# Mean Earth temperature

Hensch
Data for the mean Earth temperatur:
- For example, the average annual temperature for the globe between 1951 and 1980 was around 57.2 degrees Fahrenheit (14 degrees Celsius). (UCAR).
- The global mean surface temperature is 14.46 °C computed from MODIS data (2001-2012).
- Estimated Jan 1951-Dec 1980 global mean temperature (°C) - using air temperature above sea ice: 14.72

The method is described for example Rohde (2013) "Berkeley Earth Temperature Averaging Process". The averaged temperature is the integral of the local temperatures above the surface. There are corrections for
latitude, elevation and “geographic anomaly”. In my opinion air pressure and humidity must also be taken into account. Does this temperature have a physical meaning?

Homework Helper
Gold Member
Your question can be answered in simple terms by a calculation that assumes the sun is a ## T=6000 ## K blackbody, (approximate surface temperature of the sun), and the Earth absorbs (in a very simple model), everything from the sun that is incident on it. The Earth can then, in this simple model, be assumed to be a blackbody of some uniform temperature that radiates according to the Stefan-Boltzmann Law ## M=\sigma T^4 ##. Putting in the Earth to sun distance (using the inverse square law) in the calculation along with the diameter/radius of the sun allows one to compute a temperature ## T ## for the Earth that it will be at in this dynamic equilibrium. The temperature of the Earth is found from this calculation to be somewhere near ## T=295 \, K=22^o \, C ##. More refined calculations can be done, but this is a very interesting result that can be obtained with a very simple and straightforward calculation.

• jim mcnamara
Gold Member
Dearly Missed
Does this temperature have a physical meaning?

That the measurement you cite differs from the simple radiative number Charles Link came up with suggests the atmosphere gets into the picture, as one would expect. It transfers heat from the equator toward the poles. I suppose that's why the 8 degree difference.

Physical meaning ? i don't know what to say.

Interesting though, your sources say mean temperature was cooler 2001-2012 than 1951-1980. In some circles 'them's fightin' words' . .

• Bystander
Homework Helper
Gold Member
Interesting though, your sources say mean temperature was cooler 2001-2012 than 1951-1980. In some circles 'them's fightin' words' . .
+1

Hensch
Your question can be answered in simple terms by a calculation that assumes the sun is a ## T=6000 ## K blackbody, (approximate surface temperature of the sun), and the Earth absorbs (in a very simple model), everything from the sun that is incident on it. The Earth can then, in this simple model, be assumed to be a blackbody of some uniform temperature that radiates according to the Stefan-Boltzmann Law ## M=\sigma T^4 ##. Putting in the Earth to sun distance (using the inverse square law) in the calculation along with the diameter/radius of the sun allows one to compute a temperature ## T ## for the Earth that it will be at in this dynamic equilibrium. The temperature of the Earth is found from this calculation to be somewhere near ## T=295 \, K=22^o \, C ##. More refined calculations can be done, but this is a very interesting result that can be obtained with a very simple and straightforward calculation.
I know these kind of considerations. This calculation assume a uniform distribution of the temperature. For a mean temperature of about 15°C follows an influence of the atmosphere of about 33K. From my point of view, this is wrong, because the temperature of the Earth without the atmosphere is not the -18°C. In the case without an atmosphere there is no reflection on the atmosphere/clouds and the albedo is about 14%.

My question was related to the measured mean temperature.

Mentor
Okay. We are not getting what you want, I assume. So, the alternative is 20 questions.
... do you want a more comprehensive list of datasets based on differing methods of evaluation? If they exist I fail to see what you gain. What are you trying to establish?

The answer is not the "meaning" of arithmetic means - they are a representation of a dataset usually used for comparative operations, often to test/support a hypothesis. Which proposed use you have correctly dismissed as not very appropriate in this case. Help us out here, please.

EDIT - so there is less confusion I am using representation defined as:
Mathematical representation refers to methods to capture an abstract mathematical concept or relationship.

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• jim hardy
klimatos
The National Oceanic and Atmospheric Administration estimates the 2016 (the most recent year available at this writing) mean global surface temperature to have been 14.84°C (58.71°F). There is a 90% probability that the true mean lies within 0.07°C (0.13°F) of this estimated mean. The year 2016 was the warmest year on record, but it must be noted that accurate records for much of the world did not exist until recently.

Homework Helper
Gold Member
But temperatures vary greatly around the world depending on the time of year, ocean and wind currents and weather conditions. Summers tend to be warmer and winters colder. Also, temperatures tend to be higher near the equator and lower near the poles.

• davenn
Gold Member
But temperatures vary greatly around the world depending on the time of year, ocean and wind currents and weather conditions. Summers tend to be warmer and winters colder. Also, temperatures tend to be higher near the equator and lower near the poles.

yes they do, but did you actually read the thread title ? "The mean Earth temperature" takes all your stated things into account to give an end result of a mean/average temperature for the earth

Dave

johnbbahm
I am not sure we could actually state a mean Earth temperature, and have it mean much of anything.
The GISS states in their Q&A that they do not have a standard collection methodology.
https://data.giss.nasa.gov/gistemp/faq/abs_temp.html
""Q. What do we mean by daily mean SAT?
A. Again, there is no universally accepted correct answer. Should we note the temperature every 6 hours and report the mean, should we do it every 2 hours, hourly, have a machine record it every second, or simply take the average of the highest and lowest temperature of the day? On some days the various methods may lead to drastically different results.""
The error from the different collection methods mentioned could be as much as 2 C.
Plant are some of the only honest agents, and the plant hardiness zones have pushed a bit north, so we are warming,
but by how much, may be outside our capability.

Mentor
I am not sure we could actually state a mean Earth temperature, and have it mean much of anything...
The GISS states in their Q&A that they do not have a standard collection methodology.
https://data.giss.nasa.gov/gistemp/faq/abs_temp.html
""Q. What do we mean by daily mean SAT?
A. Again, there is no universally accepted correct answer.
...so we are warming,
but by how much, may be outside our capability.
Note that while different methods are not comparable, you can use individual methods to track changes over time as long as the methods are consistent.

johnbbahm
I understand that each method could show an anomaly change, I take from the GISS statement, that they do
not know which method was used in the collection from the different reporting stations.