A group of shipping firms warned that the International Maritime Organization’s planned net zero rules risk imposing significant costs on the industry. The IMO, shipping’s global regulator, has set a goal of net zero for shipping by mid-century and next month aims to formally adopt a plan that would see ships pay levies for at least some of their emissions. The U.S. has criticized the IMO’s Net Zero Framework, labeling it a “global carbon tax.”The sector faces paying about $20 billion to $30 billion a year by 2030, shippers representing more than 1,200 vessels said in a statement dated September 18. The amount could accumulate to more than $300 billion by 2035 if the global fleet misses targets by as little as 10%, they said. The International Chamber of Shipping, which represents more than 80% of the planet’s merchant fleet, also supports the plan.