Even with taking the necessary action to reduce our CO2 emissions, scientists now know that we can only achieve the Paris goal of limiting warming to 2C or less by also removing CO2 and storing it securely – so-called ‘negative emissions’. With its vast area and great depth, the ocean has been proposed as the ideal storage facility for our problem CO2. What are technical challenges of doing this, and what are the potential hazards along the way? Professor Philip Boyd of UTas will take us into the murky waters of hacking the oceans’ carbon cycle.