Different causes of climate change
The Earth’s climate has been constantly evolving at varying rates since the very beginning, yet these fluctuations have been slow in comparison to the current one. It is important to consider the speed of this variation, the so-called “timescale” of the changes, in order to understand the different contributions of natural and anthropogenic activities to current climatic changes.
The average temperature is regulated by the balance between incoming and outgoing energy, which determines the Earth’s energy balance. As such, any factor that causes a change to the amount of incoming or outgoing energy, which is sustained over a long period (decades or more) can lead to climate change. Some of these factors could be natural or “internal” to the climate system, such as changes in volcanic activity, solar output or the Earth’s orbit around the Sun.
Other causes are “external” to the climate system and are referred to as ‘climate forcers’, evoking the idea that they force or push the climate towards a new long-term state. This may be warmer or cooler depending on the cause of the change.Different factors operate on different time scales, and not all of the factors that have been responsible for changes to the Earth’s climate in the distant past are relevant to contemporary climate change.The two natural factors relevant to the timescales of contemporary climate change are changes in volcanic activity and solar radiation.
These factors primarily influence the amount of incoming energy. Large volcanic eruptions that emit enormous quantities of dust and sulphates cool the atmosphere, but this contribution is episodic and has relatively short-term effects on the climate (lasting from a few months to a few years). Changes in solar irradiance have contributed to climate trends over the past centuries, but since the industrial revolution the effect of increased greenhouse gas levels in the atmosphere has made approximately 10 times the contribution to “climate forcing” than the effect of variations in the Sun’s output.
Variations in ocean currents or atmospheric circulation (e.g. the El Niño phenomenon), can also influence the climate for short periods of time. Although this is important due to its effect on human activities as it determines hotter years, harsher droughts or heavier precipitations, this natural internal climate variability doesn’t contribute to the long-term trend which is instead regulated by the amount of anthropogenic climate forcers, mainly the greenhouse gases added to the atmosphere Scientists believe that natural changes alone cannot explain the temperature changes of the last 50 years. Using computer models they reproduce the different climate forcers (both natural and anthropogenic), first ensuring that these models are able to reproduce the temperature changes observed in the recent past.
When the models only include natural climate drivers (such as sun intensity variation and volcanic eruptions), they cannot accurately reproduce the warming that has been observed over the past half century. When human-induced climate drivers (greenhouse gases) are also included in the models, they are then able to replicate the recent temperature increases in the atmosphere and in the oceans.
When natural and human-induced climate drivers are compared to one another, the dramatic accumulation of carbon from human sources is by far the largest climate change driver in the past half century.
Stefano Caserini – Istituto Oikos
Are we equally responsible for the increase of CO2?
We all live on the same planet and one of the aspects that we share with the other inhabitants of the Earth is the impact of emissions altering the planet’s climate, which are leading us rapidly towards disaster.
Greenhouse gases affecting climate change spread very rapidly through the Earth’s atmosphere.
Therefore, climate change will have severe consequences upon certain regions of the Earth, without any direct relation to the areas from which the emissions have been produced over time and space. How can we measure each country’s responsibility for greenhouse gas emissions and consequent climate changes?
The point is not to blame anyone (since, until 50 years ago, few people knew or imagined that climate change would become one of the main threats to human life on Earth).
Nevertheless, in the international negotiations on climate the responsibility of each country should be taken into account. But the real goal is to identify, in the fairest possible way, the measures that each inhabitant of the planet, each area, and each single government could adopt to mitigate and reverse the emission trends.
There are three main criteria for this.
The first is based on measuring each country’s per capita greenhouse gases emissions
Over time, these numbers must become progressively more uniform and lower in order to stop the emissions (before the irreversibility threshold is reached. But how can we measure each country’s emissions against the lifecycle of products? Some emissions are due to the production of goods, which are then consumed in other parts of the world. Should those emissions be attributed to the producing country or to the consuming country.
The second criterion is of a historical nature; industrialisation, the source of most emissions contributing to climate change, started in different periods in different countries (in many countries, it has not started yet). This is why, in order to achieve convergence, the calculation of each country’s share of CO2 emissions having accumulated in the atmosphere over two centuries (estimates are, of course, quite general) should take into consideration this element — called historical responsibility.
