Climate change, and in particular global warming caused by the increasing concentrations of greenhouse gasses which lead to an increase of both average and extreme temperatures, together with other natural and-or human-made health stressors, it has proved to have an impact on human health (and disease) in a variegated manners, as numerous studies have shown. Notably heat stress and heat waves can aggravate diseases of the heart, circulatory system and respiratory tract, and can also worsen cerebrovascular disease and diabetes-related conditions, thus leading to increased mortality among elderly people, or the very young, and people with chronic respiratory problems.

Higher temperatures also promote the formation of ozone at low altitude, which can have a negative impact on health by causing a reduction in lung function in these categories of people. Increasingly frequent extreme weather events, such as floods or storms, pose additional risks to human health such as potentially fatal injuries. In addition, heavy rain and flooding, resulting in water pollution, can lead to an increase in infectious diseases including gastrointestinal illness like diarrhea, effects on the body’s nervous and respiratory systems, or liver and kidney damage.

Another aspect of Climate Change is that it affects the air we breathe. Climate Change has modified weather patterns which in turn have influenced the levels of air pollutants such as for example ground-level ozone (O₃) and fine particulate matter especially in determined areas where population and industries are concentrated.

Another important factor is that the increasing levels of carbon dioxide (CO2) in the atmosphere promote the growth of plants that release airborne allergens causing respiratory problems for those people who are particularly sensitive to this factor. Thus ozone and allergens not only influence outdoor air quality but also indoor air quality because these pollutants infiltrate homes, schools and other buildings. Higher pollen concentrations can increase allergic sensitization and asthma and thus impacting on our quality of life.

The consequences of climate change can have a negative impact on mental health also. For instance direct experiences of certain extreme weather events can trigger post-traumatic stress disorders, while concerns or a sense of uncertainty arising generally from ongoing climate change can lead to anxiety and even depression. Naturally actual impact on each individual depends on personal conditions and the capability to deal with stress. However the risk of negative effects on mental health may increase as climate change progresses in intensity.

Further effects of climate change on human health, which can vary according to region and level of development, include the following: rising temperatures causes the blooming of massive amounts of algae and-or cyanobacteria (green-blue algae) capable of producing t toxins that can enter the human body through the food chain or the swallowing of water from lakes or seas causing even fatal diseases.

Then we have to take into consideration the Vectors, is it to say organisms that can transmit pathogens from an infected animal or human being to other animals or humans. Ticks or mosquitoes are a common example of vectors. Climate change is changing the conditions for the spread of pathogens by vectors. In recent decades, for example, due to globalization and favorable climatic conditions, the Asian tiger mosquito has already spread to some parts of Southern Europe. Climate change is also making some northern parts of Europe suitable for mosquito settlement. Tiger mosquitoes can transmit pathogens such as dengue and chikungunya viruses.

Cities, in particular large cities, are major contributors to climate change as urban activities are major sources of greenhouse gas emissions, yet they account for less than 2 percent of the Earth’s surface. It is estimated that cities consume approximately 78 percent of the world’s energy and are responsible for 75 percent of global CO₂ emissions, with transport and building being among the largest contributors.

According to the United Nations the sheer density of people relying on fossil fuels makes urban populations highly vulnerable to the effects of climate change, and in fact the temperatures are usually higher in cities densely populated . Warmer nights can reduce the quality of people’s sleep, compromising their restorative effect. Higher temperatures also lead to higher electricity consumption, for example to power air conditioning systems.

However it seems that cities around the world have already begun to take measures to reduce CO₂ emissions and are putting in place policies to encourage the use of alternative energy sources also in consideration of the high costs of traditional fossil fuels and the transition toward a greener and renewable source of energies which will also lead to a more sustainable economy and contribute in preserving our environment.

