TCS4F is an initiative by theoretical computer scientists who are concerned about that other major crisis of our time: climate change. We anticipate that the climate crisis will be a defining challenge of the decades to come, that it will require major changes at all levels of society to mitigate the harm that it will cause, and that researchers in theoretical computer science and in database theory, like all other actors, must be part of the solution and not part of the problem.

The TCS4F initiative proposes a manifesto to commit to a reduction of greenhouse gas emissions: following IPCC goals, the objective is to reduce by at least 50% before 2030 relative to pre-2020 levels. The manifesto is more than a simple expression of concern, because it is a pledge with concrete objectives. However, it does not prescribe specific measures, as we believe this discussion is not settled yet and the right steps to take can vary depending on everyone's practices.

The manifesto can be signed by individual researchers (like you, dear reader!), by research groups, and by organizers of conferences and workshops. Currently, over 90 researchers have signed it, including several database theory researchers. The goal of TCS4F is also to start organizing a community of concerned researchers, across theoretical computer science, to think about the issue of climate change and how to adjust what we do, in particular our travel habits.

We need your help to make this initiative a success and help theoretical CS, and database theory, lead the way towards a sustainable, carbon-neutral future:

• If you agree with our concerns and are ready to commit to reducing your carbon footprint, consider signing the manifesto. Signing is open to all researchers in theoretical CS in the broadest possible sense and of course to the whole database theory community.
• Advertise your support of the manifesto (e.g., by putting one of our badges on your webpage). Talk in your research teams and departments about the manifesto, and see if you can gather support for signing the manifesto collectively as a research group.
• If you are involved in conferences and workshops, start a discussion about the carbon footprint of the event, and whether the event could commit to the manifesto's goal. Indeed, as ICDT and SIGMOD/PODS are moving online this year because of the COVID-19 pandemic, it is a good time to discuss how our conferences could evolve towards more sustainable models.
• Spread the word about the issue of climate change and the TCS4F initiative, and encourage discussion of this important challenge in our communities.

As theoretical researchers, we are not used to discussing uncomfortable non-scientific questions like the effects of our activities on the world. However, we believe that the magnitude of the climate crisis obliges us to act now as a community. We are confident that great changes can be achieved if we do not limit our creativity to our specific research areas and also use it to re-think our way to do research.