Greenhouse gasses and heat-island phenomenon as factors for extreme weather events

In recent years, global warming has frequently drawn attention as a major issue. In fact, according to the meteorological records, comparing the annual mean temperature during the period between 1900 and 1929 with 2018, rises of 0.7 degrees Celsius in the world, 1.2 degrees Celsius in Japan, and as high as 3 degrees Celsius in Tokyo have observed.

While you may think a rise of three degrees Celsius is not a big deal, it means that the temperature of Tokyo hit as high as that of Kagoshima and Miyazaki during a period from 1900 to 1929. The key factors for this are greenhouse gases and the heat-island phenomenon.

The reason why carbon dioxide is called a greenhouse gas is that its increase in the atmosphere results in temperature rise in the Earth like being covered with a blanket, which means the gas contributes to making the Earth like a greenhouse. To be more precise, the balance of incoming and outgoing radiant energy will be shifted.

Substances radiate energy depending on their temperature. When heated by solar energy, the Earth’s surface radiates energy. Although energy is absorbed in the atmosphere, energy exceeding the atmosphere’s energy absorption capacity is emitted to space.

On the other hand, since the atmosphere heated from absorbed energy also radiates energy, the temperatures near the Earth’s surface remain moderately heated.

However, as carbon dioxide increases in the atmosphere, the atmosphere’s energy absorption increases. Therefore, with a decrease in energy being released to space, energy increases, which is radiated by the atmosphere owing to more energy absorption.

As a result, since energy radiated by the atmosphere to the surface increases, the temperatures near the Earth’s surface rise. This contributes to global warming.

By contrast, the heat-island phenomenon occurs in urban areas. There are three factors for this.

First, urban areas have less greenspace covered by plants. Evapotranspiration from plants releases water vapor into the atmosphere. This leads to a cooling-down of the atmosphere from the vaporizing water, which has the same effect as water sprinkling. However, an environment with less plants exhibits this effect to a lesser degree.

Second, urban areas are facing a large amount of anthropogenic heat release by automobiles and air conditioner compressor units.

Furthermore, tall buildings are packed together densely in an urban area. Therefore, the restricted airflow leads to the prevention of heat release.

The annual mean air temperature in Tokyo began to surpass nationwide mean air temperatures starting from around 1945, which coincides with the time when Tokyo transformed into a megacity after the postwar reconstruction period.

While the population has been further concentrated into Tokyo, rural areas have fallen into decline. During the postwar period, as farmland and village forest (Satoyama) land use declined.

These circumstances present significant social issues. However, in fact, they become major issues from the perspective of mitigating global warming and the heat-island phenomenon and circulating energy as well.

Ways to coexist with the various functions of ecosystems

Some people may think that while rural areas become devastated, there is nothing wrong with it because it returns to nature without human land use. However, this is not true.

There is a term called ecosystem functions. That means functions and values are generated by ecosystems, which are the relations between organisms and the surrounding environment. Since people have enjoyed benefits provided from ecosystems, they can be called ecosystem services.

First, people have received provisioning services provided by ecosystems. These services include food, timber, and water resources. These services have been cherished and utilized by people as blessings from nature.

There are cultural services as well. People have learned a variety of things from ecosystems and built a culture. Even today, people can learn its history while utilizing it as part of environmental education and recreational places for hiking, etc.

Additionally, a regulating service is also a significant function provided by ecosystems. For instance, by absorbing carbon dioxide and releasing oxygen, plants in the ecosystem regulate the atomospheric environment, which results in regulating the climate. Also, preventing natural disasters, such as soil erosion and streamflow control, is a function provided by ecosystems. An ecosystem itself lies at the foundation of these ecosystem functions. For example, plants that absorbed carbon dioxide not only store it in their bodies but also accumulate carbon in the soil after withering. The soil forms the sustainable cycle in which dead plants and animals are decomposed by microorganisms to return to the soil and fertilizing the earth where plants are nurtured and animals live. In other words, ecosystems preserve diversified species and populations of organisms to sustain ecosystems.

The cycling ecosystems with these diverse organisms, have not been just utilized by people. In fact, by people adding their own processes to them, the multifaceted functions have been effectively sustained.

For instance, although trees in forests absorb carbon dioxide, absorption rate decreases in an old forest. Utilizing timber after harvesting and afforesting cut-over areas not only form the habitats of diverse organisms but provide benefits in terms of regulating the atmospheric environment.

It is uncertain whether people from the Edo era cultivated village forests with awareness of the multifaceted functions of ecosystems.

However, it is certain that their management methods of village forests and their lifestyle without using fossil fuels contributed to receiving ecosystem services and maintaining the cycle and sustainment of ecosystems. These methods have been lost to us over time.

Disseminating information that helps enhance an understanding towards ecosystems

Of course, my intention is not to say that we need to return to a lifestyle like that of the Edo era, and realistically we cannot do so. Compared with the time back then, the population of Japan has increased severalfold. In order for such a large number of people to live an abundant life, utilizing fossil fuels is efficient.

Yet, it became apparent that owing to the use of fossil fuels, the increase in greenhouse gases causes climate change, and with populations being densely concentrated in urban cities, rural areas have become devastated and the heat-island phenomenon now occurs in cities. It is necessary for us change our social systems.

In order to do so, I believe that we can learn from the lifestyle methods of people who lived when fossil fuels were not being used.

For example, a variety of renewable energy has recently been translated into practical applications which include biomass.

This technology utilizes waste from our daily lives as well as plant and animal remains for the generation of energy. In some ways, it is a traditional method of resource utilization.

In other words, unlike the utilization of solar and wind power, its framework allows people to be incorporated into the cycle and sustainment of ecosystems by utilizing the resources generated by daily lives and ecosystems.

When compared with the time of the Edo era, science and technology have advanced significantly. As a result, systems enabling people to live an abundant life could be developed, and furthermore, it has made us realize that there are flaws in these systems.

In that case, it is possible that the advancement of science and technology could be utilized with the application of wisdom from the time when people coexisted with ecosystems.

To accomplish this, as well as advancing science and technology, it is necessary to create a concept for utilization and new values.

To do so, we are required to once again review the knowledge we lost, and it is our mission, as researchers, to disseminate information to this end.

For example, although people living in an urban area would be strongly opposed to the idea of cutting trees in a park, people would realize ecosystem functions are sustained by appropreately managing the plants if they had an understanding towards the functions of ecosystems.

In the same manner, devastated rural areas will not simply return to nature but lead to a disturbance in the balance of ecosystems.

I would like to disseminate information required for people to think about establishing a new social system by reviewing these facts and creating new values.

* The information contained herein is current as of August 2021.
* The contents of articles on are based on the personal ideas and opinions of the author and do not indicate the official opinion of Meiji University.
* I work to achieve SDGs related to the educational and research themes that I am currently engaged in.

Information noted in the articles and videos, such as positions and affiliations, are current at the time of production.