The urgent need to strengthen our climate ambitions!

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Today an increasing number of organisations challenge political leaders to strengthen their climate ambitions. Marches for climate, action days, strikes of school children and university students, demonstrations and petitions, legal actions against inactive governments. Together, they urge to mitigate climate change, recognized as a major issue to face to preserve our societies in a functional biosphere and its biodiversity.

We scientists, as a community, acknowledge that this objective can be achieved only by acting quickly and have the responsibility to support these demands to take action. The findings accumulated over decades by cohorts of scientists belonging to a wide range of disciplines, and synthetized by major world’s organizations (IPCC, IPBES…) need to be translated into unprecedented political actions.

This major research effort has provided the unambiguous knowledge on which this growing awareness is based:

  • The surface temperature of the Earth is increasing. The mean temperature is now 1°C higher compared to the period of 1850 – 1900.
  • This warming is almost exclusively the result of human activities through the combustion of fossil fuels, conversion of natural ecosystems in crop lands, agriculture practices, soil degradation …
  • The current 1°C increase already increased the frequency and intensity of extreme climatic events such as heat waves, droughts and floods. The climatic engine is governed by positive feedback loops, and the more the Earth will warm, the more often such events will occur. A temperature increase above 2°C will trigger an additional amplification of this trend.
  • Climate change combined with direct impacts of human activities threaten biodiversity and ecosystem functions. These losses are expected to produce negative feedbacks by weakening the ability of ecosystems to mitigate the effects of climate change.
  • Global warming directly affects human health and will require huge adaptation efforts for agriculture and industry. It will make extensive areas currently densely populated inhospitable to human life.

To limit the increase in temperature to 2°C, the world’s CO2 emissions will need to decrease by 25% in 2030, and by 85% in 2050.

However, CO2 emissions keep increasing from year to year as the political decisions taken to date prove largely insufficient. Even worse, actions currently proposed will not allow keeping global warming below 3°C by the end of this century, a 5°C increase being likely under current trends. The consequences of such a warming on the Earth’s

ecosystems (loss of biodiversity and of ecological functions), and on the functioning of human societies and economy will be enormous. Such consequences will not be reversible, at least not within centuries. We will not have any remediation options if we fail to act now. The current trajectory will cause perturbations of a magnitude that largely exceeds historical changes experienced by humans.

In the face of the accumulated evidence documenting climatic change, we, as a scientific community, have the responsibility to support the current mobilisations. Beyond the necessary individual actions, it is crucial that concrete and structural actions are immediately taken from the local to the global level.

We reaffirm that there is no alternative. The transition towards lower use of energy and towards renewable energy sources has to start immediately. The longer we wait the worse the consequences will be. Limiting the Earth’s warming and its negative effects necessitates radical changes in our current modes of production and consumption at local and global scales. Identifying the key changes required to stop global warming needs the joint collaboration and participation of all stakeholders. For this we will have to take into account the diversity of contexts, ways of life, and wellbeing of all humans in order to keep or improve social equitability. This is an indispensable condition to ensure adhesion by all to this collective effort.

Knowledge and technologies towards a zero-emission society already exist. Current global subsidies still supporting the fossil energy industries currently exceed 500 billion dollars per year and even a partial reassignment of this budget would facilitate the transition towards a more sustainable society. The rapid development of renewable energy sources, of fundamental changes in mobility and transportation, and the preservation or restoration of natural ecosystems and biodiversity, are not only urgently needed actions towards this transition, they are also unprecedented opportunities for positive investments in a large number of activity sectors.

Governments have to seize the political courage to act now. However, without civic pressure, and without intense, thoughtful and continuous mobilisation changes are unlikely. As scientists, we join the current movements and the call to the political leaders and actors. Effective and equitable measures can still preserve a livable future for humans and all other living organisms – provided these measures are taken now!