Because the 2015 Paris Agreement will not prevent dangerous climate change, there is an urgent need to develop an alternative mitigation strategy.

Even if all national commitments are met and technological breakthroughs accelerate the transition to emission-free technologies, the 2°C target will still be overshot due to systemic inertia from existing greenhouse gases, warming oceans, and the decades required to replace existing infrastructure. Compounding factors include: (a) Most policy-makers greatly underestimate the scale, severity and duration of climate change, and the non-linear impacts of lags, feedbacks and tipping points; (b) Although all IPCC mitigation scenarios require the large-scale deployment of climate geoengineering, many methods may not be politically and/or technologically feasible; (c) While most scenarios assume climate overshoot will occur before safe climates are re-established, many human and environmental systems cannot adapt to higher temperatures. Temperatures likely to cause catastrophic and/or irreversible damage pose unacceptable risks.

Developing a viable mitigation strategy will require prioritising research both on climate overshoot risks, and on the relative effectiveness, risks, costs and timelines of potential mitigation methods. Since geoengineering is required to rapidly mitigate dangerous overshoot, the viability and risks of all potential geoengineering methods need to be investigated.

This research is a prerequisite for evaluating the comparative benefits, costs and risks of using, or not using, various forms of mitigation. A risk management plan can then be developed containing mitigation targets that are precise, measurable and attainable, with clear constraints on the magnitude and duration of both climate overshoot risks and mitigation methods.