LONDON, Oct 20 (Reuters Breakingviews) - Jakob Stausholm is doing his bit for climate change. Rio Tinto’s (RIO.AX), (RIO.L) chief executive on Wednesday promised the miner would halve its 31.5 million tonnes of annual carbon emissions by 2030, besting rival BHP’s (BHP.AX), (BHPB.L) reduction target of at least 30%. Stausholm also doubled capital investment in metals key to the energy transition. Given the huge gap between currently planned projects and what’s needed read more , that’s a good thing. The trouble is that this is only a small part of Rio’s overall contribution to global warming. Include emissions produced by its customers and the company is responsible for 550 million tonnes of carbon every year. Much of this comes from Chinese steel mills that use Rio’s ore. But rivals like Fortescue Metals (FMG.AX) want to tackle their whole carbon footprint, and Rio and BHP will have to follow at some point. Luckily for Stausholm, shareholders in big miners don’t seem to be clamouring for a speedier approach read more . (By George Hay) On Twitter http://twitter.com/breakingviews Capital Calls - More concise insights on global finance:Apollo, god of basically everything read more DraftKings’ $23 bln UK punt has long odds read more Alibaba cloud has silver lining for Chinese chips read more Klarna rushes to self-regulate before regulation read more Supply-chain crisis may be nearing its peak read more