Lastly, some countries are now beyond the most intense phase of industrial development offshoring of several polluting manufacturing activities is evidence of this); of several polluting manufacturing activities is evidence of this); on the contrary, several economies still count on manufacturing for development and this generates a high amount of emissions causing climate change, especially when they cannot rely on the environment-friendly technologies and know-how which are the monopoly of more industrially advanced countries.
Therefore, when calculating each country’s share of emissions contributing to climate change and how much each country should be allowed to produce before the irreversibility threshold is reached, we must take into account the economies still undergoing the industrialization process or lagging behind in development. The convergence underpinning the creation of a shared road map of measures to counter climate change should be based on these three factors.
Guido Viale – Cies Onlus
Short, medium and long term effects of CC
Over the past decades, climate change has caused a variety of effects on human and natural systems on all continents; as global warming increases, over the next few years other impacts are expected in the short term. Many terrestrial, freshwater and marine species have shifted their geographic ranges and migratory habits in response to climate change.
The speed of current climate change is higher than in the past, making it more difficult for species to adapt; for this reason it is expected that global warming will be a very important element in the increasing extinction rate of living species.
In many regions of the planet, changes in rainfall, snowfall or the consistency of alpine glaciers are causing changes to the hydrological systems, impacting on the quality and quantity of water resources. Glaciers have shrunk across almost the entire planet while the seasonal summer decline of Arctic sea ice is increasing.
For human societies, the impact of climate change generally worsens existing critical situations (poverty, lack of food, poor land management, migration due to wars, etc.), affecting the poorest and most vulnerable people in particular.
Specifically, extreme events such as heat waves, droughts and storms have already shown a direct impact on living conditions, through floods, forest fires, the decrease in agricultural yields and the destruction of housing and infrastructure.
However, other more indirect consequences include rising food prices and migration. Further global warming increases the likelihood of severe, widespread and irreversible effects. Given the officially acknowledged increase in global temperature (on average approximately 1°C higher than pre-industrial levels) other consequences are inevitable, with the temperature predicted to rise by an additional degree in the medium term, i.e. over the next few decades.
Without serious action to reduce greenhouse gas emissions, the global average temperature may rise by 4°C or more, resulting in severe and widespread impacts on the most fragile ecosystems, a substantial reduction of biodiversity, and significant threats to global food security in many densely populated regions. The combined effect of high temperatures and humidity can make it difficult to carry out many normal human activities, such as working outdoors, in some areas and seasons.
The future impact of climate change will vary greatly depending on the region; effects will not be distributed equally or uniformly due to a number of different factors, one example being that some low coastal areas and small islands in the Pacific will suffer greater effects from rising sea levels. However, it isn’t just a question of geography; richer countries will be less vulnerable to damage and better able to take advantage of any potential benefits, because these areas are typically less densely populated and have more resources to invest in prevention and adaptation. In contrast, the poorest countries will be hit harder, since they rely more directly on local agricultural production and are therefore more vulnerable to the effects of changing temperatures and hydrological cycles.
Stefano Caserini – Istituto Oikos
Individual daily choices for mitigation
The term “climate change mitigation” refers to measures aimed at reducing emissions of CO2 and other greenhouse gases and at increasing the absorption of CO2 by forests (read more… (link to unit 8.1 Edukit)) Acting to improve the conditions of our planet and help the affected communities is not only the responsibility of those at political, economic and administrative levels; our daily lifestyles are also important.
Anna Brusarosco – CeVi
A useful tool to understand the impacts of our habits on environment is the Ecological Footprint, an index used to assess the human consumption of natural resources compared to the planet’s capacity to restore them. It represents the productive area required to provide the renewable resources humanity is using and to absorb its waste.
Two other similar indexes have been developed: the Water Footprint , a measure of humanity’s appropriation of fresh water in volumes of water consumed and/or polluted, and the Carbon Footprint, the total amount of greenhouse gases produced to directly and indirectly support human activities.
By measuring these indexes for a population — an individual, city, business, nation, or all of humanity — we can assess our pressure on the planet, which helps us manage our ecological assets more wisely and take personal and collective action in support of a world where humanity lives within the Earth’s bounds.
At the same time, comparing “our” values of Ecological, Water and Carbon Footprints with those of the Global South, we can highlight the existing disparities and our responsibility, as citizens of the Global North, towards the other communities suffering the consequences of our development model, while having a lower impact on ecosystems. We must launch the message that change is possible, and we all need to act locally, starting from our daily choices, to mitigate climate change.