Last September, the United Steelworkers, a major United States labour union, filed a 5,800-page petition to the US Trade Representative accusing China of illegally stimulating its green technology export industry - technologies such as wind power, solar energy, advanced batteries and clean-energy vehicles.
If the US acts aggressively on this complaint, it could become a dispute of wide-ranging and long-term significance.
China could argue that its actions are not merely self-serving but an enactment of its global responsibility. This could put the US in a negative light by comparison. As Zhang Guobao , the head of China's National Energy Administration, put it, if the US brings the case before the World Trade Organisation (WTO), 'the only ones who will be humiliated are themselves'.
The US does appear to be proceeding with great caution. Last month it announced that it was requesting consultations with China at the WTO on one among a list of issues brought by the union - to end 'import substitution subsidies' of wind power. The complaint concerns grants that are contingent on local content requirements, that is, dependent on the grantee using parts and components that are made in China.
This case rests on whether the effect of China's actions is only to protect its local industries against foreign competition, or whether they bring benefits that are shared worldwide.
Under WTO rules, members may adopt trade-related measures aimed at protecting the environment, provided they fulfil conditions to prevent 'the misuse of such measures for protectionist ends'. The US has historically been at the forefront of adopting such trade-related measures. In the 1990s, it banned shrimp imports from countries where shrimp fishermen used nets that harmed endangered sea turtles. As a result, a case was brought before the WTO against the US by India, Malaysia, Pakistan and Thailand.
Little doubt remains that greenhouse gas emissions - chiefly carbon dioxide from fossil fuels - pose a serious risk of global climate change. And economists agree that effective measures to mitigate this risk must include economic incentives to reduce fossil fuel use, either through disincentives such as taxes or caps on its use, or incentives favouring its alternatives.