Climate change: causes, scientific aspects and consequences on the environment

More and more often there is news of catastrophic natural phenomena caused by global warming, such as droughts, hurricanes and floods, and in recent years public opinion is increasingly sensitive to issues of environmental protection and ecology.

The link between global warming, industrial gas emissions and fossil fuels has been shown for decades, yet governments have only begun to take serious measures in recent years.

If the emissions of polluting gases do not decrease, the average temperature of the planet will rise by 2 degrees Centigrade in the coming decades, and the consequences could be catastrophic.

What is the “climate”?

Before we can tackle the issue of climate change, we need to give a definition to the concept of “climate”.

The climate is the average state of the weather, considered at various levels (local, regional, national, global) over a period of 20 or 30 years.

The planet is divided into several climatic zones, and at each climatic zone there are different temperatures throughout the year, and different types of flora and fauna (such as rain forests, deserts, steppes, etc.).

In the various climatic zones, the climate tends to remain stable over the years; however, seasonal changes occur every year. The climate is determined by various factors, attributable both to human action and to natural elements and phenomena:

  • latitude (the distance from the equator);
  • albedo (the solar radiation reflected by Earth);
  • sea currents;
  • altitude;
  • proximity to large water basins (they mitigate the climate);
  • proximity to the sea (it mitigates the climate);
  • presence of vegetation (which produces oxygen and absorbs carbon dioxide);
  • human activities;
  • greenhouse effect (caused both by men and nature).

The greenhouse effect is the most well-known phenomenon; however it is not only caused by humans, but is also a fundamental natural phenomenon for life on Earth.

What’s the “greenhouse effect”?

The greenhouse effect is a phenomenon that regulates the planetary temperature, which takes place in every planet with an atmosphere.

It is caused by the accumulation of thermal energy coming from the Sun (the solar rays), and part of this energy is held (in the form of heat) by gas, which prevents the heat from dispersing.

In other words, the Sun emits solar rays that warm the Earth, and part of the energy is retained in the atmosphere by some gases, namely methane, carbon dioxide (CO2), ozone and water vapor: these are the so-called “greenhouse gases”.

Without the greenhouse effect the average temperature on Earth would be around 15 degrees below zero, but this phenomenon causes the temperature to be around 18 degrees, favoring the development of life.

Therefore, as a natural phenomenon, the greenhouse effect is not a negative thing.

However, with the advent of industrialization and the increase in human activities, the greenhouse effect was accentuated by other gases released by the industries, leading to an increase in global temperatures.

The use of fossil fuels (coal, gasoline, etc.) has caused not only an exponential increase in carbon dioxide levels, but has contributed to a more general air pollution.

During the 1980s it was discovered which gases cause the natural greenhouse effect, and what negative effects they cause, especially due to the intervention of CFCs (chlorofluorocarbons), that derive from methane and ethane and were used in various types of industries.

CFCs have been banned since 1987 for their prominent role in the thinning of the ozone layer.

The ozone layer is one of the elements that protects the Earth from solar radiation, but the damage caused by chlorofluorocarbons has caused it to weaken, creating the so-called “ozone hole”.

The ozone layer and the “ozone hole”

The “ozone hole” above Antarctica in 2015: the blue colour shows a great reduction of the ozone shield (source: NASA).

As mentioned, ozone is one of the greenhouse gases.

However unlike the others it does not come from the Earth’s surface, but is found in a layer of the atmosphere called “ozone layer” (or “ozone shield”).

Ozone absorbs and retains part of the energy of the Sun’s rays, especially low and high-wave frequency radiations, which are harmful to life because they cause tumors, decrease the photosynthesis capacity of plants (it would endanger harvesting) and are harmful to the eyes.

Therefore the ozone layer is vital for life on Earth, as it protects us from the most harmful solar radiation.

However, the gases emitted by human activities weaken the ozone shield, making the layer thinner in the middle latitudes (the so-called “temperate zone” of the planet, which includes almost all habitable and inhabited areas), and even greatly reducing it above the Poles (the so-called “hole in the ozone”).

The hole in the ozone causes an increase in harmful radiation reaching the Earth’s surface, but also an increase in temperatures, precisely because fewer solar rays are blocked.

This phenomenon is stronger in spring, and is caused by the action of chlorofluorocarbons and their derivatives.

Despite the almost total banning of these harmful chemical compounds since 1987, it will take decades for the ozone layer to return to its starting levels, and since the CFCs have a long chemical life, it is estimated that the restoration of the ozone layer will end around 2060.

