What is the actual definition of global warming, and how is it measured?

Regarding the calculation of global temperatures:

1. Sums or averages over the individual temperatures in the field are not temperatures. Neither are they proxies for internal energy.

2. Temperatures from a field (individually or averaged) neither drive dynamics nor thermodynamics. Instead dynamics are driven by gradients and differences, in temperatures and other variables.

3. A global spatial average cannot be an index for local conditions, otherwise nonlocal dependence (i.e ”thermodynamics at a distance”) for local conditions would be required.

4. The utility of any global spatial average of the temperature field as an index for global conditions has been presumed but not demonstrated.

5. It is easily demonstrated that different spatial averaging rules over temperatures can have contrary trends in time (i.e. some increase while others decrease in time) when the two fields being compared have range-overlap, as they do in this context. This is demonstrated here in a basic example and subsequently with actual atmospheric temperature-field observations.

6. No ground has been provided for choosing any one such statistic over the rest as the one proper index for global climate.

7. If there are no physical or pragmatic grounds for choosing one over another, and one increases while the others decreases, there is no basis for concluding that the atmosphere as a whole is either warming or cooling.

http://www.uoguelph.ca/~rmckitri/research/globalte...

You are right to be concerned about the concept of "global temperature" because it is meaningless. No physical process is dependent on that figure. You can argue that temperature is not a useful measure of anything anyway. You usually don't suffer too much if you touch a 1000°C spark from a sparkler but you would be seriously injured if you plunged your hand into a 100°C pan of water.

Who was it who pointed out that if you put your head in boiling water and your feet in frozen CO2 that your average temperature would remain the same? So, no problem here then!

Also, once you start averaging averages then you may well have lost the plot. I am reminded of the question about two rival cricketers who played their first match of the season and cricketer A finished with the highest average after both were bowled out. A maintained the lead all season and in the last match he scored more runs than B but B ended up with the higher average!

An engineer would be concerned if his data collection technique had large holes in its coverage or instruments that were not as accurate as possible. Climate science seems to have no such concerns. In fact, there seem to be two teams who work independently. One team collect data and another team plays with the data on their computers. So the people making the pronouncements are remote from the problems with the instrumentation.

Another problem is that to arrive at sensible conclusions we need to know what the data looked like before man came along. Naturally, there were no thermometers then so we have nothing to compare with. Proxies are therefore used. In the case of tree rings if they show what the scientist wants they are used and if they don't then they are not used (Hide the Decline, anyone?). Even using proxies, high and low temperatures on a daily basis are just not available.

An interesting (to me) study would be one that combined the temperature records in various ways to see how big a difference can be caused just by different analysis techniques. I fully expect different techniques to arrive at different "hottest years".

Another interesting study would be to change the temperature stations used in the analysis and see what differences could be manufactured. One year we dropped about 6000 stations if I recall correctly. That has to put a kink in a curve somewhere.

To answer your question, there is no formal definition and it is measured in a quite ad hoc way with little consistency. Still, if you are only prepared to spend a $billion per day you can't expect good data.

The definition was An Alien Organism was protruding out of the earth at one point in a no fly zone. It weakened the ozone just enough in all iced areas to melt all ice during daylight hours since 1977 until it was turned off 11/28/2012. The exact point to only weaken the ozone was made outside of earth's ozone while earth was rotating. Global Warming no longer exists. If your looking at the oceans rising still. A person in Dubois World is paying $10 Billion a year to pour hundreds of Billions of tons of sand into saltwater and that makes all oceans and Rivers tied in with ocean rise over dry land. I now hear in Dubois World that anyone can buy a gold bar out of a vending machine while all ocean's rise. Mike

Notice Trevor's definition: It’s an observed increase in the average global temperature over a period of time.

Notice that his definition includes natural temperature changes. How convenient. That is why it isn't a scientific term. There is no definition because it is gibberish.

It is a political term meant to fool the gullible that any change is from humans.

The IPCC does not define Global Warming but they do have a definition of Climate Change. The definition states in part:

"Climate change refers to a statistically significant variation in either the mean state of the climate or in its variability, persisting for an extended period (typically decades or longer). Climate change may be due to natural internal processes or external forcings, or to persistent anthropogenic changes in the composition of the atmosphere or in land use" http://www.ipcc.ch/ipccreports/tar/wg1/518.htm

Read the definition carefully and you will note that it's only Climate Change if there has been a "statistically significant variation" which even Phil Jones amitted there has NOT been.

Phil Jones admits NO statistically significant warming

http://www.foxnews.com/scitech/2010/02/15/global-w...

So it's all clearly political hype to get more grants and to keep the 30 year man-made Global Warming gravy train rolling down the track.

Phil Jones, is the head of the Climatic Research Unit, so the Guru and High Priest of Global Warming himself has admitted there has been no statistically significant warming. If anyone on the planet would have been aware of statistically significant warming it would have been Phil Jones and he admitted there has been none. (Game Over)

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It's when the globe warms up and it's measured with a Thermommyter.

Hello Snezzy,

Definition of Global Warming

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It’s an observed increase in the average global temperature over a period of time.

It usually refers to changes in the atmospheric temperature and should reference periods of at least 30 years of anomalously warm values when compared to a base period of at least 30 years. For purposes of clarity and to avoid ambiguity a distinction should be made between periods of naturally induced and anthropogenically induced warming.

