Increases in natural carbon dioxide concentrations over the past million years during the ice age have periodically increased the Earth's temperature. Warm periods began with a slight increase in sunlight due to a slight shift in the Earth's axis of rotation, or its orbit around the Sun. This extra sunlight caused some warming. As the oceans warmed, they released carbon dioxide. Additional carbon dioxide in the atmosphere amplified the initial warming.

Based on the scientific evidence, it is concluded that during the ice age cycles of the last million years, the level of carbon dioxide never exceeded 300 ppm (parts per million). Before the industrial revolution began in the mid-1700s, the average global carbon dioxide level was about 280 ppm. When continuous CO₂ observations began in 1958 at the Mauna Loa Observatory, the level of carbon dioxide in the atmosphere was already 315 ppm. On 9 May 2013, the average amount of CO₂ measured at this observatory recorded more than 400 ppm for the first time.

It is due to the result of human activity – the extraction and use of various fossil natural resources (such as oil, natural gas, and coal), as the level of CO₂, has increased so significantly since the development of industrialisation.

Also, the cause of climate change is the unsustainable and excessive consumption of goods and services, as well as the increase in transport fuel consumption.

At the moment, it can be seen that global CO₂ emissions continue to increase, because the extraction and use of large amounts of fossil resources continues, resulting in an increase in the concentration of GHGs in the atmosphere, including the level of CO₂.

What are the current signs of global climate change?

The climate of the planet is changing, and the global average air temperature is rising (see Fig. 6). The most significant cause is the emission of greenhouse gases (GHG) as a result of human activity. The associated increase in temperature is causing unprecedented consequences around the world, i.e., glaciers are melting, sea levels are rising, floods and droughts are hitting regions that were previously untouched by such extreme weather, and biodiversity is decreasing, with the disappearance of plant and animal species.

These extreme weather conditions are increasingly affecting the economy, environment, health, and our daily lives, with the following potential consequences:

• extreme weather conditions threaten food production, especially in developing countries;
• water and food shortages can lead to regional conflicts, famine, and refugee flows;
• the risk of extinction of some plant and animal species is increasing;
• sea-level rise threatens coastal populations and low-lying island states.

In the polar regions, the ice is melting twice as fast as just 50 years ago. Glaciers in Europe have lost more than 60% of their mass in the last 150 years, and this process is accelerating.

The planet is not adapted to dealing with human-made pollution and the unimaginable number of resources we use each year. Every year, the day of Earth's resource overspending is ‘marked’. It is the day when we have used up one year's ‘budget’ of nature. This day is calculated by considering the biological capacity of the planet, i.e., the number of resources that the Earth can produce in a given year, and the world's ecological footprint, or the amount of the resources consumed in the given year.

According to the Global Footprint Network, this day was 29 July in 2021. This means that humanity is consuming natural resources 1.7 times faster than the ecosystems can regenerate, and it currently needs 1.7 planet Earths to meet our demand for resources. The last time one Earth was enough for humanity to meet its resource needs was in 1970. In 2020, we managed to postpone the day of overspending a little – until 22 August. This was affected by the pandemic caused by COVID-19, during which the consumption of transport fuel and other energy resources decreased.

These facts are also confirmed by the Annual Report of the World Economic Forum, which identifies the most significant global risks. Such an assessment has been carried out since 2007, in which 500 different risks that could await humanity are analysed annually.

In the last five years, at least one of the most significant global risks is related to the environment and climate change. Moreover, this figure also demonstrates that the water crisis and lack of water is one of the most significant risks directly related to the effects of climate change.

The results obtained by the World Economic Forum are also in line with the announcement made at the end of 2019, where the European Parliament declared a state of emergency in the field of environment and climate both in Europe and in other parts of the world.

Regarding the distribution of GHG emissions by sector, almost ¾ of the world's total GHG emissions are generated by the energy sector– energy consumption in industry, transport, energy consumption in buildings, as well as in agriculture and fisheries. 

Calculations and theoretical conclusions are one aspect that demonstrates that climate change is happening and has a significant impact on our present and future, but the real situations reinforce the calculations and theory. 2019 ended, and 2020 began not only with the spread of the dangerous COVID-19 virus, but also with massive forest fires not only in the Amazon rainforest, but also in Australia, Siberia, and Africa. It was a similar situation in 2021 as well.

Of course, forest fires also occur as a result of natural processes, but they are greatly exacerbated by human activities that want to manage the rainforests for economic gain. Forests are cut down and burnt to make the soil more fertile, and then oil palm plantations are established.

The researchers of the World Resources Institute have concluded that every second of 2019, we lost almost 4,000 m² of tropical rainforest, which is equivalent to the area of six (6) football fields.

Such activities not only lead to the disappearance of the forests but also to soil erosion, loss of biological diversity and lack of drinking water.