Historically, the human idea of climate was focussed on what was important for their own continuous land-based habitation. The average and the extremes of the local living conditions were the prime influence on what human habitation strategies ... like hunting, gathering, agriculture and shelter... could be successful in establishing a sustainable presence. The concept of climate therefore involves the averaged recollection of many years of seasonal variations and the types of environmental conditions that were important for survival.
The state of the earth's biosphere varies cyclically in time and place because of influences on the system by such factors as global location, the configuration of the continents and the energy input from the sun. Evidence as to the state of the biosphere over time can be deduced from geological and palaeontological records as well as from recent human accumulated measurement data. The short-term experience of weather or the long term recollected appreciation of climate is quite subjective for an individual. Consequently the records of scientifically based measurements must be used as the basis of meaningful comparisons. Thus we use the word 'weather' either to describe the subjective experience of a particular local set of biosphere conditions or to state the specific set of local measurable and recordable conditions. ( Subjectively the weather was wet and windy, but scientifically 100mm of rain fell in 2hours and 70Knot gusts were recorded.) On a longer timescale of many years, the word 'climate' can either be used to describe an individual's memories of seasonal weather or to compute the statistics over time of the set of those weather records for the same period. Scientifically, a climate is a set of statistical parameters... like means, standard deviations, maxima and minima... obtained for a specific region over a specified time interval, and supposed to be characteristic of that region. The parameters usually chosen are those which have a significant influence on living things... temperature, humidity, precipitation, insolation, wind velocity, evapotranspiration ratios, and so on...
Descriptions of climate are an attempt to summarize and simplify the varying conditions and interactions of the biosphere elements... water, air, earth and life... and the behaviour of the system in response to both terrestrial and extra-terrestrial inputs. Thus local regions freeze or bake according to the amount of solar energy input... clouds form in the atmosphere according to temperature levels, humidity and condensation nuclei... winds blow or not according to convection, heat differentials and pressure gradients... etc. Whilst the primary driving energy input of the sun is the major influence on local temperatures, never-the-less all the other elements interact to a greater or lesser degree and thereby participate in a very complex system that resists casual attempts at simplification. Most elements of the biosphere interact with every other element in a significant manner... water vaporizes into the air... gases of the air dissolve in the water... the earth outgasses into the water and atmosphere via geothermal vents... biological entities change the gas proportions of the atmosphere and the reflectance of the earth's surface... variations in water and air availabilities change the types of living things that evolve... minerals of the earth dissolve in or crystallize out of the water... etc... etc... The temperature of a local region would be influenced by its latitude, elevation above sea level, patterns of cloud formation, atmospheric dust, geothermal activity, albedo of the terrain surface, general wind strength, to name the most obvious. The biosphere is a fragile and complex interactive system supported on a planet in a cosmic environment of radiation, high energy particles and magnetic fields. Any climatic modelling of that system will need to take all of that complexity into account.
The commonly used classification proposals concentrate on terrestrial parameters and for the main part ignore the underwater environments of the oceans, lakes and rivers. This will presumably be modified as data becomes increasingly available. With the expanding awareness of the ecologies of global life and the advances of measurement technologies, it should become appropriate to describe any portion of the biosphere in terms of its climate. Once timelines of data have been obtained, climate descriptions of underwater regions would be just as appropriate as those for the terrestrial regions.
From the evidence of archaeology, palaeontology and even human historical records, it is clear that the climate is subject to change. If humans choose to live near the possibility of sudden violent natural hazards... volcanic eruptions, tsunami, or earthquakes... they need to plan carefully for the occurrence of such events and not rely on praying to some god or other to give assistance. Similarly, albeit on a longer timescale, when choosing to live in a particular region, there is no guarantee that the climate of that region will remain the same. It may well be necessary to use technology to adapt to the changes or be forced to abandon the region. The attempt by a group of humans, in the early 21st Century, to modify the climate by invoking unenforceable political regulations about the use of the element carbon, was one of the most revealing pointers to the widespread presence of inherent stupidity and greed-based self-interest.