Infinitum Electric, an electric motor maker based in Texas, has attracted $80 million in investment from several major energy-focused firms, enabling it to boost production.

Amazon.com, Exxon Mobil Corp. and Volvo are among more than 700 companies being targeted in a campaign backed by a large group of investors advocating for greater transparency when it comes to environmental impact.

In the debate over climate change, the heaviest polluters — think: power plants, trucks and cars — get the most attention from policymakers. New research suggests a broader view might be called for.