Two events — one that has just happened and one that may be imminent — are swelling the ranks of investors willing to bet that a great environmental rehabilitation in smog-choked China will become a stock market megatrend.

First came last week’s decision by Donald Trump to pull the US out of the Paris climate accord, ceding leadership over the global green agenda to China and Europe. Then there is the prospect of MSCI, the index provider, deciding this month to include some Chinese A shares into one of its benchmarks for the first time.

“What the Chinese dream about is blue sky and blue water,” says Karine Hirn, partner at East Capital, an emerging market asset manager. “Investment into the global leaders in environmental protection is very exciting.”