According to the definition given by the United Nations, the expression climate change refers to long-term shifts — we are talking about at least 30 years — in temperatures and weather patterns (that is, forecasts drawn up on the basis of a series of variables such as temperature itself, humidity, atmospheric pressure, and so on).

These shifts can occur naturally. However, it is scientifically proven that, since the nineteenth century, human activities have been the main cause of global warming, primarily through the use of fossil fuels such as coal, oil and natural gas, which release greenhouse gases into the atmosphere.

The ongoing environmental crisis, in several respects, makes it more urgent to adopt tools and actions to reduce emissions of these gases into the atmosphere. Once the causes of emissions have been identified, depending on their nature, there are various technologies that can be applied to mitigate the rise in temperatures and, consequently, the effects of climate change. Let us look at which ones.

• Causes and consequences of climate change
• Which sectors are most responsible for climate change
• The energy sector: technologies for decarbonisation
• Transport, construction and industry: solutions for reducing emissions
• Climate change and agriculture: a look towards the future
• Circular economy: mitigating the impact of waste
• We have until 2025

Causes and consequences of climate change

First of all, let us try to understand what climate change is. The problem of global warming concerns a rise in the average temperature on Earth caused by an excessive concentration of various gases present in the atmosphere.

These are principally four types of gas: carbon dioxide (CO2), methane (CH4), nitrous oxide (N2O) and hydrofluorocarbons. The main driver of rising temperatures in the atmosphere is undoubtedly CO2. It can remain in the atmosphere for very long periods — even hundreds of thousands of years (which is why the effects of mitigation techniques cannot be immediate) — while methane has a shorter atmospheric lifetime but traps far more heat than CO2 (25 times more), and for this reason plays an important role in intensifying the effects of the climate crisis in the short term.

According to the sixth assessment report of the Intergovernmental Panel on Climate Change (Ipcc), greenhouse gas emissions resulting from human activities are responsible to date for warming of approximately 1.1 degrees Celsius since the beginning of the twentieth century. The trend observed from 2000 to the present suggests that, in the absence of intervention, it could reach more than 1.5 degrees between 2030 and 2050.

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The consequences of climate change for ecosystems and populations have been tangible for some time now. These include the melting of glaciers, rising sea levels, ocean acidification, desertification and the loss of biodiversity.

Which sectors are most responsible for climate change

In 2019, again according to the Ipcc, 34 per cent of emissions produced by human activity came from the energy sector, 24 per cent from industry, 22 per cent from agriculture, deforestation and land use, 15 per cent from the transport sector and 6 per cent from the construction sector. For each of these sectors there are various technologies capable of reducing emissions and, consequently, mitigating the effects of global warming.

The energy sector: technologies for decarbonisation

The energy sector is undoubtedly the largest contributor in terms of emissions, since the extraction and combustion of fossil fuels has generated, from the advent of the Industrial Revolution to the present day, the majority of emissions in the atmosphere. For this reason, the main efforts are focused on the energy transition, through the replacement of fossil and non-renewable sources with renewable energy sources that produce far lower emissions. We are talking in primis about technologies that harness various forms of energy: solar, wind, geothermal, hydroelectric, biomass and marine. As of 2022, solar and wind account for 10 per cent of global energy production, and all renewables combined reach 38 per cent.

The new clean sources — sun, wind, waves, tides — are characterised by being more intermittent than fossil fuels, which is why new technologies are needed, such as energy storage batteries for the energy produced. Among the innovations worth mentioning are smart grids, intelligent electricity networks. These are grids equipped with new communication systems capable of enabling users to interact effectively with the network operator: this means they monitor branches in real time, communicate with users and meters, connect electricity producers with users, and analyse and regulate energy flows.

A possible alternative to natural gas, with a lower carbon footprint, is the so-called circular gas, derived from the recovery of waste that cannot be mechanically recycled. If 16 million tonnes of municipal and special waste were used to produce circular gas instead of ending up in landfill, enough would be obtained to replace 8 billion cubic metres of natural gas — that is, 57 per cent of the natural gas consumed every year in Italy by industry.

A trend also supported by the European Union sees the use of low-emission or green hydrogen as a replacement for gas. Unlike grey hydrogen produced through fossil fuels, green hydrogen is obtained from water and renewable energy through electrolysis. There is also another type of low-emission hydrogen — circular hydrogen — generated through the chemical conversion of waste. One example is the waste-to-hydrogen project that forms the Hydrogen valley of Rome. It was developed by NextChem (a company belonging to the Maire Tecnimont group) and received a grant of almost 200 million euros from the European Commission under the Ipcei (Important Projects of Common European Interest) programme.

