What criticism have scientists said about the koppen climate classification system?

Answer 1

One of the most frequently-raised objections concerns the temperate Group C category, regarded by many as overbroad (it includes both Tampa, Florida and Philadelphia, Pennsylvania for example, even using 0 °C (32 °F) as the baseline). In Applied Climatology (first edition published in 1966), John F. Griffiths proposed a new subtropical zone, encompassing those areas with a coldest month of between 6 °C (43 °F) and 18 °C (64 °F), effectively subdividing Group C into two nearly equal parts (his scheme assigns the letter B to the new zone, and identifies dry climates with an additional letter immediately following the temperature-based letter).

Another point of contention involves the dry B climates; the argument here is that their separation by Köppen into only two thermal subsets is inadequate. Those who hold this view (including Griffiths) have suggested that the dry climates be placed on the same temperature continuum as other climates, with the thermal letter being followed by an additional capital letter - Sfor steppe or W (or D) for desert - as applicable (Griffiths also advances an alternate formula for use as an aridity threshold: R = 160 + 9T, with R equalling the threshold, in millimeters of mean annual precipitation, and T denoting the mean annual temperature in degrees Celsius).

A third idea is to create a maritime polar or EMzone within Group E to separate relatively mild marine locations (such as Ushuaia, Argentina and the outer Aleutian Islands) from the colder, continental tundra climates. Specific proposals vary; some advocate setting a coldest-month parameter, such as −7 °C (19 °F), while others support assigning the new designation to areas with an average annual temperature of above 0 °C.

The accuracy of the 10 °C warmest-month line as the start of the polar climates has also been questioned; Otto Nordenskiöld, for example, devised an alternate formula: W = 9 − 0.1 C, with W representing the average temperature of the warmest month and C that of the coldest month, both in degrees Celsius (for instance, if the coldest month averaged −20 °C, a warmest-month average of 11 °C or higher would be necessary to prevent the climate from being polar). This boundary does appear to more closely follow the tree line, or the latitude poleward of which trees cannot grow, than the 10 °C warmest-month isotherm; the former tends to run poleward of the latter near the western margins of the continents, but at a lower latitude in the landmass interiors, the two lines crossing at or near the east coasts of both Asia and North America