Here comes the science bit

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In science, no work is completed until it has been picked to pieces

Dangerous dithering.

What does a scientist have to do to convince you? The answer used to be “wait until his critics die” – hence the physicist Max Planck’s assertion that science advances one funeral at a time.

But sometimes even that is not enough. Late last month, the smell researcher Luca Turin published striking new evidence supporting an idea first put forward by Sir Malcolm Dyson in 1938. Dyson presented his “vibrational” theory of how our sense of smell works to universal apathy. Three generations later, scientists are still saying “meh”.

That year, 1938, was also when it was first argued that pumping carbon dioxide into the atmosphere would raise global temperatures. The idea came from the steam engineer Guy Stewart Callendar; the broad response was “implausible”. Today, in 2013, scientists have shifted: they generally agree that Callendar was right. Yet there remains a dangerous level of disagreement about the detail.

At least Turin’s scientific peers have presented him with a clear path to follow. Dyson’s idea was that when a molecule gets up our nose, its characteristic smell is created by the way the bonds within that molecule vibrate. In a clever piece of experimental work, Turin has shown that human beings can distinguish between two molecules that differ only in the way they vibrate. The two molecules tested were both cyclopentadecanone, but while one contained normal hydrogen atoms the other contained “deuterated” hydrogen, which has an added neutron in its atomic nucleus. The additional particle creates a difference in the way the molecules vibrate. And that is why, according to Turin, they smell different to us.

The experiment punches a hole in the accepted theory of smell, which says that smell experiences are triggered by differently shaped molecules fitting different receptors in the nose. This “lock and key” idea can’t explain why two identically shaped molecules smell different. But Turin’s critics said last month that before they will even consider accepting his theory, they want him to show exactly what goes on in human smell receptors.

They are right to make such demands. This is science, where no work is finished until it has been picked to pieces. But that is exactly why it has been so easy to do so little about climate change since 1938. Later this year, the Intergovernmental Panel on Climate Change will make some highly equivocal, backtracking announcements. In a report due for release in December, the IPCC will concede that we can’t be sure tropical cyclones will become more frequent, or that droughts will get worse. Worries that the Gulf Stream will collapse, tentatively raised in the 2007 IPCC report, are allayed: such an event is “unlikely” to occur in the foreseeable future.

Concern over details can have an unhelpful effect, masking the big picture on climate change – the one that Nicholas Stern, who wrote the UK government’s 2006 review on the science, said at Davos last month is “far, far worse” than we were led to believe originally. Until that, rather than the detail, becomes the focus, we can continue to dither over whether to do anything, let alone deciding what course we might take.

It does not matter a great deal that no one is willing to risk his career by backing Luca Turin – but to wait for absolute certainty over the details of climate change before we do anything about it will spell life or death for many. If science continues to advance one funeral at a time, its acceleration is assured; and there will be no shortage of funerals in a world that’s 4° warmer.