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[HQR05-01] Global population distribution changes in response to climatic conditions
Keywords:human climate niche, population density, Köppen climate classification, historical changes
Previous research about Human climate niche, which means the climate conditions for human habitation, have been conducted based on the total density(total population under specific climate condition divided by total land area under specific climate conditions). For example, Xu et al(2020) used this total density and estimated human annual temperature niche, showing that human populations have historically remained concentrated in a narrow climate condition.
However, again, this research was based on total density which is calculated from division of total population under specific climate conditions by total land area under specific climate conditions, the human density of each grid cells under specific climate conditions was not evaluated. As for the relations between climate conditions and population density, Blanc et al(2008) analyzed the relations between precipitation and population density in Sub -Saharan Africa, but this research focused on the population density distribution under specific precipitation conditions, and it seems that there is no research which pay attention to climate conditions for each population density classes.
It is important to know the climate conditions of high population density region, considering its high exposure to the natural disasters. So, this research analyzed climate conditions for grids which have relatively high population density in each era and revealed its historical change(850-2000). This research used results from multiple climate models in past 1000 project from CMIP5 PMIP3 as climate data and Historical Database of the Global Environment Population (HYDE)(Klein,2017) as historical population data. This research used Köppen climate classification in order to classify climate conditions.
As a result, this research found that climate conditions for the highest population density class which contains 10% of the whole population have diversified. For example, there is no D classification by Köppen climate classification(subarctic zone) in climate conditions of the highest population density classes which contains 10% of the whole population in each era from 850 to 1700, but D classification accounts for about 20% in area in 1850. Also, Af(Humid tropics) accounts for only tiny proportion of the climate conditions for the highest population density class which contains 10% of the whole population until 1850, but it accounts for about 7-8 percent in area of climate conditions for the highest population density class which contains 10% of the whole population after 1950.
This trend does not change even if the same climate data is used across the era, so this climate diversification in the highest density class in each era is mostly explained by global population distribution change. For example, the reason for the appearance of subarctic zones in climate conditions of the highest population density classes which contains 10% of the whole population in 1850 is not climate conditions of the highest population density classes which contains 10% of the whole population in 1850 was colder than those in 1700, but the highest density class have more grids in colder area such as northern China and Europe than before.
This result will help us to think about how climate have constrained the location where human beings can develop. Although Human climate niche for the whole human beings has not changed a lot, the climate conditions in which people can gather and develop has become wider.
However, again, this research was based on total density which is calculated from division of total population under specific climate conditions by total land area under specific climate conditions, the human density of each grid cells under specific climate conditions was not evaluated. As for the relations between climate conditions and population density, Blanc et al(2008) analyzed the relations between precipitation and population density in Sub -Saharan Africa, but this research focused on the population density distribution under specific precipitation conditions, and it seems that there is no research which pay attention to climate conditions for each population density classes.
It is important to know the climate conditions of high population density region, considering its high exposure to the natural disasters. So, this research analyzed climate conditions for grids which have relatively high population density in each era and revealed its historical change(850-2000). This research used results from multiple climate models in past 1000 project from CMIP5 PMIP3 as climate data and Historical Database of the Global Environment Population (HYDE)(Klein,2017) as historical population data. This research used Köppen climate classification in order to classify climate conditions.
As a result, this research found that climate conditions for the highest population density class which contains 10% of the whole population have diversified. For example, there is no D classification by Köppen climate classification(subarctic zone) in climate conditions of the highest population density classes which contains 10% of the whole population in each era from 850 to 1700, but D classification accounts for about 20% in area in 1850. Also, Af(Humid tropics) accounts for only tiny proportion of the climate conditions for the highest population density class which contains 10% of the whole population until 1850, but it accounts for about 7-8 percent in area of climate conditions for the highest population density class which contains 10% of the whole population after 1950.
This trend does not change even if the same climate data is used across the era, so this climate diversification in the highest density class in each era is mostly explained by global population distribution change. For example, the reason for the appearance of subarctic zones in climate conditions of the highest population density classes which contains 10% of the whole population in 1850 is not climate conditions of the highest population density classes which contains 10% of the whole population in 1850 was colder than those in 1700, but the highest density class have more grids in colder area such as northern China and Europe than before.
This result will help us to think about how climate have constrained the location where human beings can develop. Although Human climate niche for the whole human beings has not changed a lot, the climate conditions in which people can gather and develop has become wider.