How is Global Warming Measured?

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With reference to global warming, temperatures are measured as anomalies against a baseline. For example, NASA uses the average global temperature for the period 1951 to 1980 as it’s baseline and expresses temperatures against this, thus a value of 0.6°C means 0.6°C warmer than the 1951-80 average. The NASA baseline is as good as 14.000°C so to convert to absolute temperatures just add 14. Other temperature records use different baselines causing the anomalous values to vary from between records, the absolute values however are consistent (see second graph below).

How are Temperatures Measured?

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The earliest unbroken temperature record dates from 1659 and is known as HadCET (the Central England Temperature record) [1] but it wasn’t until about 1850 that there were sufficient monitoring stations to get a fairly accurate global picture. Data were obtained from observatories, weather stations, botanical gardens, meteorological offices and shipping from all around the world. The data were telegraphed back to the UK and from 1850 onwards those data have been collated into what is today known as the Hadley Centre Climate Research Unit Temperature Record Number 4 (or HadCRUT4 for short) [2].

By 1880 the US had established it’s own global temperature record and it’s maintained these days by NASA, or more specifically the Goddard Institute for Space Studies. This record is known as GISTemp [3].

In the early days there were a few thousand observation stations, by the 1970’s this had grown to nearly 20,000 stations located on every part of the landmass, data from the oceans were comparatively sparse.

In 1979 satellite observations came online and this has the advantage of recording temperatures right across the surface of the planet. Microwave sounding temperature measurements [4] mean that 3D temperatures can be taken – not just on the surface but right through the atmosphere [5].

The pre-satellite records meant there were perhaps as little as a billion datapoints recorded each year, nowadays we can get that much data just by pressing a few buttons on a keyboard.

The ground station-network is still maintained although today there are only about 12,000 such stations.

Data Consistency and Accuracy

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Each observation station has to conform to standards set by the World Meteorological Office, this ensures consistency across the network.

Many readings are now automated thus eliminating human error. All the same, data are homogeneity adjusted in order to standardise the observations and any outliers are eliminated – thus if someone has inadvertently entered 6.2 instead of 2.6 it will be automatically rejected [6].

There are multiple global temperature records that are independently maintained. If errors did slip through then the affected record would differ from the other records and the appropriate corrections could be made. This has happened once before when the UAH record diverged from the other records, the cause turned out to be an incorrect algorithm used to compensate for satellite drift [7].

Data-processing methods are retrospectively applied to the entire temperature record. For example, the parameters for what defines an outlier may be revised, the change would be applied to the entire temperature record so as to maintain consistency. This has led some sceptics to suggest that such modifications have enhanced the warming signature. In reality what the changes have done is to raise historical temperatures ever so slightly (we’re talking thousandths of a degree) and this has marginally reduced the apparent warming signal. The graph below compares the original data (blue) with the revised data (red):

https://www.flickr.com/photos/trevorandclaire/1448...

It’s worth pointing out that one of the primary global temperature records is the Remote Sensing System (RSS) record maintained by Drs Spencer and Christy [8]. Both are climate change sceptics and their record is consistent with all the other records [9]; this rather negates the claim that global warming proponents have manipulated the data to show warming.

Below is a graph showing the RSS observations together with the HadCRUT3 and GISTemp records over the last 30 years. The anomalous values are different as each dataset uses a different base period, what’s important however is that they all show the same magnitude of warming.

https://www.flickr.com/photos/trevorandclaire/1466...

Another interesting issue concerns the campaign launched by Anthony Watts, perhaps the most well known of all climate change sceptics. Watts maintained that global warming didn’t exist and poorly sited weather stations had introduced a warming bias to the record. To this end he recruited a network of volunteers to survey over a thousand surface stations [10]. He analysed the observations and produced his report, which unfortunately for Watts confirmed there was no bias at all, he then tried to ban the publication and use of his own data 11].

Degrees of Accuracy

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We don’t just have a temperature record since the advent of thermometers. Using a variety of reconstructive techniques it’s possible to calculate global temperatures over the last 542 million years. Such techniques include the analysis of fossilised multi-cellular organisms and comparisons of ratios of isotopic elements and compounds found in sedimentary and cryospheric deposits.

In general, the further back we go the less accurate the record becomes. Up to about a million years ago the records are accurate to within 1°C, beyond that there could be a margin of error as much as 2°C. More recently we can be accurate to within about 0.2°C over the last few thousand years and accurate to about 0.01°C for current and recent temperatures.

Further Information

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[1] HadCET: http://www.metoffice.gov.uk/hadobs/hadcet/

[2] HadCRUT: http://www.cru.uea.ac.uk/cru/data/temperature/

[3] GISTemp: http://data.giss.nasa.gov/gistemp/

[4] Advanced MSU’s: http://en.wikipedia.org/wiki/Advanced_Microwave_So...

[5] MSU Data: http://www.ncdc.noaa.gov/temp-and-precip/msu/

by changes cant you see a change in the pattern its unpredictable if you deny it you cant deny there has been changes so you best prepare for the worst its coming

warming over time.

temperatures averaged over tume and many places.

see climate.nasa.gov