Transport, construction and industry: solutions to reduce emissions

Further mitigation measures can then be applied to all those sectors that use energy. Energy is, in fact, a vector used to drive various branches and sectors of the economy, which in turn generate emissions. Think of the field of transport (road, air, rail, maritime), of construction, of industrial production (steel, iron and so on); think of the energy used in agricultural production activities and in fishing. Each of these sectors can put in place actions to reduce the use of fossil energy, replacing it with low- or zero-emission energy.

In the case of transport, for example, this transition is proceeding through the electrification of vehicles and infrastructure, the use of biofuels and recycled-carbon fuels, or indeed through hydrogen; in the case of construction, on the other hand, through the energy efficiency retrofitting of buildings, with the replacement of gas boilers with electric heat pumps powered by photovoltaic panels, making extensive use of digitalisation and artificial intelligence.

In the production of steel and iron, for example, various techniques are being tested, including the use of hydrogen in steelworks. Steel, in order to be produced, requires the reduction of iron oxides. One of the low-carbon processes for obtaining steel is "direct reduction", which involves using low-emission hydrogen in place of coal, the latter generating far greater atmospheric emissions. In this sense, low-emission hydrogen could "clean up" heavy industry: think of an application of this kind at the former Ilva steelworks in Taranto.

The possibility of capturing the CO2 emitted must also be considered, with a view to reusing it in industrial processes (such as the production of green fertilisers) or storing it in geological formations, either temporarily or permanently.

Climate change and agriculture: a look towards the future

Now, beyond the type of energy used, the other sectors that contribute most in terms of emissions are, as we said, agriculture, industry and waste disposal, considered here net of the type of energy used.

Take agriculture: livestock farming, fertilisers and deforestation are aspects on which it is necessary to act with a change of paradigm, as well as with the appropriate technologies. A study published in the scientific journal Plos climate goes as far as saying that without intensive livestock farming, emissions would be reduced by as much as 68 per cent, with the areas currently dedicated to animal grazing and feed cultivation being recovered. A crop such as soya, widely used in the meat and meat-products industry, contributes to the destruction of entire ecosystems.

Given that by 2050 the world will need 60 per cent more food to feed its inhabitants (UN data), "green" fertilisers obtained through the use of hydrogen from renewables and recovered CO2 are being developed. Another possible solution is vertical farming. Also known as vertical farming, it is the indoor cultivation of plants and vegetables in a greenhouse, one above the other, using special structures similar to stacks. It consumes less land but also less water, because it is able to reuse all the water not absorbed by the plants, in a continuous cycle.

Circular economy: mitigating the impact of waste

Waste is a chapter of its own, and one on which it is certainly easier to focus in the short term. The theme of the circular economy is undoubtedly one of the cornerstones in the sustainable development of societies. It represents a change of approach that involves, first and foremost, reducing the quantity of raw materials fed into the system, redesigning goods and manufacturing cycles, extending the lifespan of goods and ensuring that they can be repaired and reintroduced into the economic system. In this way, the circular economy preserves the planet's resources and avoids generating waste (which in turn produces emissions).

Within this broad topic, ecodesign plays an extremely important role: the entire process of conceiving and designing everyday objects must pursue the minimisation of environmental impact. The use of raw materials and the quantity of waste generated when a product or packaging becomes refuse depend, in fact, on the design of that product. To be sustainable, therefore, a product must place the criteria of durability, repairability, upgradeability and recyclability of the materials used at its centre. In short, its lifecycle must be extended as far as possible.

Secondly, it is essential to increase recycling activities (both mechanical and chemical) for waste that cannot be recycled using traditional methods, generating new, recycled, high-quality materials that can be regarded as secondary raw materials, thereby avoiding disposal in landfill or via incineration.

We have until 2025

The Ipcc has set 2025 as the moment by which emissions must peak, before being reduced by at least 43 per cent by 2030 compared to 2019. This is the necessary condition for keeping the increase in average global temperature within 1.5 degrees relative to the pre-industrial era.

From the moment we publish this article, therefore, we have three years to develop all the solutions described here. Or at least the majority of them. A challenge that we must keep clearly in mind not only at a personal level but above all collectively. Because while it is true that each of us can play our part, it is certainly necessary for the centres of power (governments, institutions, businesses and multinationals) to undertake the requisite political and social actions as soon as possible.