Buy

Books
Click images for more details

Support

 

Twitter
Recent comments
Recent posts
Currently discussing
Links

A few sites I've stumbled across recently....

Powered by Squarespace

Discussion > What's The Difference Between Measured UHI and Met Office weather forecasts

golf charlie
The problem with humans is that we think that the environment we are living in is how it's always been. My grandchildren think that we've always grown Oil Seed Rape, Maize and other crops that currently maintain British Farming. They think that it only snows a few times each winter. They think all houses have always had central heating. You get the idea.

The fact that climate is constantly changing is an alien one difficult to grasp as it takes decades to become noticable, just as it is difficult to think that the climate at a different time was better for human wellbeing and that higher atmospheric CO2 levels will actually improve things.

Oct 25, 2016 at 9:22 AM | Unregistered CommenterSandyS

Mark Hodgson
I'm no further forward in answering the question on how the two branches of the Met Office can both be correct.

But as you say it's been an interesting discussion, but no-one's view has changed, I'm not sure that Entropic man fully understands what I'm trying to say.

Oct 25, 2016 at 9:26 AM | Unregistered CommenterSandyS

Sandy S at 9.22

+1 from me.

Oct 25, 2016 at 9:38 AM | Unregistered CommenterMark Hodgson

SandyS

influenced by a lifetime spend measuring stuff. Where controlling the environment where the measurement is taken is vitally important to getting repeatable results. Checking the values of voltage and temperature given by equipment sensor were regularly verified against regularly calibrated meters.

Your 9.13am post raises an old complaint.

There are standards for calibration and maintainance for meteorological equipment. Professionally run stations maintain these standards as a matter of course. Structures like the Stevenson screen are a long-standing attempt to standards measurement technique. You may also remember discussions of buckets(insulated or not), engine water intake thermometers and buoys as sea temperature measurement techniques.

The problem with historical measurements is that you cannot go back and repeat them. You are stuck with whatever quality control was in use at the time. A lot of time, effort and thought goes into trying to find and compensate for past distortions and changes.

UHI is only one of them. The biggest correction is for time-of-day. Many of the older stations have temperatures recorded at a time which was convenient rather than standardised.

Even for modern systems there is the problem of control. There are 4000+ stations worldwide. Some are run by professional meteorologists, some by airport employees or others. In Northern Ireland the three airport stations are automatic, one is run by a farmer and the fifth by a DoE depot manager.

Whether you are the Met Office, NOAA or the Japanese weather service you get data from these stations, but are dependant on their qualty control.

I can understand your unease. You are used to operating under laboratory conditions, able to control environment, equipment and procedures to the limits of your technology. Unfortunately the metrology of meteorology takes place in the field, the object you are trying to measure is 8000 miles across and highly variable in time and space. Conditions are much less favourable for precise and repeatable measurement.

Imagine taking a series of voltage measurements on a circuit board in your laboratory. Now try to repeat the measurements to the same standard on a heaving deck in the rain.

The meteorologists are well aware of the problems.Victor Venema works on these problems professionally.

On his website is an article on this very subject, including proposals for a modern, purpose desgned station network.

As a measurement engineer you might like to discuss the design of a new system with him directly.

Oct 25, 2016 at 10:54 AM | Unregistered CommenterEntropic man

Entropic man
You have explained some my problems with the whole UHI issue very well.

What I had to try and do was simulate worst case environmental operating conditions, and replicate faults in a repeatable way (if that's not tautology). This leads me to be very sceptical of blanket adjustments without knowing a great deal about the data source. As Anthony Watts proved without visiting every station then you cannot be certain of the environment of a station.

Oct 25, 2016 at 12:22 PM | Unregistered CommenterSandyS

SandyS + others

It comes back to a question or query I have raised before.

The simplest assessment of temperature, is frost. Either yes or no, measuring systems not required. British Stately Homes will have Gardeners diaries fot the benefit of the farms and ornamental gardens going back centuries. European Vineyards will also have records.

First frost. Number of nights of frost. Last frost. Centuries of information exists, and none of it has been adjusted.

SandyS, entirely agree about our constantly changing landscape. Whether it is abandoned Highland Crofts/Farms due to harsh agricultural/political/ownership changes, or change from arable to livestock and vice versa due to EEC subsidies.

I have noticed that when a field is arable for more than a few years, barbed wire fences do not get maintained. This changes movement patterns of walkers and their dogs, deer, foxes, badgers etc. Different hedgerows and bits of woodland get exposed to more usage, sometimes for better, sometimes not. When fences are restored for livestock, man and nature adapts again.

