The current climate response remains heavily concentrated on reducing greenhouse-gas emissions, with carbon removal increasingly recognised as a necessary second component. But the pace of warming, the growing evidence of non-linear Earth-system change, and the risk of crossing further tipping points raise a harder question: whether those two measures can act quickly enough to prevent severe and potentially irreversible impacts. If they cannot, then climate policy also needs to consider a third area of work — carefully governed research into interventions that could exert a temporary cooling influence while emissions decline and atmospheric carbon is drawn down.
The Case For Applied Cooling Research
- Climate risks are cascading, non-linear and underestimated. Tipping points are happening faster than forecast; some have already occurred at less than the current 1.5°C of warming. Several more will likely be triggered in a short period of time.
- To provide maximum protection for the places and peoples we care about requires returning to a climate similar to the relatively stable Holocene conditions of the last 9000 years when carbon dioxide levels did not exceed 280 ppm prior to 1900.
- A “three levers” approach — “reduce, remove and repair” is required:
○ Reducing emissions to zero at emergency speed;
○ Removing carbon by drawdown to return atmospheric conditions to the Holocene zone; and
○ Urgent research to identify safe interventions that cool and protect and repair vital systems and, in the shorter term, aim to prevent warming reaching a level that triggers a cascade of calamitous tipping points that are irreversible on human timescales. - The harsh reality is that the first two levers alone — zero emissions and drawdown — are not sufficient to stop the Earth system charging passing 1.5°C, nor 2°C in all likelihood, regardless of the emissions path.
- Even if the world moves to zero emissions, and CO2levels start to decrease by natural processes and by CO2removal, albedo modification to create active cooling for a limited period may flatten the level of peak warming — and perhaps help avoid existential climate impacts and extreme damage — until the other processes fully kick in.
- Stratospheric aerosol injection (SAI) is presently the most studied and highly scalable option for exerting a near-term, counter-acting cooling influence. As important as computational models are, systematic evaluation of these urgently needed technologies requires experiments in real world conditions.
- Several other proposed approaches also have the potential to be both effective and scalable to exert substantial global cooling influence. These approaches are worthy of intensified investigation.
- We call for developing a credible response to accelerating climate change by augmenting current emission-reduction and carbon removal efforts with an immediate initiation of transparent, applied-science testing and piloting of promising approaches for exerting a near-term global cooling influence.
- Governments should initiate specific cooling research funding projects, and cooperate in doing so.
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