Author Topic: Pre 1880 records  (Read 1920 times)

Zovacor

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Pre 1880 records
« on: May 02, 2016, 01:34:44 am »
I read in many places that "reliable records" go back to 1880, and that is the oldest date that is often used when comparing today's climate to a pre-industrial climate. My question is whether pre or post 1880 records are more useful. I could see data since 1880 helping to shore up the dataset that is currently being used, but I could also see value in pre-1880 data to help extend the historical record further into the past. Any thoughts from the scientific team?

Craig

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Re: Pre 1880 records
« Reply #1 on: May 03, 2016, 12:34:38 am »
I won't presume to answer your question, Zovocor, but you may be interested in this short interview http://www.cbc.ca/radio/quirks/quirks-quarks-for-apr-30-2016-1.3559345/priests-and-traders-collected-climate-data-600-years-ago-1.3559425

Quote
Precise collection of data about temperatures and changing climate is mostly a modern practice, as climate scientists seek to better understand the impact of greenhouse gases on global temperature and climate patterns. But the recent discovery of accurate recording of important climate phenomenon, stretching back six centuries is providing a unique and valuable perspective on recent climate change.

Dr. Sapna Sharma, a biologist from York University, and her colleagues, have analysed records kept since the late 15th century by Japanese priests, recording the date on which a particular lake froze; and a second set of records, kept by traders since the 17th century, noting the time ice broke up on a river in Finland.

They found accurate parallels with "proxy" records from tree rings and lake sediments that further confirm Industrial Age climate warming, and recent climate instability.

AvastMH

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Re: Pre 1880 records
« Reply #2 on: May 03, 2016, 11:01:42 am »
Apologies Zovacor - I meant to reply that I have asked for help from Philip Brohan with the answer.  :)

That's interesting information Craig. When I was putting together a talk I discovered that a couple of centuries ago (and more) the big religious houses kept accurate records of the weather to inform planting times for food provision. And that was vital in those days.  :)
« Last Edit: May 03, 2016, 11:11:59 am by AvastMH »

philip.brohan

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Re: Pre 1880 records
« Reply #3 on: May 03, 2016, 12:03:28 pm »
I read in many places that "reliable records" go back to 1880, and that is the oldest date that is often used when comparing today's climate to a pre-industrial climate. My question is whether pre or post 1880 records are more useful. I could see data since 1880 helping to shore up the dataset that is currently being used, but I could also see value in pre-1880 data to help extend the historical record further into the past. Any thoughts from the scientific team?

TL:DR - we need them all, any time, any place.

The question 'which data is most useful?' is very hard to answer - we are building a dataset of fundamental observations which will be used by many people for many purposes. We guarantee that what we are rescuing is useful by choosing ships in times and places where we know there is demand from scientists now, but we try not to focus too much on what the scientists I know want today, we also have an eye on tomorrow's users and their requirements.

The statement 'reliable records go back to 1880' refers to records of global-mean, annual-mean, temperature. (See http://hadobs.metoffice.gov.uk/hadcrut3/diagnostics/comparison.html - most of these start in 1880). This is the highest-profile scientific product made from our observations (and many others) - it's how we track global warming. When we make such products from all the observations we calculate not only our best guess at the answer, but also how uncertain that best guess is - we produce error-bars. But lots of users don't like uncertainty estimates, they say 'just give us the best estimate for times when that estimate can be treated as reliable, so we don't have to worry about the error-bars' and for those people we say 'just use the data after 1880 - there are still uncertainties, but we are pretty confident the best-estimate is not very wrong'.
That means that if we rescue observations after about 1880 they are unlikely to make a large difference in our estimates of global warming, and if we rescue observations from earlier than 1880, they might make a large difference. But in reality it's not a hard cut-off, we want to reduce uncertainties at all times.
Even more important, the global-mean, annual-mean temperature is not the only thing we are interested in. We also need to know the temperature at 11a.m on May 3rd in Tianjin - how has that changed over the last 100+ years? is spring getting earlier in that location? And for this specific question reliable data don't start in 1880 (more like 1960). And there's nothing special about Tianjin, or May 3rd; we need all times, all places, and the wind, pressure, rain, ..., as well as temperature.
So the early data are more useful for global-mean estimates - but the later data are more useful for local weather estimates, we really do need both. Whatever observations we rescue, someone will use them.

AvastMH

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Re: Pre 1880 records
« Reply #4 on: May 03, 2016, 12:50:07 pm »
Thank you Philip  :)

Danny252

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Re: Pre 1880 records
« Reply #5 on: May 04, 2016, 02:50:40 am »
But lots of users don't like uncertainty estimates, they say 'just give us the best estimate for times when that estimate can be treated as reliable, so we don't have to worry about the error-bars' and for those people we say 'just use the data after 1880 - there are still uncertainties, but we are pretty confident the best-estimate is not very wrong'.

Assuming that those users are other scientists, I must admit I find it slightly shocking to hear that they actively avoid the use of error bars! Certainly in my field (astronomy), not using the uncertainties associated with a measurement wouldn't get you very far in your career.

(Of course, the calculation/estimation of uncertainties is difficult for old data in astronomy as well - but you've done that hard bit for them already!)

Zovacor

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Re: Pre 1880 records
« Reply #6 on: May 15, 2016, 01:50:05 am »
Thanks for the detailed answer!

Zovacor

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Re: Pre 1880 records
« Reply #7 on: September 02, 2016, 03:21:57 am »
On a similar vein, I ran across this today.
https://www.wired.com/2016/08/quickly-climate-change-accelerating-167-maps/

Increasing red and decreasing grey.

mapurves

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Re: Pre 1880 records
« Reply #8 on: September 02, 2016, 04:05:35 am »
On a similar vein, I ran across this today.
https://www.wired.com/2016/08/quickly-climate-change-accelerating-167-maps/

Increasing red and decreasing grey.

That is powerful! and scary   :'(

AvastMH

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Re: Pre 1880 records
« Reply #9 on: September 03, 2016, 12:09:40 am »
On a similar vein, I ran across this today.
https://www.wired.com/2016/08/quickly-climate-change-accelerating-167-maps/

Increasing red and decreasing grey.

 :o :o :o
 :-[ :-[ :-[
 :'( :'( :'(

Totally scary  :-X