Different crops get different fertilisers insecticides and weedkillers etc. Some are more favourable to the habitats of "garden birds", some are more favourable to corvids etc. Nature is very good at adapting. That is how it has always survived.

Oct 25, 2016 at 2:21 PM | Unregistered Commentergolf charlie

Mark Hodgson

Go to the source at the BEST website

In their FAQ section you will find this.

Is the urban heat island (UHI) effect real?

The Urban Heat Island effect is real. Berkeley’s analysis focused on the question of whether this effect biases the global land average. Our UHI paper analyzing this indicates that the urban heat island effect on our global estimate of land temperatures is indistinguishable from zero.

Let's unpack this a little.

"The Urban Heat Island effect is real."

An urban area behaves differently than the rural area around it. On a clear still sunny summer day an urban area will be several degrees warmer than its rural hinterland. There may be other effects. For example, after a prolonged cold spell all that stone and concrete might warm more slowly than the surrounding countryside.These effects are localised, affecting the urban area.

"Our UHI paper analyzing this indicates that the urban heat island effect on our global estimate of land temperatures is indistinguishable from zero."

When they account for all the effects of UHI on the global land temperature average, the UHI produces a change too small to measure.

I have not read the Berkeley UHI paper. Does it say the same thing in greater detail?

Oct 25, 2016 at 5:42 PM | Unregistered CommenterEntropic man

SandyS

Glad to be of help.

Oct 25, 2016 at 5:43 PM | Unregistered CommenterEntropic man

Entropic man
There was irony in my reply as all you did was throw more reasons to be sceptical into the mix. Which helped only in as much as it reinforced my concerns.

Trust us we're doctors doesn't and shouldn't cut any ice.

Oct 25, 2016 at 6:21 PM | Unregistered CommenterSandyS

BEST Lies then?

Oct 25, 2016 at 6:38 PM | Unregistered Commentergolf charlie

EM

I would recommend that you read the paper - I appreciate that we all have other things to do,and constraints on our time, but the paper's not that long (6 tightly typed pages). Among other things it says this:

"We observe the opposite of an urban heating effect over the period 1950 to 2010, with a slope of -0.10 ± 0.24°C/100yr (2σ error) in the Berkeley Earth global land temperature average. The confidence interval is consistent with a zero urban heating effect, and at most a small urban heating effect (less than 0.14°C/100yr, with 95% confidence) on the scale of the observed warming (1.9 ± 0.1°C/100 yr since 1950 in the land average from Figure 5A)."

I must be missing something, because I cannot see how they can say in their questions and answers that "the Urban Heat Island Effect is real" while saying in their paper "We observe the opposite of an urban heating effect over the period 1950 to 2010".

Maybe it's my sceptic paranoia, but what I see here is a desperate attempt to acknowledge the existence of UHI while denying that it has any (or, if you will, any statistically significant) impact on the temperature records.

For instance, as I've pointed out, the paper says "Urban areas are heavily overrepresented in the siting of temperature stations: less than 1% of the globe is urban but 27% of the Global Historical Climatology Network Monthly (GHCN-M) stations are located in cities with a population greater than 50,000."

But it also says "The huge effects seen in prominent locations such as Tokyo have caused concern that the Tavg estimates might be unduly affected by the urban heat effect. It did not have a strong effect on our estimate– which is not surprising given that urban areas are only 0.5% of the land area (according to the MOD500 map)"

So, which is it? 27% or 0.5%. I'm sorry, but for all the academic discipline in the paper, I find it borderline schizophrenic and utterly unconvincing.

Oct 25, 2016 at 8:12 PM | Unregistered CommenterMark Hodgson

You are an engineer and presumably conversant with the physics of energy flows.

UHI increases 1% of the Earth's surface by 1C, mostly because the lower albedo of urban areas causes them to absorb more insolation.

Please explain the physics which, in your opinion, allows this small input of energy to produce a large increase in the global average temperature. Numbers would be nice.

On the basis of the published data and my own calculation it is impossible. You would need far more energy than UHI is actually retaining. You are effectively saying that UHI is creating energy from nowhere.

It is disappointing to see an engineer become a thermodynamics denier.

Oct 25, 2016 at 8:19 PM | Unregistered CommenterEntropic man

Mark Hodgson

I remember that you have "O" Level maths, but presumably no statistics. Permit me to give you a basic lesson.

observed warming (1.9 ± 0.1°C/100 yr since 1950 in the land average

This is the rate of global warming calculated from the 1500 gchn stations, averaged over the last 65 years.

