all" are affected by the findings of this recent paper.

And if Tim Ball ever manages to find a working phone, I hope Dessler gets the opportunity to ask Canada's first PhD climatologist if he thinks that CO2 levels will "plummet" again like he believes they did in the early '90s.

by cce at 11:24 PM on 18 Jun 2008

cce

to be sure finding thousands of sceptical scientists in America is no big deal.
There must be millions of climate change advocates in the sciences. So where's your list?

The real challenge will be to find scientists sceptical of MMGW among the actual IPCC reviewers. That would be a trick. Working on it.

This is what Jan Esper had to say about trees with self regulated temperature.
"Those paleoclimatology methods for using isotopes in tree rings to reconstruct climate have been validated by observations," says Jan Esper of the Swiss Federal Research Institute in Birmensdorf. "From this perspective, the findings by Helliker and Richter are indeed surprising, as I would have expected a closer association between leaf and surrounding air temperature," he says.
Jan doesn't sound pleased.
If it's any consolation Steve Mc will be out a hobby. You've got to look on the bright side gents.

http://canadafreepress.com/index.php/article/3021
Doc Tim has his own collumn now. Probably has a phone too.

by James Mayeau at 2:21 AM on 19 Jun 2008

Please spare us those BS lists

I could as well produce lists of mathematicians denying HIV/AIDS (e.g. Serge Lang) and even of scientists denying evolution.

Mars J. Pictor Florifulgurator, Western Bavarian Forest.

by 314159265 at 3:35 AM on 19 Jun 2008

I, scientist, you scientist

See, here's the thing. The lists of "skeptical scientists" are, in fact, lists of people who hold scientific degrees. You might find the opinions of thousands of medical doctors, mechanical engineers, and mathematicians to have merit, but I don't. I have a scientific degree. Lot's of people have scientific degrees. My professional opinion on AGW is as worthless as it is on brain surgery or rocket science.

It's telling that of the 31,000 names on the Oregon petition, only 40 of them are climatologists. I'd like to see them identified, so we can determine if they have ever challenged AGW in peer reviewed work. When it comes to that, these "skeptics" hide under rocks. The people who do publish are the same ones we've all come to know and love.

And are you going to tell us which of the reconstructions in AR4 used oxygen isotopes in wood cellulose and thus back up your assertion that "most if not all" will need to be thrown out?

by cce at 10:22 AM on 19 Jun 2008
[ Parent ]

cce

Your being a bit hard on yourself. I checked out your website. There's some good passes in there.

Did you really read through 31,000 names, checking their credentials? (kind of obsessive - but admirable for it's sheer determination)
http://canadafreepress.com/index.php/article/3566
There's a list of scientists identified on that page, to give you a start on your search for peer reviewed papers.

And are you going to tell us which of the reconstructions in AR4 used oxygen isotopes in wood cellulose and thus back up your assertion that "most if not all" will need to be thrown out?

You seem untroubled by the larger implications of the findings by Helliker and Richter.
Trees regulate their own temperature during the growth phase used by dendroclimatology. Reconstructions using tree cores depend on the premise that tree growth is limited by ambiant temperature. Oops.
The question isn't which of the reconstructions in AR4 use oxygen isotopes, the question is which ones use trees. As far as I can tell that would be all of them. I include the "most" in case of the odd ice core, ocean sediment, borehole, reconstruction which might be buried in the spagetti.

by James Mayeau at 5:09 PM on 19 Jun 2008

More flawed skeptic "reasoning".

Trees regulate their own temperature during the growth phase used by dendroclimatology. Reconstructions using tree cores depend on the premise that tree growth is limited by ambiant temperature. Oops.
The question isn't which of the reconstructions in AR4 use oxygen isotopes, the question is which ones use trees.

The reasoning here is completely wrong.

If in fact trees do regulate their own temperature, that means that they must expend more energy when it's colder. To do so, they must burn some of the carbon captured during photosynthesis. That's carbon not available to make cellulose. Therefore, trees will grow more slowly when it's cold, especially if they must expend energy (i.e. burn carbon that would have otherwise been used to grow the trees) for thermoregulation.

by caerbannog at 8:34 PM on 25 Jun 2008

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