The effects of deforestation and intensive agriculture

Not only CFCs and the use of fossil fuels cause temperatures to rise, but deforestation has an impact on climate change as well.

Trees absorb carbon dioxide and convert it into oxygen, which is one of the gases that make up the air we breathe; yet the uncontrolled ongoing deforestation in various parts of the planet (for example in the Amazon) drastically reduces the number of trees and plants, and consequently tons of CO2, which would normally be absorbed and converted, remain in the atmosphere, warming the climate.

In addition to deforestation, intensive agriculture also causes global warming, for two reasons.

The first reason is the use of pesticides that contain polluting chemicals, that contribute to the increase in the greenhouse effect.

The second reason is directly linked to deforestation, as this type of agriculture requires large areas which are obtained by cutting down acres of forest.

Much of intensive agriculture is not intended to feed us directly, but to feed the farm animals that we eat: this has generated many ethical debates against the exploitation of resources for human nutrition.

Has climate change always been caused by mankind?

Our planet has always undergone climate changes, usually generated by the change in the inclination of the Earth’s axis, which causes a different refraction of the solar rays on the planet, with a consequent change in the climate: this happens approximately every 40 thousand years.

Solar activity and volcanic activity also play an important role in climate change.

Low solar activity leads to lower emissions of ultraviolet rays, with a consequent decrease in temperatures.

In large volcanic eruptions the ashes could expand over vast areas, reflecting ultraviolet rays and causing temperatures to drop.

For example, in 1815 the eruption of the Tambora volcano (in Indonesia) covered the highest areas of the earth’s atmosphere with ash; in the following year, on June and July, in the United States and northern Europe (thousands of kilometers away from Indonesia) were recorded cold temperatures, with the presence of snow and ice.

On Earth there have been several ice ages that lasted thousands of years, caused by the periodic inclination of the Earth’s axis, followed by interglacial eras, also lasting thousands of years.

Interestingly, the last ice age began in the early 1300s and ended around 1850, in the midst of the industrial revolution, and it is called “Little ice age” due to its duration of only five centuries.

How was the link between CO2 and global warming discovered?

The “Keeling curve” shows the rise of the CO2 levels between 1958 and 2018: these levels surpassed 400 parts per million, due to the usage of fossil oils (source: Wikimedia Commons).

The phenomenon of global warming was first highlighted in the late nineteenth century by Swedish physicist Svante Arrhenius, who first theorized a possible link between carbon dioxide and global warming.

In the following decades, scientists theorized that the oceans would be able to absorb excess CO2, but these theories were refuted by studies conducted in 1957 by scientists Roger Revelle and Hans Suess on the summit of the Mauna Loa volcano (in the Hawai’i Islands): the two scientists proved that while the oceans are able to absorb CO2, they do it at a much slower rate than previously theorized, and therefore increases in the planet’s temperature could have occurred.

Measurements made during the 1960s and 1970s in the Mauna Loa volcano further confirmed Revelle and Suess’s claims, showing that over the course of twenty years, the levels of carbon dioxide in the atmosphere had indeedincreased.

Scientist Charles David Keeling carried out an analysis about this issue, and elaborated a graph that visually showed the increase of CO2 in the atmosphere (the so-called “Keeling curve”, which is still used nowadays).

What consequences could climate change lead to?

The effects of rising temperatures are already noticeable nowadays, and we already know what the effects will be in the future.

The most widely-known effect is the melting of ice, both at the Poles and on the top of the mountains.

The melting of the polar ice caps would cause not only the extinction of the species that live in the Poles, such as polar bears, but also a general rise in sea level throughout the planet, which will make many areas no longer habitable: one of the direct consequences will be the migration of millions of people from flooded areas to safer places, causing a humanitarian catastrophe.

Rising temperatures will lead to ocean and seas acidification, causing irreparable damage to the marine ecosystem, as a lowering of the water’s pH levels would make life impossible for many marine species: as an example, the Great Barrier Reef would be destroyed.

Another serious consequence desertification, which will lead to heat waves and a fall in crops, generating waves of famine and consequent migration of populations to fertile areas.

There would be a serious loss of biodiversity (both animals and plants), that is the risk of extinction of many life forms, which would have as possible consequences famines and economic crises (due to the disappearance of food products and the subsequent increase in production costs of alternative foods).

