I'm not sure scientist's would agree with it being pure guess work about how warm or cold it was prior to thermometers being invented. Give them some credit!
Most of those who call themselves 'climate scientists' dont do any measuring. They dont even get the original results, just processed results. If you know any stats you know how far off the mark 'rounding off' can put you, and these people are making their 'guesses' within these limits of error.
I was a test engineer for 30 years and despite being considered among the best in the world, we could not sensibly estimate results from 50 years ago within the band they are using for a MILLION YEARS.
They estimate temperature by the remains fond there. This is fair enough at say 2deg, but because they use (someone else.s ) processed results they feel they can use .2 of a deg as gospel, so no, I dont believe most of them deserve that credit, well not those I have talked to or read up on.
But it's not about knowing how hot or cold it used to be to within a couple of degrees. Science has proven within reasonable doubt that the earth's temp has altered over millennia. This has had a significant effect on life as far add they can tell.
I'm not some environmentally claiming the world is doomed sometime soon, however if enough people believe that temp change is happening at a rate faster than possibly ever before
aside from say a meteor strike, then surely it's worth trying to look in to avoiding human interference being a significant contributing factor. After all, if in centuries to come it's proven correct and no one bothered to do anything about it then that's rather a shame. If it turns out humans have no control over climate change then we will have lost little or nothing and gained a lot of knowledge along the way.
Now this is the point I am making. They dont. They can come quite close to establishing the average
temp over a period. Now I dont know how short a period, but I doubt that it is less than a hundred or even a few hundred years.
Now as you probably know, an average temp is over 24 hrs for some period. This can go up or down by a small movement on either end. Moving our model to a workable scald (on here) lats call it a week. Week one, the highest day temp is 80deg days are clear and bright, nights are clear and little cloud the temp falls to 15deg in a linear fashion as expected.
Week 2 the same until thursday when it starts getting a little cloud at night but clearing with sun- up.
The cloud holds the night time temperature up by half a Deg for 4 hrs. Without very accurate digital measuring, this week will be as much as a half Deg hotter than the last one just by 'rounding errors'.
Even todays results from satellites are 'processed' (ie rounded out and 'corrected' by a person's eye) before they are passed to places like Hadley. (They NEVER get the raw data, which to be fair to them thay always ask for)
Once they receive them it goes through another set of rounding to plug into their model.
So even with the best will in the world it is not going to be as accurate as the results they put out.
An example of personal experience. 1940's constant measurement was done with paper on a clockwork drum which a pen rested against while it turned.
looking back through a set of them, I found the data off one was consistently higher than the other 4 in the set.
(Dont remember which country, but it was possibly Singapore). So I went to the storeroom and examined the instrument. At some time it had been knocked over and a small buildup of spilled ink from the marking pen had built up at one spot on the drum. I needed a magnifier to find this, but it had the effect of lifting the paper strip up a fraction which when the figure was 'rounded' it moved up one digit.
This recorders results (processed) has for ever been added to the records for that place and time.
These were operated by professional trained RAF personnel. Remember that much of our data until a couple of decades ago came from schools and monks and bases where a person had to put on their coat boots and gloves and go out with a lamp to look at a glass tube and decide where the reading was with a blizzard in their face.
In short, what I am saying is that todays limits are being applied to instruments that can not be that accurate.
BTW, I am all in favour of cleaning up the planet. As I said in another recent thread, Where I grew up I was surrounded by spoil heaps and the air was thick with crap. Now it is a lovely green area with pure fresh air. I gladly give the environmentalists my thanks and support for this.
Dont go getting the idea I am a 'denyer'