Graeme MacDonald Taylor , Sue Vink 

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

Even if most countries greatly increase their commitments 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 risks are: (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 feasible 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 both carbon removal geoengineering and solar geoengineering will be required to rapidly mitigate dangerous climate change, 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 realistic 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.