Ban Ki-moon calls for clear governance rules for geoengineering based on inclusive, multilateral engagement, and warns against complacency in the face of the unforeseen and unintended consequences of these new technologies. First published in Project Syndicate.

Climate change poses an unprecedented threat to humanity, one that appears increasingly likely to reduce global standards of living dramatically within our lifetime, and cause untold damage in the longer term. And, because addressing such a daunting planetary challenge requires radical approaches, there have been wide-ranging discussions about what the world must urgently do to limit the rise in global temperature to less than 1.5°C above pre-industrial levels.

Although reducing emissions of greenhouse gases must remain the highest priority, the United Nations’ Intergovernmental Panel on Climate Change (IPCC) says this is not enough. Some now suggest that we also need to remove huge amounts of carbon dioxide from the air. Others argue that we may also need to reflect sunlight back into space, to buy the world more time to reduce and remove emissions.

Taken together, these two approaches are known as geoengineering. And as the effects of climate change worsen, a growing number of policymakers, scientists, and entrepreneurs are considering such options more seriously.

But at present, we have no idea what unforeseen and unintended consequences deploying these new technologies might have. Their unknown unknowns – especially with solar geoengineering - could be just as bad as the known challenges presented by climate change.

What’s more, as with global warming, the impact of these technologies will transcend national borders. This puts those who have the least say – the vulnerable and the poor – on the front line. It also risks exacerbating wider threats to international peace and security, such as resource scarcity and forced climate migration.

This is why The Elders, a group of independent global leaders, is calling on the international community to agree on a rigorous governance framework for geoengineering, and to put it in place without delay. Such a decision-making system must be transparent, participatory, and accountable. It should include the voices of those most affected and enable all governments and non-governmental stakeholders to gain the fullest possible understanding of these new technologies for more informed decision-making.

Since the Industrial Revolution, we have known that technology is not a panacea, and that it advances human wellbeing only if all those affected are given the chance to participate in its development. This consideration is all especially relevant to geoengineering, because our knowledge of these technologies and their impact remains limited.

Fortunately, efforts are underway to address this. This week, the UN Environment Assembly – the world’s highest-level decision-making body on environmental issues – will consider whether to initiate a global learning process on both the science and governance of geoengineering. To this end, the UNEA would call for a worldwide assessment of these emerging technologies, giving all countries a common platform of knowledge.

This shared understanding is an important first step toward ensuring that decisions concerning the use or non-use of geoengineering are based on the principles of equality, justice, and universal rights. These are the values underlying the 2015 Paris climate agreement and the Sustainable Development Goals, both of which were adopted during my tenure as UN Secretary-General.

The UN is best placed to accommodate the governance frameworks requirements we now need. Only through the UN’s multilateral processes can we ensure that geoengineering technologies, and how they might be applied, are not the preserve of individual states. This is vital for environmental sustainability, international security, and the wellbeing of future generations around the world.

Many people are wary of this debate, particularly in international fora. They fear that it could be a foot in the door for highly dangerous ideas, and that the very act of drawing attention to these technologies could reduce pressure to cut emissions.

I understand these concerns, and I agree that our main collective priority must still be to cut emissions, end the use of fossil fuels, and promote a zero-carbon, climate-resilient, and people-centered economic transition.

But we also need to acknowledge that the geoengineering genie is already out of the bottle. The likelihood of unilateral deployment of solar geoengineering increases every year. The global community must decide whether to engage now, by setting clear governance rules and guardrails, or allow individual actors to take the lead, creating a fait accompli for the rest of us.

Ignoring this debate would be a mistake. Instead, the world should focus on learning more, including via the process at the UNEA, in order to understand the full range of options and assess their risks with the best information available.

How to understand and potentially harness disruptive new technologies for the benefit of all humanity is one of the defining questions of our age. Future generations will not forgive us if we fail to answer it convincingly.