**4. CO2 emissions**

Atmospheric CO2, which stands at ~400 ppm, is both harmful and vital. Without the significant greenhouse gas CO2 and other natural greenhouse gases, the Earth's average surface temperature would be sub-zero, and life would not be possible. This natural balance is disturbed by excessive and increasing anthropogenic CO2 emissions. These disturbances lead to global warming, which has developed since the Industrial Revolution (~1750) and increased significantly in recent years [3, 22].

The steadily growing globalization is making a significant contribution to the greenhouse gas effect. Carbon dioxide is also produced in combustion processes of engines and other equipment, with most of the artificial and harmful CO2 emissions caused by the industrialized countries. In addition to carbon dioxide, e.g., methane (CH4) and nitrous oxide (N2O) contribute to the environmental impact. These gases have a higher global warming potential (GWP) than CO2 [23]. All greenhouse gases can be converted into CO2eq (CO2 equivalents) [3].

#### **4.1 Natural and anthropogenic greenhouse effect**

Natural greenhouse gases act as a kind of filter that lets the (short wavelength) sun's rays through and captures the heat radiation (long wavelength) from the Earth's surface, thereby enabling regulated global warming. The functioning of a greenhouse is also used, for example, in plant breeding. Colloquially, the term greenhouse

gas effect is used for global warming [22]. The presence of gases with GWP results in an increase in temperature and thus the greenhouse gas effect. Many scientific predictions suggest that the Earth will continue to warm without a reduction in CO2 emissions [23], e.g., by 2°C when the atmospheric CO2 concentration can be kept at or below 650 ppm, and significantly higher if it cannot [10]. In August 2018, the IPCC has released a special report, pledging to limit global warming to 1.5°C [24]. "Limiting global warming to 1.5°C compared with 2°C would reduce challenging impacts on ecosystems, human health, and well-being," said Priyadarshi Shukla, Chair of the Global Centre for Environment and Energy, Ahmedabad University, India, and the co-author of the report.

Under the 2015 Paris Agreement [25], countries have agreed to keep global temperatures increase below 2°C, which might not be enough to avoid exceeding dangerous tipping points.

#### **4.2 The Kyoto Protocol**

The Kyoto Protocol [26] is an agreement made in 1997. It regulates the United Nations Framework Convention on Climate Change (UNFCCC) and focuses on climate protection. In doing so, an international and joint agreement was achieved, which should gradually reduce CO2 emissions worldwide. The Kyoto Protocol is designed to slow down the progressive effects of greenhouse gases and, if possible, to halt artificial global warming [23].

The statistics in **Figure 4** shows the 10 largest CO2-producing countries by share of global CO2 emissions in 2016. With a very high proportion of over 28% of global carbon dioxide emissions, China was the world's largest CO2 emitter in 2016. Second only in the list of climate sinners come the USA with almost 16%. In addition to carbon dioxide, the Kyoto Protocol includes another five greenhouse gases: methane (CH4), nitrous oxide (N2O), "F-gases" hydrofluorocarbons (HFCs), perfluorocarbons (PFC), and sulfur hexafluoride (SF6). Nitrogen trifluoride (NF3) must be additionally included since 2015. In 2015, Germany was able to reduce almost all greenhouse gases compared to the year 2000 (with the exception of hydrofluorocarbons) and thus already meets the requirements of the Kyoto Protocol [27].

**119**

possible [28].

**Figure 5.**

**5. Rail freight**

chain [4] (compare **Figure 5**).

*Energy Efficiency Management: State of the Art and Improvement Potential Analysis…*

Nearly two-thirds of global carbon dioxide emissions are caused by 10 countries, around a quarter or one-sixth by China and the USA alone, respectively. Germany ranks sixth in that list. For the total emissions of a country, both the number of inhabitants and the per capita emissions are relevant. In short, an American causes almost twice as much carbon dioxide as a German and about 10 times as much as an Indian citizen. Worldwide, the carbon dioxide emissions and the carbon dioxide concentration in the atmosphere are steadily increasing. Energy-related carbon dioxide emissions have more than doubled worldwide since 1970 and increased more than 15 times since the beginning of the last century. Since 2013, however, emissions have grown significantly more slowly. This gives a little hope that a stabilization and then a trend reversal can be made

*Carbon dioxide emissions of transport (in kt) in Germany in 1960–2014 and in the trend scenario until 2035 [30].*

The Transport Emission Model (TREMOD) [29] is a commonly used method of determining CO2 emissions. The TREMOD takes into account direct emissions from vehicles, evaporative emissions, and total emissions with the energetic upstream

In the transport sector, not only the specific energy consumption but also the development of CO2 emissions is an important indicator of energy efficiency. Concerning CO2 emissions, very different information is given in the transport sector, mainly because of the increased use of specific energy sources and significant differences in the CO2 balance among the individual modes of transport [4].

According to a study by SCI traffic "Rail Transport Markets-Global Market Trends 2016–2025," global rail freight traffic fell by 4.4% in 2015 [31]. Thus, the rail freight traffic has recorded negative growth for the first time since many years. The reason for this is the slowdown in the transport of coal and steel due to weaker production activity and also the decline in international trade growth. In the face

*DOI: http://dx.doi.org/10.5772/intechopen.86552*

**Figure 4.** *The 10 countries with the largest share of CO2 emissions worldwide in 2016. Modified from [27].*

*Energy Efficiency Management: State of the Art and Improvement Potential Analysis… DOI: http://dx.doi.org/10.5772/intechopen.86552*

**Figure 5.** *Carbon dioxide emissions of transport (in kt) in Germany in 1960–2014 and in the trend scenario until 2035 [30].*

Nearly two-thirds of global carbon dioxide emissions are caused by 10 countries, around a quarter or one-sixth by China and the USA alone, respectively. Germany ranks sixth in that list. For the total emissions of a country, both the number of inhabitants and the per capita emissions are relevant. In short, an American causes almost twice as much carbon dioxide as a German and about 10 times as much as an Indian citizen. Worldwide, the carbon dioxide emissions and the carbon dioxide concentration in the atmosphere are steadily increasing. Energy-related carbon dioxide emissions have more than doubled worldwide since 1970 and increased more than 15 times since the beginning of the last century. Since 2013, however, emissions have grown significantly more slowly. This gives a little hope that a stabilization and then a trend reversal can be made possible [28].

The Transport Emission Model (TREMOD) [29] is a commonly used method of determining CO2 emissions. The TREMOD takes into account direct emissions from vehicles, evaporative emissions, and total emissions with the energetic upstream chain [4] (compare **Figure 5**).

In the transport sector, not only the specific energy consumption but also the development of CO2 emissions is an important indicator of energy efficiency. Concerning CO2 emissions, very different information is given in the transport sector, mainly because of the increased use of specific energy sources and significant differences in the CO2 balance among the individual modes of transport [4].
