It was the big speech everyone concerned with climate change was waiting for. Barack Obama, leader of the world’s biggest economy and second biggest carbon emitter (in terms of sources), was going to address tackling climate change head on in a speech to students at Georgetown University.

The omens weren’t great. The Pres’ Climate Action Plan was released hours before the speech and, while it said a lot of the right things, it consisted of a mishmash of worthy but unambitious proposals rather than a coherent strategy. So how would the speech go?

It wasn’t Obama’s oratorial highpoint. Wilting under (appropriately) high temperatures and competing (ironically) with aircraft flying overhead every few minutes, it was half an hour of hard slog for the man they call POTUS. But the content, oh the content, the content was spot on.

• He demolished the case of the climate change deniers – deriding them as “the flat earth society”;
• He reframed a low carbon economy as an economic opportunity for the US, not a threat;
• He played humble – noting that individual States were leading Federal Government and that the latter had to step up;
• He tackled controversial issues such as the Keystone XL pipeline and shale gas head on – saying the former would not go ahead unless it reduced carbon emissions and presenting the latter as a stepping stone to a low carbon economy (controversial but honest);
• He wisely wrapped the whole issue in the Stars and Stripes – making tackling climate change a patriotic duty for a country that takes patriotism very seriously.

The impact of such leadership was instant with shares in coal companies tumbling before he’d started to speak. There was a marked contrast with the situation here in the UK where the plans are arguably much more ambitious, but the leadership is nowhere – and industry is unsure which way to jump.

I’ve long preached that leadership is the key issue in delivering sustainability – and it was great to see a national leader finally step up and lead. Bravo.