Finally, the rise in temperatures would lead to the spread of tropical diseases in temperate areas, such as malaria, due to heat waves.

So far, the planet’s average temperature has risen by 0.8 degrees, and the consequences are already serious.

If the current situation will not change, it is estimated that the average temperature of the planet will rise by 2 degrees by the year 2100.

Possible solutions against global warming

It is possible to limit the damage caused by global warming with specific policies and strategies, but bringing the temperature back to its original state it will take decades, or even centuries.

Among the possible solutions against global warming there is the abandonment of fossil fuels and the subsequent transition to renewable and alternative energy sources.

For many years, alternative energy sources have been in use in many countries.

The following sections will be dedicated to some types of alternative energy sources.

Hydro power

Hydroelectric power plants absorb the energy produced by water movement, converting it into electricity.

The advantage of this type of energy is that the hydroelectric power plants are durable over time (some plants have been operating for 100 years) and that generate little pollution.

However, it is necessary to build dams for this type of plant, so in addition to the environmental and landscape impact, the emissions caused by the construction of the dam itself must be taken into consideration; in addition to this, water coming from the dams is filtered and flows into the seas without carrying any debris (stones, mud, etc.), leading to erosion of the coasts and beaches.

Geothermal energy

Geothermal plants use the Earth’s natural heat to produce energy, and it is possible to obtain large amounts of energy.

Among the advantages are the low management and maintenance costs and the low use of water (just 20 liters per mega watt of energy produced).

The disadvantages of this energy source are the high construction costs of the plants, the strong smell caused by the emissions; moreover hot water could contain toxic heavy metals (arsenic, mercury, etc.), and in case of leaks it could pollute the soil.

Solar energy

It is the most used form of energy in nature, and is actually used by plants to perform photosynthesis.

This energy source is used for many purposes: from water heating, to fueling cars and aircraft, to energy production, and is also used in agriculture.

The disadvantages are the high costs for the installation, the low energy absorption in the event of cloudy weather (and the fact that solar panels are unusable at night); moreover, solar energy is very powerful but it is not concentrated, which means that in order to collect large amounts of energy it is necessary to build photovoltaic panels in wide areas.

In the last years the efficiency of the photovoltaic panels has increased, and their use is expanding, and more and more often on the roofs it is possible to see solar panels, especially used to heat water.

Wind power

Wind energy has been known since ancient times, and was used by man for navigation or to operate windmills, and we use it today to obtain electricity.

Among the advantages are the relatively low costs for the production and installation of the wind turbines, the little space required for the installation of the single wind turbine and the very low emissions of polluting gas.

However wind turbines are harmful to birds (while there are no negative effects on other animals), and have a negative impact on the landscape.

Moreover, in case of fire, the fire-extinguishing operations would be difficult, due to the height of the wind turbines.

Energy from biomass

Biomasses are organic materials (i.e. composed of carbon), except for fossil fuels and plastics: those are dung and scraps of farms, unused wood, urban waste, which are burned to obtain electricity.

The advantages of this energy source are the low costs of use, due to the fact that it does not require advanced technologies; the low CO2 emissions and the easy availability of biomass.

However, there are some issues: this energy source is not very efficient; storage of the biomasses requires space, and their transport, besides having a cost, is also polluting, due to the gases emitted by the transport trucks.

Public opinion and environment protection

Over the years public opinion has become increasingly aware of environmental issues, and this is demonstrated by the increase in campaigns and laws on pollution, recycling and environmental protection, in Italy, throughout the European Community and in the world.

Governments have participated and ratified various protocols and conventions on environmental protection, such as the 1997 Kyoto Protocol or the 2015 Paris Agreements, but nations that still use coal and other fossil fuels as energy sources, and are responsible for considerable carbon dioxide emissions, such as the United States and China, have always had doubts about such treaties, since they can damage their economy.

Associations like Greenpeace and the WWF have been fighting for decades to protect the environment, by the means of awareness and information campaigns aimed at the general public, and more and more people are worried about climate change and environmental preservation.

In recent years public opinion has been in favor of renewable energies and recycling, and thanks to technology we are changing our habits, making progress towards environmental protection: we buy low-consumption LED lamps, we drive more efficient, less polluting, hybrid (or even electric) cars; appliances are increasingly efficient and use less electricity; we do separate waste collection and recycle.

We are increasingly aware that we must act as soon as possible and prevent global warming from increasing, otherwise the consequences for mankind will be devastating.

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