We have developed eight core theses alongside each theme of the conference as a central outcome of the conference. These were prepared before by the Scientific Steering Committee and revised in response to the insights gained at the conference. Here we share the before and after theses as developed at the conference. We will work to further refine the theses and include feedback from groups that were not participating in the discussions which might still help to improve and strengthen them.
As part of a discussion at the conference, the need of an overarching thesis on “Why Overshoot” emerged that is now also included as part of the conference outcomes.
Overarching thesis on Overshoot
Global warming above 1.5°C will increase irreversible and unacceptable losses and damages to people, societies and the environment. It is imperative to minimize both the maximum warming and duration of overshoot above 1.5°C to reduce additional risks of human rights violations and causing irreversible social, ecological and earth system changes including transgressing tipping points. This is required by international law and possible by removing CO2 from the atmosphere and further reducing remaining greenhouse emissions.
Eight core themes
| Theme | Ahead of the conference | Conference revision |
| Theme 1: Highest possible mitigation ambition under overshoot | Surpassing 1.5°C must not lead to target relaxation, but rather to doubling down on emission reduction efforts in the near term. | Surpassing 1.5°C doesn’t change anything for required action in the near term. Reduce emissions, not ambitions. |
| Theme 2: CDR: Sustainability constraints and opportunities | There are sustainability and feasibility limits to the amount of CDR we can deploy which can constrain future mitigation strategies and the amount of warming we can reverse. | CDR is indispensable for reducing global temperatures after overshoot, but its potential to reverse warming in a net-negative world is constrained by sustainability, feasibility, and other limits. |
| Theme 3: Earth System responses up to net zero and beyond | The assumption that global warming can be reversed after net zero emissions may be overly optimistic. | The assumption that Earth System responses can be reversed after net zero emissions is overly optimistic. |
| Theme 4: Climate impact (ir)reversibility | Even if global temperatures decline after overshoot, there is no going back for a number of climate impacts. | Even if global temperatures decline after overshoot, there is no going back for a number of biophysical climate impacts, as well as some social, economic, political and cultural systems which could face new risks and vulnerabilities. |
| Theme 5: Overshoot legacy and tipping elements | Overshoot risks triggering tipping points that cannot be stopped by reversing warming, leaving humanity to grapple with irreversible planetary changes for centuries. | Overshoot risks triggering tipping dynamics and cascades that cannot be fully stopped by reversing warming, causing additional and severe planetary changes to climate and the biosphere for centuries, some being irreversible. The only way to mitigate most tipping point risks is to minimize overshoot amplitude and duration. |
| Theme 6: Adaptation,
adaptation limits under overshoot |
Peak warming, not long-term warming outcomes, determine adaptation needs. | The level, timing and duration of overshoot will be a determinant of adaptation limits and will influence the status and functioning of ecological and social systems, along with the effectiveness and costs of adaptation options. |
| Theme 7: Loss and Damage | Losses and harms compound under overshoot requiring Loss-and-Damage responses that integrate human-development modelling, uncertainty, and lived realities. | Losses and harms compound under overshoot requiring Loss-and-Damage responses that integrate human-development modelling, uncertainty, and lived realities. |
| Theme 8: Legal and justice implications of overshoot | Climate overshoot exposes the limits of international law in addressing burden sharing, accountability and reparations, leaving vulnerable communities to face escalating harms and costs. | Climate overshoot exposes the limits of international law in addressing current and future climate harms, entrenching vulnerabilities and increasing injustice. Addressing these limits requires innovation and evolution in legal norms and practice. Scientific evidence can help demonstrate breaches of existing legal obligations and provide compelling reasons for evolution. |