Excerpts from: W.J. Gibbs, 1987, “Defining Climate”,

Question, Info, Comment etc are from ‘whatisclimate’

• The term ‘weather’ will here be used

to indicate the state of the atmosphere (pressure, temperature, humidity, wind, etc.) over a given locality or region during a given period of time (minutes , hour, day, month, season, year, decades, etc.).

WIC-Question: What to do with a description, which states only four weather features, although one could possibly list a dozen or more, and is silent on who is determining, the locality and time period.

WIC-Comment: The ‘state of the atmosphere’ is not weather. The ‘state of the atmosphere’ may govern the weather together with the ‘global natural system’.

• The term ‘climate’ is used to indicate the

statistical probability of the occurrence of various states of the atmosphere (pressure, temperature, humidity, wind, etc.) over a given locality or region during a given calendar period.

WIC-Comment: It seems Gibbs is trying a trick. Instead of speaking of average weather, he calls it “statistical probability”, which either is based on historical statistic, or assumed average weather conditions; assumed but whom?

• The essential difference between these two

definitions is that weather relates to the state of the atmosphere during one, and only one, specific period, whereas climate relates to the statistical likelihood of occurrences of states of the atmosphere over a specific calendar period. The latter definition assumes no major change of climate such as those, which have occurred on the time-scale of millennia in the past.

WIC-Comment: Any ‘statistical likelihood’ can only be established to certain aspects of “the weather”, or “the state of the atmosphere”, e.g. temperature.

WIC-Question: Why is Gibbs not able to realize that it is impossible to construe an “essential difference”.

Gibbs thereon discusses - inter alias- following points:

• A different WMO/ICSU concept of weather and climate in 1967.
• Methods of statistical analysis to describe climate
• Rainfall distributions, Rainfall time series, and

The following excerpts are from the: Conclusion

There are a number of different interpretations of the word ‘climate’ currently in use within the scientific community, within governmental and non-governmental institutions and among the public at large, and the following are proposed for general adoption:

WIC-Observation: Those questions have been getting worst since W.J. Gibbs published his paper in 1987. Any serious discussion of the two basic terms has practically stopped with issuing the UNFCCC. Where was Dr. Gibbs’ voice when this happened five years later?

• CLIMATE is the statistical probability of the

occurrence of various states of the atmosphere over a given region during a given calendar period;

WIC-Question: What constitutes

• a state of the atmosphere,
• various states of the atmosphere, and

what are ‘statistical probabilities’, of what type, basis, combination, duration, and so on?

• WEATHER is the state of the atmosphere

over one given region during one given period (minute, hour, day, month, season, year, decade, etc.).

WIC-Opinion: Gibbs definition is of little help and neither fits necessarily a layman’s expectation, nor is useful for academic research. The state of the atmosphere can and should be described in physical, dynamical & chemical terms.

It is important to reduce difficulties likely to arise from different notions as to the word ‘climate’.

WIC-Comment: WIC fully agrees.

The constituent bodies of WMO and of other governmental and non-governmental agencies would seem to be the appropriate bodies to take the initiative.

WIC-Comment: WIC fully agrees.