On the occasion of the 4th Anniversary of the Laudato Si' Encyclical Letter, Cardinal Peter K. A. Turkson, Prefect of the Dicastery for Promoting Integral Human Development, addressed a Message to the Scientific Community that we publish below:
Distinguished Ladies and Gentlemen of the scientific community,
Some time ago, Pope Francis received some of your colleges, led by the French climatologist Jean Jouzel, a long-serving member of the Intergovernmental Panel on Climate Change (IPCC). They shared the profound concerns of many scientists, experts in the field, regarding the current climate crisis, caused by man’s interference in nature.
In 2015 I published the Encyclical Letter Laudato si’,  moving from concerns about the “cracks in the planet that we inhabit” (LS 163) and hoping to “enter into dialogue with all people about our common home” (LS 3). Its publication was intended to encourage the work of the COP 21 Summit, which led to the historic Paris Agreement on Climate Change, aiming to maintain the average increase in the planet’s surface temperature “well below 2°C” and to “intensify efforts” to limit the increase to 1.5°C. The IPCC Special Report for 2018 on the logic and feasibility of the 1.5°C limit warns us that we have only around a decade to limit this global warming.
The 1.5°C threshold is a critical physical threshold, inasmuch as it would still enable the avoidance of many destructive impacts of climate changes caused by man, such as the regression of the main glaciers and the destruction of the majority of tropical coral reefs. In particular, it would probably safeguard our common home from becoming a “greenhouse”. With global warming of around 1°C confirmed since the Industrial Revolution, we are already witnessing the grave impact of climate changes on people, in terms of extreme meteorological conditions, such as drought, flooding, rising sea level, devastating storms and ferocious fires. The climate crisis is reaching unprecedented proportions. Therefore, the urgency could not be greater.
The 1.5°C threshold is also a moral threshold: it is the last chance to save all those countries and many millions of vulnerable people who live in coastal regions. It is the poor who pay the highest price of climate changes. “Both everyday experience and scientific research show that the gravest effects of all attacks on the environment are suffered by the poorest” (LS 48). We must respond with courage to the “the increasingly desperate cries of the earth and its poor”. 
It is useful to assume that 1.5 ° C is also a religious threshold. The world we are destroying is the gift of God to humanity, precisely that house sanctified by the divine Spirit (Ruah) at the beginning of creation, the place where he pitched his tent among us (cf. Jn 1: 14 ). As Pope Benedict XVI wrote: “The world is not something indifferent, raw material to be utilized simply as we see fit”,  but rather it is God’s creation. In 2001, the American bishops underlined that, “if we harm the atmosphere, we dishonour our Creator and the gift of creation”.  It is a profound truth that we learn above all from our indigenous brothers and sisters: “For them, land is not a commodity but rather a gift from God and from their ancestors who rest there, a sacred space with which they need to interact if they are to maintain their identity and values” (LS 146).
The alarming call of scientists to act to take care of our common home that is coming to pieces is also supported by a very powerful appeal from the young generations, whose future is threatened: “Young people demand change” (LS 13) and there is an active movement of pupils and students rising throughout the world. At World Youth Day in Panama this year, the young launched “Generation Laudato si’” and published a powerful manifesto, which challenges communities of faith and civil society to a radical ecological conversion in action.  They ask us to implement the urgent transition to renewable energy sources in line with the Paris Agreement and put an end to the era of fossil fuels, echoing the appeals of bishops throughout the world.  In recent months, young people have become increasingly explicit, as we see, for example, in the strikes for the environment. Their frustration and anger towards our generation is clear. We risk robbing them of their future, as well as “leaving to coming generations debris, desolation and filth” (LS 161).
It is time to organize an intervention. As stated in Laudato si’, “the effects of the present imbalance can only be reduced by our decisive action, here and now”(LS 161). We will all have to make a radical change in our lifestyle: the use of energy, consumption, transport, industrial production, construction, agriculture, etc. Each of us is called to act. But we must also take action together, starting with governments and institutions, families and people: we need all hands on deck. “Everyone’s talents and involvement are needed” (LS 14) to address this crisis and defeat the powerful interests that hinder our meaningful collective response to this unprecedented threat against our civilization.
It is right to join the scientists and the young in urging our human family, especially those who are in positions of political and economic power, to undertake drastic measures to change course. We must “one world with a common plan” (LS 164). We need to appeal to political leaders to be far more courageous and to listen to the dramatic cry raised by the scientific community and the climate youth movement. “Governments are obliged to honour the commitments they made” in 2015.  World leaders attending the United Nations Summit on Climate next September 2019 must produce solid national plans for the implementation of the Paris Agreement, especially “those countries which are more powerful and pollute the most” (LS 169). To tackle this alarming climate crisis, we need to mobilize will and decision, as well as economic resources on a large scale. It was done during the financial crisis of 2007-2008 to save the banks: is it not possible to do it again now to save our common home, the future of our children and future generations?
There is still hope, great hope, and there is still the time to act and avoid the worst effects of climate changes. “Human beings, while capable of the worst, are also capable of rising above themselves, choosing again what is good, and making a new start” (LS 205). We must “revive” the best resources of our human nature, the innate virtues of love, compassion, generosity and altruism. The greatest resource of man is that the Lord of life does not abandon him, He does not leave him alone, because He is joined definitively with him and with the earth, and His love always leads to finding new roads (see LS 245).
24 May 2019, on the Fourth Anniversary of Pope Francis’ Encyclical Laudato si’
Peter K.A. Cardinal Turkson
 Intergovernmental Panel on Climate Change (IPCC), Special Report on Global Warming of 1.5°C (8 October 2018) (in: https://www.cmcc.it/ipccitalia/ipcc-special-report-global-warming-of-1-5-c/).
 Francis, Address to the participants in the International Conference on the occasion of the third Anniversary of the Encyclical Laudato Si’ (Vatican City), 6 July 2018 (in http://w2.vatican.va/content/francesco/en/speeches/2018/july/documents/papa-francesco_20180706_terzoanniversario-laudatosi.html).
 Benedict XVI, Apostolic Exhortation Sacramentum Caritatis, 22 February 2007, no. 92 (in http://w2.vatican.va/content/benedict-xvi/en/apost_exhortations/documents/hf_ben-xvi_exh_20070222_sacramentum-caritatis.html).
 United States Catholic Bishops’ Conference (USCCB) Global Climate Change: A Plea for Dialogue, Prudence and the Common Good, 15 giugno 2001 (in http://www.usccb.org/issues-and-action/human-life-and-dignity/environment/global-climate-change-a-plea-for-dialogue-prudence-and-the-common-good.cfm).
 World Bishops' Appeal to COP21 Negotiating Parties, October 2015 (https://www.cidse.org/newsroom/press-release-catholic-church-worldwide-calls-for-urgent-climate-action-and-for-a-major-break-through-at-the-cop-21-paris-conference.html).
 Francis, Message for World Day of Prayer for the Care of Creation “Show mercy to our common home”, 1 September 2016 (in http://w2.vatican.va/content/francesco/en/messages/pont-messages/2016/documents/papa-francesco_20160901_messaggio-giornata-cura-creato.html).