Danish scientists have reported that an Atlantic current taking tropical water north to the Arctic might collapse by 2050. Others have challenged this. But they reminded me of my only close encounter with the Gulf Stream, which made me realise how fragile our climate was.

Growing up in South Ayrshire, I was intrigued at who I shared the 55th parallel with: Omsk in Siberia, Hudson Bay in northern Canada and somewhere just south of Juneau, Alaska. I was told that the subtropical gardens at Logan and Colonsay were "because of the Gulf Stream" and our relatively temperate climate was due to this mysterious but obviously mighty phenomenon.

Ten years ago I sailed across the Gulf Steam, between Bermuda and Massachusetts. Our instruments showed sea temperature, the warmer the redder. They indicated a red "river" about 3 kilometres wide, gently bending. For sailing it mattered: not only was it moving at 3-4 knots compared with the surrounding sea, but it ran against that day’s wind, a force 8 gale, meaning that it was rough.

But I was more struck by its narrowness. I had assumed a great current hundreds of miles wide must be responsible for warming Scotland. The thin stream on our screen looked capable of wandering off wherever it liked. Unlike the Clyde, there weren’t hills holding it in place.

I felt uncomfortably aware that if we surrounded the Gulf Stream with warmer water than it was used to, alarming effects might follow. Even if the Copenhagen scientists aren’t exactly right, they have highlighted a plausible-looking risk.

We have also seen how fragile our political consensus is for dealing with climate change. A pollution measure unrelated to global warming grabbed politicians’ attention after the Uxbridge by-election, threatening any unpopular climate policy.

I recall, I hope without rose-tinted lenses, how the Blair/Brown partnership – more cohesive on big things than often perceived – identified important, unpopular matters, like climate change and African development. They then created public demand for something to be done: a wave they wanted to ride. All parties went greener. And Michael Howard, entering the 2005 election in this context, adopted the slogan “More Aid, but Better Aid”.

Can we envisage positive competition on these subjects now, when we spend more aid budget on hotel accommodation in the UK than we spend in Africa? And when we focus on keeping migrants and refugees out, regardless of where else they end up, rather than addressing, with partners, why they leave home?

Big issues, like climate change, migration and international development are linked, complicated and not open to quick popular fixes. Addressing them is morally imperative - but also in our interest. Our recent leaders have approached them with few signs of principled consistency, more as in the words of French 19th century radical Alexandre Ledru-Rollin: “There go my people. I must follow them – for I am their leader”.

There are signs that "the people" have surprised focus group-gazing politicians with their real concern about climate. Let’s hope so. And, less optimistically, let’s hope this extends to migration and development.

George Fergusson is a retired senior diplomat