ON MARCH 20th Exxon Mobil, surely the world’s least tree-hugging company, became the first oil giant to say it would publish details of its “stranded assets”—the value of oil and gas fields that it might not be able to exploit if there were a high carbon price or tough rules on greenhouse-gas emissions. Giant Exxon is not doing this because it has gone mushy or caved in to green activists. Rather, it is heading off a shareholder resolution by Arjuna Capital, a fund manager, demanding explanations and actions on environmental threats to the firm. Exxon’s decision is the biggest step so far in a wider business trend: companies publishing information on their environmental impact and vulnerability to green regulation, to attract or placate investors.

Until the late 2000s, most firms saw the environment as either irrelevant or a bit of a nuisance. Either way, they did not publish much about it. That has changed drastically. According to CDP, a group that collects environmental data on behalf of investors, more than half the companies listed on the world’s 31 largest stock exchanges publish some environmental data, either in earnings reports, as part of stockmarket listings or voluntarily to CDP itself. In some markets, including the London Stock Exchange and Deutsche Börse, over 80% of large firms publish this sort of data, ranging from their greenhouse-gas emissions to the return on investment of projects which aim to reduce pollution.

Companies that are big sellers of wind turbines and other green-energy products, such as Siemens, need little prompting to report on how green they themselves are. Others have to be told to. America’s Securities and Exchange Commission (SEC) says all firms that file standardised annual reports must include details of climate-change risks that are “material” to earnings. The British government requires large quoted companies based in Britain to disclose their carbon-dioxide emissions to shareholders. And the European Union plans to make firms with more than 500 employees publish environmental and social data in their management accounts—though this proposal, like many emanating from Brussels, may sit gathering dust for years.

But by far the biggest influence on firms comes from investors. They are gathering together and demanding better data. CDP works for investors with $92 trillion in assets—hardly a modest sum. It sends out questionnaires to 5,000 firms asking things such as, “Does your company have emissions-reduction targets?” and “If you do not have any emissions-reduction initiatives, please explain why not.” A network of investors called Principles for Responsible Investment has over 1,000 members with $34 trillion of assets under management. Investors’ main concern is that climate change—or policies to avert it—will damage the firms they invest in, whether they be energy companies with stranded assets, food companies exposed to droughts in Africa or chemicals producers suffering regulatory risk in Europe. As Natasha Lamb, head of equity research at Arjuna, puts it, “Shareholder value is at stake. As investors, we are not throwing good money after bad.”

But to make proper decisions, investors need standardised, comprehensive information that is consistent over time. So far they are not getting it. Ceres, another network of green investors, looked at the green data in SEC filings and concluded that they are poor. Less than two-thirds of insurance companies made any climate-change disclosures in 2012, for instance (and what information they did provide was sketchy). Yet they are more vulnerable to extreme weather than most, paying out $30 billion in claims after Hurricane Sandy hit the United States in 2012.

CDP’s information is better. The firm scores the quality of the data it collects, and the overall scores are rising. Still, there is a big gap between industries that disclose the most (utilities, scoring 91 out of 100) and those which publish the least (oil and gas firms, 78). Patchier still is information from stock-exchange listings. Whereas 80% of firms quoted on some exchanges publish green data, none on the Indonesian and Saudi exchanges does so.

Improving the quality of the data is not easy, partly because firms are loth to publish lots of information unless competitors do, but mainly because institutions are weak. The SEC still gives firms wide discretion on how to interpret its requirement to report green data. Stockmarkets are reluctant to demand much from quoted companies, lest they list somewhere more lenient.

The gold in greenery

Yet releasing good environmental information would be hugely beneficial. True, it is a burden on public companies which private firms would not have to bear. But that burden is not onerous: most green data are cheap to collect, since emissions (for example) are tied to energy usage, which companies track anyway. Better information would help the environment by steering investment away from polluters. And it could be good for companies, too. A study published by Harvard Business School in 2011 looked at 180 firms over 18 years and found that those which paid the most attention to environmental matters also did best when measured by share prices and earnings. This does not prove that greenery causes good performance—more likely, well-run firms pay attention to both—but at least they are not in conflict.

The implications are that there ought to be generally accepted accounting principles for the environment, and that policymakers should pay more attention to efforts under way to create them. The basic framework would not be hard to set: companies should publish assessments of climate risks and opportunities (Exxon is doing that); disclose their greenhouse-gas emissions; and explain how they are seeking to cut them. Investors would benefit; so might the planet.