Climate change also impacts on agriculture: higher temperatures, higher CO₂ concentration in the air, changes in precipitation patterns and other related meteorological parameters inevitably affect plant growth. When temperature increases to the optimal level then an abundant harvest is obtained, but when this optimal level is exceeded, the yield of the crops will decrease. Even individual days above 30°C can compromise the growth of corn and soybeans. Extreme weather conditions, particularly heat and drought, as well as heavy rainfall, have a negative impact on harvests.

Many plants react to a high concentration of CO₂ in the air by reducing the release of water from the leaves and, at the same time, intensifying photosynthesis. In this way, as long as sufficient water and nutrients are available, it is possible that the growth of the plants increases: the so-called “CO₂ fertilization effect” occurs. To what extent this fertilization effect can compensate for the decrease in yields caused by changes in rainfall and temperature in some areas is still a controversial issue. In any case, however, a higher concentration of CO₂ in the air leads to a lower concentration of nutrients in the plants.

In general, it can be said that, at least up to a global average temperature increase of 1-2 °C (compared to the pre-industrial period), minimal to moderate effects on harvests can be expected, with differences depending on the type of crops and harvest regions. Any further increase in temperature, however, will lead to a sharp reduction in crop yields.

Causes triggering the migration phenomenon are usually multiple: changes to regional weather systems which may reduce access to essential resources such as water, as well as affecting livelihoods, but also differences in income levels may influence migration patterns across the entire world. It is therefore difficult to attribute individual migratory movements exclusively to climate change, just as it is difficult to attribute a single storm or extreme event to global climate change. However it is now widely recognized that climate change is contributing to the movement of a great number of people.

An increase in the frequency and intensity of extreme weather events will lead to an increase in the number of people affected by climate change. If we delay to implement measures to mitigate these changes more and more people living on the coastal areas will be forced to relocate themselves to more secure areas.

Where can people affected by climate change migrate, and whether they can enjoy special protection, are questions which have not yet been answered. In any case the first measures to be taken into consideration are to limit greenhouse emissions and transit toward renewable sources of energy and be more respectful for our Mother Nature acting eco-friendly in our daily lives.

According to the UN Environment Program it is estimated that the global costs to respond to climate change and its impacts is expected to grow to $140-300 billion per year by 2030 and $280-500 billion per year by 2050. What is more, it is expected that rising temperatures are likely to reduce global wealth significantly by 2050. Because of rising temperatures crop yields will fall, disease will spread more easily, and rising seas will consume coastal cities. It is therefore evident the necessity to act fast to limit the negative impacts of climate change which involves three different types of costs: first there are the costs due to damage, for example to buildings and infrastructure (for example: roads, bridges, land, ports), as a result of extreme weather events.

Secondly, there are adaptation costs that result from measures to combat climate change, such as the construction of dams or retention basins for flood protection. Finally, there are the so-called prevention costs, for example the costs of switching from fossil fuels to renewable energies in order to limit future global warming. Global warming in fact as evidenced comes with a big price tag for every country around the world. If we take the US as an example the 80 percent reduction in US emissions that will be needed to lead international action to stop climate change may not come cheaply, the implementation of measures to limit greenhouse gasses and the transition to renewable sources of energy are high but the costs of failing to act promptly will be much greater.

If we want to limit global warming to a maximum of 1.5°C, which is the most desirable solution then high investments are required. On the contrary, limiting warming to a maximum of 3.5°C would lead to significantly lower investment costs, but would increase the costs of damage. Overall, the costs of limiting global warming are probably much lower than the cost of damage caused by uncontrolled warming. It must be stressed that the risk of irreversible damages increases with increasing warming, thus it is better to act now and prevent damages by implementing more environmentally friendly policies to avoid this dramatic scenario.

Through strong national and international action it is possible to reduce greenhouse emissions that cause global warming, but it is necessary to act now to meet the targets contained in the Paris Agreement to limit global warming. The longer we wait and delay the implementation of measures to tackle this issue, the more painful – and expensive – the consequences will be.