date: Wed, 16 Jan 2008 11:13:44 +0800
from: "Zhongwei Yan" <yzw@tea.ac.cn>
subject: Re: Draft paper on Chinese temperature trends
to: "Phil Jones" <p.jones@uea.ac.uk>

OK, Phil. I got your points. 

Actually, even for Beijing the 'urbanization' bias as infered from my recent study is also quite small comparing with the whole warming trend, 0.1 vs 0.6 C/dec for the last 3 decades. I have no problem with your conclusion in the paper.

Our early analysis (Yan et al 2001 AAS) applied a bias (~0.1C/dec, based on Portman 1993 without rural record comparison) for Beijing during 1961-97, superimposing upon a linear warming of 0.2C/dec. It's a bit bizarre that my current analysis based on updated data (1975-2006) and detailed rural-site comparisons resulted in an almost same estimate for the urbanization effect, while warming goes on with a much stronger rate. 

Keep in touch. Cheers. Zhongwei

----- Original Message ----- 
From: "Phil Jones" <p.jones@uea.ac.uk>
To: "Zhongwei Yan" <yzw@tea.ac.cn>
Sent: Tuesday, January 15, 2008 10:38 PM
Subject: Re: Draft paper on Chinese temperature trends


> 
>  Zhoingwei,
>     You have missed the point of the paper - or you seem to from 
> your statement
>  that it doesn't agree with your Beijing results.  Beijing is just 
> one site !!! What
>  I'm looking at is the effect for the large area - which is what I'm 
> calling CHINA-LI.
>  The whole point in commenting on the other papers (like Ren et al.) is that
>  you can't extrapolate results from one or even a few sites.
> 
>      I know SST doesn't represent land, but it is the only series I can think
>  of that can be guaranteed to be unaffected. Again this is just for China
>  as a whole - and the whole SST area east of China.  I couldn't get 
> Qingxiang Li
>  to say which sites were rural and which urban. A more detailed analysis
>  would look at coastal land sites with coastal SST, but they would 
> be much noisier.
> 
>     Also what matters is that my gridded series (CRUTEM3v for China) looks
>  just like CHINA-LI.
> 
>    I know the reanalysis can't be purified before 1979, unless the 
> assimilation scheme
>  is told the real observations have higher priority. Without higher 
> priority you can't
>  over come the model bias.
> 
>    What could be happening in much of China is that nighttime temps 
> are warming
>  much more than daytime, so any urban effect is reducing the DTR, but only
>  slightly affecting mean T.
> 
>  Cheers
>  Phil
> 
> 
> At 05:11 15/01/2008, you wrote:
>>Hi, Phil,
>>
>>Thanks for informing of the recent analysis. I noted in the paper 
>>that the urbanization effect on the analysis of the average warming 
>>trend over a large area such as China is negligible.
>>
>>It is somehow not encouraging to my recent analysis of a detailed 
>>comparison between Beijing and rural sites temperature series. The 
>>Beijing station moved to a more-urban site in 1981 and back in 1997. 
>>We carefully compared the records during the subperiods around these 
>>years. The results tend to suggest a possibly urbanization-related 
>>trend of about 0.1C/decade. This estimate is very similar to that by 
>>Portman (1993), which we applied in Yan et al 2001 AAS. A paper is 
>>being drafted. I'll check again the results and send to you for 
>>comment a draft when completed.
>>
>>For the large-area mean trend analysis, I'd agree with your results 
>>but just provide some points helping discussion.
>>
>>(1) The SST can hardly represent the land base climate trend, as 
>>there are regional differences and the atmospheric circulation 
>>adjustments to SST do not necessarily lead to the same sign trend 
>>over the adjacent land area.
>>
>>(2) If the basic observations are contaminated by urbanization, I 
>>wonder if the re-analysis data can be purified.
>>
>>Best wishes and later greetings for a happy new year.
>>
>>Zhongwei
>>
>>----- Original Message -----
>>From: "Phil Jones" <p.jones@uea.ac.uk>
>>To: "Yan Zhongwei" <yzw@mail.tea.ac.cn>
>>Sent: Monday, January 14, 2008 10:33 PM
>>Subject: Draft paper on Chinese temperature trends
>>
>>
>> >
>> >>  Dear Zhongwei,
>> >         I have mentioned to you that I've been working on a paper on
>> >  Chinese temperature trends. This partly started because of allegations
>> >  about Jones et al. (1990). This shows, as expected, that these claims
>> >  were groundless.
>> >      Anyway - I'd appreciate if you could have a look at this 
>> draft.  I have
>> >  spelt things out in some detail at times, but I'm expecting if it
>> > is published
>> >  that it will get widely read and all the words dissected.
>> >     I want to make sure I'm referring to most of the Chinese literature
>> >  on urban related warming trends.
>> >     The European examples are just a simple way to illustrate the 
>> difference
>> >  between UHIs and urban-related warming trends, and an excuse to
>> >  reference Luke Howard.
>> >
>> >  Cheers
>> >  Phil
>> >
>> >
>> > Prof. Phil Jones
>> > Climatic Research Unit        Telephone +44 (0) 1603 592090
>> > School of Environmental Sciences    Fax +44 (0) 1603 507784
>> > University of East Anglia
>> > Norwich                          Email    p.jones@uea.ac.uk
>> > NR4 7TJ
>> > UK
>> > 
>> ----------------------------------------------------------------------------
> 
> Prof. Phil Jones
> Climatic Research Unit        Telephone +44 (0) 1603 592090
> School of Environmental Sciences    Fax +44 (0) 1603 507784
> University of East Anglia
> Norwich                          Email    p.jones@uea.ac.uk
> NR4 7TJ
> UK 
> ----------------------------------------------------------------------------
