23.
The climate is a common good, belonging to all and meant for all. At the global level, it is a
complex system linked to many of the essential conditions for human life. A very solid scientific
consensus indicates that we are presentlywitnessing a disturbing warming of the climatic system. In
recent decades this warming has been accompanied by a constant rise in the sea level and, it would
appear, by an increase of extreme weather events, even if a scientifically determinable cause cannot be
assigned to each particular phenomenon. Humanity is called to recognize the need for changes of
lifestyle, production and consumption, in order to combat this warming or at least the human causes
which produce or aggravate it. It is true that there are other factors (such as volcanic activity,
variations in the earth’s orbit and axis, the solar cycle), yet a number of scientific studies indicate that
most global warming in recent decades is due to the great concentration of greenhouse gases (carbon
dioxide, methane, nitrogen oxides and others) released mainly as a result of human activity.
Concentrated in the atmosphere, these gases do not allow the warmth of the sun’s rays reflected by the
earth to be dispersed in space. The problem is aggravated by a model of development based on the
intensive use of fossil fuels, which is at the heart of the worldwide energy system. Another
determining factor has been an increase in changed uses of the soil, principally deforestation for
agricultural purposes.
24.
Warming has effects on the carbon cycle. It creates a vicious circle which aggravates the
situation even more, affecting the availability of essential resources like drinking water, energy and
agricultural production in warmer regions, and leading to the extinction of part of the planet’s
biodiversity. The melting in the polar ice caps and in high altitude plains can lead to the dangerous
release of methane gas, while the decomposition of frozen organic material can further increase the
emission of carbon dioxide. Things are made worse by the loss of tropical forests which would
otherwise help to mitigate climate change. Carbon dioxide pollution increases the acidification of the
oceans and compromises the marine food chain. If present trends continue, this century may well
witness extraordinary climate change and an unprecedented destruction of ecosystems, with serious
consequences for all of us. A rise in the sea level, for example, can create extremely serious situations,
if we consider that a quarter of the world’s population lives on the coast or nearby, and that the
majorityofourmegacities are situated in coastal areas.
25.
Climate change is a global problemwith grave implications: environmental, social, economic,
political and for the distribution of goods. It represents one of the principal challenges facinghumanity