1.9 is the average value. +/-0.1 is the uncertainty. Combine them and the numbers say that there is a 1 in 20 chance that the average is below 1.8C and a 1 in 20 chance that the average is bigger than 2.0C. There is an 18 in 20 chance that the average is between those limits.

urban heating effect over the period 1950 to 2010, with a slope of -0.10 ± 0.24°C/100yr

BEST calculated UHI for all the urban stations as in my Greenwich example and combined them to give the average above.

The average is -0.1 and the uncertainty +/-0.24C. There is a less than 1 in 20 chance that the average is below -0.34C. and a 1 in 20 chance that the average is greater than 0.14C. There is an 18 in 20 chance that the average is between those limits.

Note that they are not saying that the UHI is definitely positive or negative. They are saying that the average is mall enough and the uncertainties are large enough that either is possible. Since local observations usually show a warming effect the best(sorry) interpretation would be that the overall effect of UHI is a warming between 0 and 0.14C

Put the global and UHI figures and you can estimate the maximum likely contribution of UHI to global warming. I'll use the options that give the maximum probable UHI effect.

The low estimate of global land warming is 1.9-01=1.8C. The maximum estimate for UHI is 0.14C.

The maximum % contribution of UHI is 0.14/1.8 *100 = 7.8%.

This is BEST's bottom line. UHI has caused no more than 7.8% of the increase in global land temperature since 1950.

Oct 25, 2016 at 9:28 PM | Unregistered CommenterEntropic man

SandyS

Given the BEST figures I just calculated for Mark Hodgson, I think I can set you a benchmark.

From the BEST figures I calculated the maximum probable contribution from UHI as 7.8% of the global land average.

Global warming, from whatever cause, is increasing the energy content of the climate system (land,ocean,ice and atmosphere by 3* 10^22Joules/year.

The maximum probable contribution from UHI would, if BEST is correct, be 7.8% of 3*10^22. That would be 2.3*10^21 Joules/year. If you can calculate the annual energy contribution of UHI to the system and show that it exceeds 2.3*10^21 Joules/ year, then you have shown that BEST is wrong.

Oct 25, 2016 at 11:46 PM | Unregistered CommenterEntropic man

EM so all those numbers, sums and assumptions give a figure of only 7.8%

You are the maths and statistics expert, you find the mistakes. How much were BEST paid?

In engineering, when something breaks, that apparently couldn't possibly break, according to the calculations, the calculations, numbers, sums and assumptions are the first things scrutinised by independent engineers, possibly acting on behalf of the Police/Crown Prosecution Service etc.

Internal systems of Quality Control in climate science serve no purpose. Peer Review seems the only system involved. When people independent of Climate Science raise queries, they are subjected to abuse, and never thanked or even acknowledged when proven correct.

If Climate Science can't self correct, it is not science. Stating that "our calculations are correct because we can't find a problem" is not science, especially when observations do not match modelled evidence.

Oct 26, 2016 at 12:08 AM | Unregistered Commentergolf charlie

EM

Thank you for the statistics lesson - you have improved my understanding, and I am grateful.

I still remain perplexed, however, by what seems to be a massive contradiction between the two statements:

"Urban areas are heavily overrepresented in the siting of temperature stations: less than 1% of the globe is urban but 27% of the Global Historical Climatology Network Monthly (GHCN-M) stations are located in cities with a population greater than 50,000."

And: "...urban areas are only 0.5% of the land area (according to the MOD500 map)". Or 3% according to that recent study you linked to, or 7%+ in the UK, etc etc. The difference between 0.5% and 3% is a factor of 6. If they calculate that UHI probably contributes 7.8% of measured global warming (I know it's a scientific paper, but why didn't they say that, for the sake of clarity?) then an error factor of 6 would mean that UHI is contributing something approaching half of global warming.

I should also have mentioned that the paper includes references to various papers which try to estimate UHI effect. One of them, coincidentally to the 50% of global warming point) is:

"De Laat and Maurellis used industrial CO2 emissions to classify stations into industrialized and non-industrialized stations. They found a significant increase in average temperature trend for industrialized stations. McKitrick and Micheals found significant correlations between the local trend in gridded averages and a number of social and economic indicators, and estimated one half of the observed global warming trend (over 1980-2002) might be due to these factors "

They go on to dismiss it as wrong, for reasons which, to my simple and non-scientific mind, I found to be reasonably convincing (which is why I haven't previously mentioned it). But if anybody has time, I would appreciate their views. It starts about halfway down the left-hand column on page 2. The link to the paper is here:

http://www.scitechnol.com/2327-4581/2327-4581-1-104.pdf

Oct 26, 2016 at 8:57 AM | Unregistered CommenterMark Hodgson

One lesson is the plasticity of adjustment of temperature reconstructions. Almost anything can be done with them, given the desire. What we have is little help to solving the problem of attribution.
=======================

Oct 26, 2016 at 9:19 AM | Unregistered Commenterkim

Kim. Temperature data that doesn't fit would appear to be brittle. Rather than being smoothly adjusted, older inconvenient reords are smashed, then abruptly replaced. Interestingly the brittleness remains and some records are abruptly replaced many times.

