What are global warming and climate change and what are they caused by? Let's look at it in a nutshell. Since the first Industrial Revolution, developments in human activity has led to an increase in the emissions of certain gases (known as ‘greenhouse gases’). The greenhouse gases emitted, in turn, remain in the atmosphere in the long-term, so their concentration in the atmosphere increases every year. Finally, the increase in the concentration of greenhouse gases means that the Earth's atmosphere traps more of the energy received from the Sun, thus resulting in rising temperatures and climate change. If the increase in greenhouse gas emissions caused by human activity (known technically as ‘anthropogenic’ greenhouse gases) continues in the future at the same pace as in recent decades, the largest scientific community – which has been studying this topic for decades – (the IPCC, the UN Intergovernmental Panel on Climate Change), estimates that it could trigger a major rise in temperature and the climate. This would potentially be harmful to humans and the environment. As a great deal of the increase in anthropogenic greenhouse gases in the atmosphere is due to increased carbon dioxide emissions from the burning of increasing amounts of fossil fuels (coal, oil and natural gas), the issue of combating climate change is closely linked to that of the transition to a new system capable of ensuring economic development and universal access to energy and thus gradually reducing greenhouse gas emissions to zero. 

Is there anything we can do to reduce greenhouse gas emissions and change the coming scenario of inertia, to reduce and limit the associated risk of harm to humans and the environment? The answer is yes, although finding a solution to this problem is a complex, not simple exercise, precisely because management of the energy transition is complex. What options are available to achieve this? Let's start by looking at the variables that determine the level of greenhouse gas emissions generated by energy consumption. We will do this using Kaya's equation (named after its inventor), a synthetic but clear and effective mathematical representation.

To the left of the equals sign is the level of greenhouse gas emissions generated in a year by production and use (mainly combustion) of fossil fuels. The name of the variable representing these is Tot GHG (GreenHouse Gases). The first factor to the right of the equals sign is greenhouse gas emissions per unit of energy consumed, i.e. the emissive intensity of energy. This variable is the ratio of total greenhouse gas emissions (Tot GHG) to total primary energy consumption, identified by the Tot Ene variable. 

This is followed by multiplication by a second factor, the ratio of total energy consumption (Tot Ene) to Gross Domestic Product (GDP). Gross Domestic Product is the technical term used by economists to indicate the total value of goods and services produced by a country in one year. Therefore, this ratio measures energy intensity, i.e. the amount of energy consumed on average to produce one unit of value of goods and services. 

This is followed by multiplication by a third factor, output per capita, which is the ratio of a nation's GDP to its population. This measurement indicates the average level of economic well-being per inhabitant, given that a country's GDP, as the value of the sale of production of all goods and services, also accounts for the majority of the annual income received by the population as remuneration for work or capital assets. 

The final multiplication factor in the identity is population. If we multiply the greenhouse gas emissions associated with the consumption of one unit of energy by the amount of energy required to obtain one unit of production, we obtain the greenhouse gas emissions associated with one unit of production. If we then multiply this result by average production per individual inhabitant, we get average greenhouse gas emissions per head of population. Finally, if we multiply this value by the number of inhabitants, we get the total greenhouse gas emissions emitted by that country. 

In short, this equations tells us that the level of greenhouse gas emissions produced by a country's energy system depends on the emissive intensity of greenhouse gases in the energy mix used by that country, the energy intensity of production, the level of production (or income) per capita and the population. If we want to cut emissions, one or more of these variables must be reduced. If any of these variables then increases, its impact must be more than compensated for by reducing the others. The final two variables – per capita production and population – are particularly critical, as their future growth is almost inevitable. In many countries, poverty is still widespread and there is a need for greater production to raise the average level of income (and, consequently, the average world output per person). Equally, controlling the growing population of the Earth is practically impossible. As we saw in the energy transition course, the United Nations expects that by 2050, the world population will reach around 10 billion, compared to the current 7 billion.

Energy Sector Integrated Technical Studies Eni, Development, Operations & Technology.