But a more fundamental —and growing—debate is about its relationship with food. Tea growers in Assam and winemakers in France claim temperature changes have altered the taste of their products, and worry that this may lead to more competition, perhaps losses.

And, the World Wide Fund for Nature is pitching for sustainable methods of producing beef, after the Food and Agriculture Organization found that raising animals for milk or meat caused more greenhouse gas emissions than the entire transport industry.

To be sure, the scientific links that back such relationships are still tenuous.

That the debate has progressed nonetheless is a signal of the selling power of climate change. Perhaps, like vegetarians or teetotallers, we shall one day have a set of people who will shun unsustainable food.