Barcelona for Climate

The answer to this question is made up of various arguments that complement one another:

• Because this is the first climate change caused by human activity, while the previous episodes were the result of natural causes.
• Because this is the fastest climate change ever experienced on Earth.
• Because it is causing an increase in average temperatures which has clear and serious effects on ecosystems and people.
• Because it is unjust and causes inequalities. Not all countries are equally responsible for generating greenhouse gases, and not all countries have the same capacity to adapt. In fact, the countries most affected and with the greatest difficulties adapting to the changes are those that have contributed least to the problem. It is therefore a problem that goes beyond strictly environmental aspects to become a question of ethics and responsibility.

To measure the gases causing the current climate change, we use a standardised measure which is CO2 equivalent. Each of the greenhouse gases has a global warming potential that indicates the capacity it has to contribute to such warming. The values are as follows: 1 CO2, 25 CH4 and 298 N2O. Giving a final formula of: CO2 + 25xCH4 + 298xN2O = CO2 eq. So, while we normally talk about x tonnes of CO2, in reality we are referring to CO2 eq.

Greenhouse gases are found naturally in the atmosphere, although human activity has increased their concentration. They are as follows:

• Carbon dioxide (CO2): produced in large quantities in forest fires and volcanic eruptions. The current excess is due to the use of fossil fuels (oil, coal and natural gas) for energy and their use in vehicles, heating, thermal power stations, industry etc. 
• Methane (CH4): generated as a result of agricultural and livestock activity. Also in landfills, and in wetlands and marshes.Nitrogen oxide: released by crop fertilisers, excrement and livestock.
• Water vapour.
• Gases originating directly from human activity: chlorofluorocarbons (CFCs) from industry, used in air conditioning systems, aerosols, extinguishers etc., and sulphur hexafluoride.

The presence of CO2 and other greenhouse gases in the atmosphere is natural and, in fact, it is one of the things that makes life possible on Earth, as it keeps the planet at the right temperature. The concentration of these gases is the result of a balance between emissions sources and sinks (processes that absorb or fix the gases).

The problem is not whether or not these substances are pollutants, but the fact that we are increasing the concentrations of them and, thus, their capacity to retain the heat reflected by the Earth. Since the industrial revolution, anthropogenic sources have increased significantly, whilst the majority of sinks (oceans, vegetation, rocks, etc.) have much slower cycles. Current emissions may, therefore, take decades or centuries to be absorbed.

The use of fossil fuels has generated both this global warming and the increase in atmospheric pollution and, consequently, worse air quality. Climate change is a global phenomenon, while pollution acts more at a local level when the excessive emission of certain gases causes them to accumulate in concentrations that have a harmful effect on our health. These are nitrogen oxide and suspended particles.

Lastly, when we refer to ozone, we also need to differentiate between:

• the loss of the ozone layer in the stratosphere (considered to be ‘good’ ozone at high altitudes, which makes plant and animal life on Earth possible thanks to the absorption of UV radiation), linked to the use of chlorine compounds such as aerosols, refrigerants and so forth;
• and the presence of tropospheric ozone in the city (considered to be ‘bad’ ozone at low altitudes, which causes irritation and harms plants and animals due to its oxidising power, and which is also a greenhouse gas). This ozone forms when the nitrogen oxide gases from industrial and vehicle emissions react with volatile organic compounds (carbon found in chemical products that evaporate easily into the air, such as solvents in paint). 

The greenhouse effect is a natural phenomenon that supports life on Earth. It is related to the absorption capacity, the percentage of solar radiation reflected in the form of heat and its retention in the atmosphere by greenhouse gases (CO2, N2O, CH4), which represent 1% of the atmosphere’s composition. Increased emissions of these gases due to human activity produces global warming, increasing the average temperature of the planet (currently 15°C) and, as a consequence, causes changes in the climate and other effects:

• Reduced snow and ice (increasing albedo).
• Increased ocean temperatures (reduced sink capacity).
• Ocean acidification.
• Rising sea level.
• Increases in extreme weather events.
   

To clarify the relationship between these concepts, it can be said then that the imbalance generated in the composition of the atmosphere is what causes the warming, and this aspect is resulting in climate change all over the planet.

Any activity that uses energy not produced from renewable sources (solar, wind, etc.) generates CO2 emissions. Some agricultural and livestock activities also generate greenhouse gas emissions. Therefore, it is still extremely difficult to find ‘zero emission’ products or services, unless they require no energy or this energy comes from renewable sources. What we can do, however, is offset these emissions by calculating the amount of greenhouse gases emitted in manufacturing a product or conducting an activity (for example, an aeroplane journey) and invest in a project that enables us to reduce emissions by the same amount.

The carbon footprint of a product is the calculation of the emissions (of carbon) associated with its production from the extraction of the raw materials to the end of its useful life. It is therefore a calculation of the grams of CO_2eq associated with the existence of the product or service in question.

In contrast, when we talk about the ecological footprint, we are referring to the amount of land required to support the needs of a person, community, society and so on. And in the case of ecological rucksack, this also takes into account other elements, such as water consumption, pollutant emissions, land use etc.

The Paris Agreement corresponds to the 21st session of the Conference of the Parties (COP) and the 11th session of the Conference of the Parties Serving as the Meeting of the Parties to the Kyoto Protocol (CMP 11), which was held from 30 November to 12 December 2015 in Paris, France.

The United Nations Climate Change Conference concluded with the adoption of an historic agreement to combat climate change and promote measures and investment for a low-carbon, resilient and sustainable future.

The aim of the Paris Agreement is to keep the increase in global average temperature this century to well below 2ºC and strengthen countries’ ability to deal with the impacts of climate change.

The results of the Conference of the Parties (COP 21) covered crucial areas considered to be essential for climate policy:

• Mitigation: a rapid reduction in emissions to achieve the target temperature.
• A global transparency and accountability system for climate action.
• Adaptation: strengthen countries’ ability to deal with the impacts of climate change. 
• Loss and damage: strengthen their ability to recover from climate impacts. 
• Support: including finance, for nations to build clean, resilient futures.
   

Further information: https://canviclimatic.gencat.cat/ca/oficina/actuacio_internacional/acord_paris/

Renewable energies are a fundamental pillar to reduce the emissions generated by the energy system. However, given the need to rapidly speed up the rate at which emissions are cut, there are other aspects that also need to be addressed, such as:

• The food production system, since agriculture and livestock account for a large part of methane and nitrogen oxide emissions, which are currently increasing much faster than CO2;
• Maintaining and regenerating the world’s forests;
• Transforming the social system on a scale similar to that of technological changes in order to achieve the mitigation levels needed. This includes the way in which we work, how we move around and what we eat, among other aspects.