Fact check: Is Sadiq Khan right about fires?

Will global warming condemn Britain to more fires? Sadiq Khan, Mayor of London, has been widely quoted this morning comparing recent fires around the capital to the Blitz. ‘Yesterday was the busiest day for the fire service in London since the second world war,’ he said – climate change caused the heatwave which ‘led to the fires’. He added that he was dismayed that the Tory leadership contenders were not discussing this ‘elephant in the room.’

So is this right – or misleading? As so often, it’s a mixture. Khan is correct to say that the number of calls to London fire brigade was a record high: it received more than 2,600 calls. But 999 call handlers can receive hundreds of calls about the same incident. Yesterday the fire brigade responded to 1,146 ‘incidents’ – again the most on record but only slightly above the previous high of 1,058. The records don’t go back before 2009 so how likely is it that 1,146 incidents – almost four times the average – is a postwar high?

But the link between fires and climate change? That’s harder, and more context is needed. The planet is certainly warming, but fires in London are becoming (a lot) less common. So the events accompanying this heatwave need to be put in context. Global land temperatures have taken off since 1950:

But one thing thats not risen is fires in the capital. With the decline of chimneys and chip pans (and the rise of sprinklers and smoke alarms) there are way fewer fires in London – which is why the fire brigade is far smaller than it once was and so many former fire stations are now pizzerias. The planet has been warming but fires have been less frequent.

Our data starts in 1966 and every year from then to 2008 there were more than 30,000 fires in Greater London. Since then they’ve decreased drastically. Fires peaked in 1976 when there were 63,524 fires. Last year there were less than 15,000 – a 77 per cent fall. 

But what about grass fires? The sort seen around London now? The above chart lets you look at secondary fires: grass fires, etc. Usually outdoor and more likely in ‘hot dry summers’ – are, in the words of the London Fire Brigade  'significantly lower than a decade ago’. Why should this be if, as Khan suggests, they are linked with global warming? In 2011 there were some 14,000 such fires, last year the count more than halved to 6,600. These fires peaked in 2003, they’ve fallen 83 per cent since then.

London is particularly good at preventing fires in the first place (the fire service is great at dispensing such advice). Home Office data shows that, despite the capital’s growing population, fires per head have consistently been lower in Greater London than other metropolitan areas since 2001. Last year there were three times as many fires per head in Tyne and Wear than in London (4.7 vs 1.6 per 1,000 people). All over, you can see the trend: far fewer fires.

The data doesn’t go back to the 1940s but if it did, you’d likely see even more fires in a city that was fuelled by more dangerous cooking and heating solutions. Khan is unlikely to provide data showing that the actual number of fires right now compares to the postwar 1940s let alone the blitz. So perhaps there were more phone calls. But yesterday marking a postwar record for actual fires? Really? 

Heatwaves matter. The London Fire Brigade points out that ‘those years where the number of fires were at their highest coincide with the years with notably hot summers with continuous dry periods’ and all of the UK's ten warmest years on record have happened in the last 20 years. It may well be that as Britain’s climate rises it might increase the potential for fires. But what's missed is how adaptable we’ve proved to be: even in those years with temperature records, the total number of fires fell year-on-year in every single year bar one.

The climate challenge raises very serious questions – but we do need to distinguish between the trauma of heatwave and long-term trends. Fires are trending down, in spite of temperature trending up – not quite the impression that Khan gave.