In this paper, we examine how to trigger a wave of low-carbon investments compatible with the wellbelow 2°C target of the Paris Agreement in the current post-pandemic context of increasing private and public debt. We argue that one major obstacle to catalyzing global excess savings at sufficient scale and speed on climate mitigation, and to 'greening' economic recovery packages, lies in the upfront risks of low-carbon investment. We then explain why public guarantees should be the preferred risk-sharing instrument to overcome that obstacle. We outline the basic principles of a multilateral sovereign guarantee mechanism able to maximize the leverage effect of public funds and massively redirect global savings towards low-carbon investments, with the double benefit of bridging the infrastructure investment gap in developing countries and reducing tension between developed and developing countries around accelerated funding for low-carbon transitions. We carry out numerical simulations demonstrating how the use of guarantees from AAA-rated sovereigns, calibrated on an agreed-upon 'social value of carbon', is compatible with public-budget constraints of developed countries. In summary, the use of such guarantee mechanisms provides a new form of 'where flexibility', which could turn real-world heterogeneity into a source of reciprocal gains for both developed and developing countries, and contribute to meeting the USD 100 billion + pledge of the Paris Agreement.
Key policy insights

• Catalyzing excess world savings through low-carbon investments (LCIs) would secure a safer and fairer economic recovery from the COVID-19 crisis and avoid locking developing countries into carbon-intensive pathways.
• Public policy instruments focused on creation of public guarantees can reduce the up-front financial risks associated with LCIs, mobilize private money and increase the leverage of public finance.
• A multi-sovereign guarantee mechanism would yield financial support from developed to developing countries in cash grant equivalent and equity inflows two to four times higher than the 'USD 100 billion and more' commitment of the Paris Agreement, and provide greater confidence in meeting this commitment equitably and effectively with benefits for all.