On 04/12/2011 23:11, dennis@home wrote:

Tree ring data has no part to play in modelling climate when actual
temperature records are available.

But they are fine to develop data sets that are used to model ancient
records when no direct measurement was available.. even though they
can't do the same for records when direct measurements are available.

You just don't understand do you.

I understand better than you.

As can be seen below you clearly don't.

I can see that if they don't understand why the measured temps disagree
with the ring data there is no reason to assume the temps based on ring
data where there is no direct measurement are correct.

First let me put one thing straight where both you and Terry can't see
the wood for the trees. The measured temperatures do not disagree with
the tree ring data. They are the temperature and it is the tree ring
data that is inaccurate.

Second the specific problem is not that the tree ring data doesn't
provide a good match through the whole of the directly measured
temperature record. For most of that time there is a good fit and it is
only since about 1950 that the divergence has become apparent by which
time CO2 levels in the atmosphere were higher than the had been for
millions of years.

Its quite simple, even you should be able to understand that.

I wish the same was true about you.

Lets try and explain it very slowly for you...

say a ring grows 1 mm in 2009. You measure the temp and get say 5C.

Is this the level of divergence actually found or a figure you have
plucked out of thin air?

Then you find a ring in 1920 and its 1 mm but the temp is say 3C.

Well I wouldn't be able to do that but someone obviously can.

So now you go to 1700 and find a ring that is 1mm and say the temp must
have been 3C.

Pick your tree carefully and you can find an accurate temperature to
compare your data with even in 1700.

You have ignored the 2009 figure because your faulty assumptions say it
can't be true even though they (the 1930 and the 2009 figures) are both
measured and verifiable.

In your world that might be true but in the real world direct
measurement of temperature gives the temperature and if the proxy method
disagrees it is the proxy method that is gives the wrong result.

You ignore it because it means 1700 may have been warmer than you want
it to have been and throw away the data that doesn't agree with what you
want, not because you have proven the data to be invalid.

I am not going to go into the precise way in which tree ring data
translates into temperature not least because I don't know any of the
detail but the direct temperature record trumps the proxy record every time.

--
Roger Chapman