Oct 26, 2016 at 10:29 AM | Unregistered CommenterACK

Heh, ACK, peanut brittle science.

Speaking of attribution, javier, over at Judy's, in a fascinating post and comment thread has expressed one idea that I've been poorly conveying for some time now. If temperature sensitivity to AnthroCO2 is low then it is weak and beneficial. If it is high, our feeble effort has been combatting a large natural cooling. Of course, there is a continuum between the two ends.

And the greening, oh my! Billions of extra bellies fed, if not now, someday, sooner or later.
===============

Oct 26, 2016 at 10:36 AM | Unregistered Commenterkim

If that's not enough to get you to read his thread, at judithcurry.com, then consider this. He is proposing a gradual descent into glaciation starting sometime in the next two millennia.
=======================

Oct 26, 2016 at 10:45 AM | Unregistered Commenterkim

Mark Hodgson

As I said earlier, stations tend to be set up where people are. Over the last 135 years since the first systematic station data was collected a large proportion of the population has been city based, hence the current 37% urban stations.

The problem, recognised by both sceptics and scientists, is that the urban stations tend to overread due to UHI.

That leaves those measuring current and historical global temperatures with a dilemma.

Do they ignore UHI and therefore overread the global average?

Do they correct for UHI, which actually produces lower global averages, and get complaints from sceptics that they are adjusting the figures?

In practice the question has turned out to be moot. Several independent groups have repeated the BEST type of analysis and found that the effect of UHI is small enough that whether you correct or not makes only a small difference.

Be careful that you compare like with like. Industrialised areas and urban areas are not the same.

An industrialised area has steelworks, chemical plants, oil refineries etc. They are burning large amounts of fossil fuels. This produces large amounts of waste heat, pollution and CO2, on top of the warming expected of an urban area.. A nearby station will show large variations, especially due to the waste heat.

An urban area is houses, factories, shops, roads etc. Most of the warming is due to roofs and roads absorbing more sunlight than fields would.

I would not be at all surprised that an area such as Ellesmere Port outside Liverpool would show more warming than Liverpool and that both would show more warming than rural Lancashire.

Another point that you persistently have trouble with is that these urban and industrial areas make up a small proportion of the planet.

Although they show up as warm in the urban station data, their extra heat, once dispersed across the system, makes very little difference to the overall temperature. As far as climate is concerned, the overall temperature is more important.

Imagine SandyS in his laboratory. Switching on his soldering iron makes little difference to the temperature of the building.

Oct 26, 2016 at 10:57 AM | Unregistered CommenterEntropic man

SandyS

"Trust the doctor"

Over at Latimer Alder's thread they are defining a sceptic as one who tests the data before accepting it.

On that basis you score very poorly. Despite your qualifications in engineering and physics you have done nothing to test the data.

Mark Hodgson, despite his lack of qualifications has asked sensible quantitative questions and I have tried to give him sensible quantitative answers. By Latimer Alder's standards he is a better sceptic than you.

Dammit, by Latimer Alder's standards I am a better sceptic than you!

Oct 26, 2016 at 11:07 AM | Unregistered CommenterEntropic man

Kim

He is proposing a gradual descent into glaciation starting sometime in the next two millennia.

He is late. The gradual descent into glaciation started when we dropped off the Holocene Optimum 5000 years ago.

Unfortunately we have overdone the correction. We have warmed past the Holocene Optimum and are zooming out of Pliocene temperatures altogether.

Oct 26, 2016 at 11:22 AM | Unregistered CommenterEntropic man

Then get skeptical about alarmism. Our warming is most likely small and beneficial, our greening is certain and miraculous.
==================

Oct 26, 2016 at 11:22 AM | Unregistered Commenterkim

Well, yes to your point about the Holocene Optimum, but I believe he is proposing an acceleration starting in the next two millennial. You've been confused by the term 'gradual'. Go read his article and the very informative comment thread.
===================

Oct 26, 2016 at 11:24 AM | Unregistered Commenterkim