Many discover now the problem not having read the Pope's encyclical on its fifth anniversary, or having followed any free course offered on the internet for the last 10 years or having heard neither of the Rome club nor the studies on climate change, on the history of the ice ages, the Holocene and the Anthropocene.

The movement’s credit is to have attracted the attention of young people. No one wants to steal youth’s future, but it is certainly up to them to grow up with a conscience at least partly lacking in the past and assume the responsibilities that the political and business world is perhaps not willing to take. However, the manifestations and emotions aside what certainties remain? There are

few, and of those they already debated at the UN by heads of States and turning around the costs and implications of an answer to the phenomenon. Massimo Famularo summarizes them in the article, Tre cose non trascurabili di cui Greta Thunberg non parla (Three important things that Greta Thunberg does not talk about). Every strategy against global warming is a problem of coordination; the majority of CO2-producing activities cannot be changed in the short term without high costs; the allocation of immediate costs must be part of any cooperation agreement.

It starts from an image: we are all on the same train and everyone has the remote control in his or her hands and can increase or decrease the train’s speed. Travelers of the past have accelerated, or allowed the speed of the train to accelerate, at the point where it became dangerous. Were things to continue like this, eventually the train would derail, even though we do not know exactly when and at what speed.

What do we have to do?

No one did want or wants such a disaster: we are all on the same train and we are all responsible for its speed, some in a marginal way, others in a much more consistent way, a few in a conscious way and many unconsciously because they only search their own results not keeping in account the train’s speed. There is not, in any case, a group of adults, were they ordinary people or people in power, who "can sit at a table to decide and halve greenhouse gas emissions under the youth’s watchful eyes".

Not even a world dictator, says Famularo, could "force billions of individuals" to change their behavior all at once and all together. The necessary changes require "reconciling different and often conflicting needs". In fact, "they put actual individual survival at risk in a change of a future collective benefit". Rich countries could reduce pollution with "a responsible choice, requiring costs and sacrifices" but not "questioning their basic needs". Meanwhile developing countries, with high fertility rates and a high negative environmental impact, "need to pollute" to survive, or to improve the quality of their lives and reach the level of developed countries.

Young people ask for an immediate response because the problem is urgent. Unfortunately, immediate-effect actions, such as using public transport instead of cars, are individual and marginal. The flight Greta did not board, took off even without her, and vegetarians did not prevent the meat market from flourishing. Strategies capable of consistently reducing emissions need time and high social and economic costs, as in the case of heating and cooling systems.

If fast and inexpensive solutions are marginal, what to do in the medium term? Greta's gestures have helped to give visibility to the problem and the movement has moved the consciences of young people and adults: who has to act now? The slogan, "we will keep an eye on" seems to say that it is up to someone who has all the controls in their hands and who is not on the train. "The only effective road - Famularo suggests instead - consists in the promotion of a sustainability culture, which induces people to change their individual behavior and to put pressure on their governments so as to obtain environmental regulations driving to the reduction of greenhouse gases". Young people have a call to assume global commitments that must be immediate, if they see an urgency, and visible if they want to change the system: giving up scooters for bikes, using a mobile phone only when necessary, going on foot and in parks instead of in nightclubs, reducing the consumption of fashionable products, just to give some examples. "To obtain effects it is necessary that the demand for consumption with its negative environmental impact is reduced to such an extent as to induce also the producers to modify the offer," recalls Famularo.

This is certainly true for adults too, but - and in this the movement in progress is right - the most at risk are young people because it is up to them to live in the future and to face the consequences of the present.

Would limiting population growth be an effective strategy to reduce environmental impact? In mathematical terms, it seems obvious: less people, less consumption, less pollution. However, in the developed countries the demographic winter has already been underway for some time with no impact on climate change, and in poor countries, where social services - education, health, social assistance - are poor or absent, is the number of children supplying for them. Famularo suggests that the only way is the intervention programs funded by developed countries helping developing countries to reduce greenhouse gases without compromising people's well-being.

Climate change is not a phenomenon in its own but a consequence of pollution that, in turn, is caused by the excessive and disorderly exploitation of resources. For this reason, Pope Francis recalls that the climatic and ecological emergency cannot be resolved if the social emergence of inequality is not. Actually, everything is interconnected: the tree of climate change should not hide the forest. The future well-being of young people like Greta will never be protected if the future well-being of the poor countries’ children is not assured. Securely, the road to hell is paved with good intentions; however, paraphrasing Vincent de Paoli, a saint who knew how to perform miracles, we can say: emotions are essential to shake consciences, but to solve problems we ought to use intelligence.