Politicians must decide on many aspects of our lives governed by science, from climate change to medicine to the food we eat. How do they determine the right course of action? Former government chief scientist and Royal Society president, Lord May, examines the crucial but uneasy relationship between politics and science.
The world today really is very different from that of 50 years ago. To start with, we live longer.
In the 1950s, average life expectancy around the planet was 46 years; today it is 64.
Climate change has been pushed high up the pollitical agenda
There is more food; communications are faster, cheaper and easier.
All this derives from the application of science, which has grown more in the past 50 years than in all previous human history.
And these advances are still accelerating. But as we head further into the new millennium, we increasingly realise that these well-intentioned uses of science have often had unintended adverse consequences.
Witness climate change, environmental degradation and the unsustainable growth in human numbers.
No wonder people worry about possible unintended consequences of emerging technologies such as GM crops and about the ethics of embryonic stem cell research.
Ministers, of course, very rarely have a scientific background themselves. Margaret Thatcher, who trained as a research chemist, was an exception among the ranks of lawyers, trade unionists and business people.
And that means they have to rely heavily on their scientific advisers. The BSE crisis - mad cow disease - gave a dramatic illustration of the problems inherent in this system.
By analogy with scrapie in sheep, which has been around for centuries with no known effects on humans, scientists said that BSE in beef probably posed no risks to the public.
But the political pressure to be absolutely reassuring soon saw the minister for agriculture showing beef was OK by feeding his daughter a hamburger in front of the TV cameras at his local agricultural show.
The BSE crisis exposed cracks in the system, says Lord May
Then in 1995 the first Briton died from a human form of BSE, known as vCJD. Later research pointed to it being linked to eating BSE-contaminated beef.
Professor Sir John Krebs, who became the first head of the Food Standards Agency, believes the BSE crisis was a turning point. He says: "Neither the politicians nor the scientists who were advising them came up smelling of roses.
"There's no doubt that the politicians did adopt a culture of sedation, making soothing noises when that wasn't justified but equally the scientists were put in a position of making reassuring sounds and supporting the politicians in policy judgements."
Motivated by my own experience of the civil service tendency to hold things close to the chest, one of the first things I did after becoming chief scientific adviser was to set out formal guidelines for handling science advice in policy making.
Further developed by my successor, Sir David King, these guidelines say:
- in any scientific issue, seek advice widely, deliberately including dissenting views
- do it all openly
- frankly acknowledge uncertainty
- try to manage potential risks in a proportionate manner, offering choice whenever possible
Many of the political decisions that have to be taken - and sold to the public - involve such an assessment of risk.
Sometimes that gets out of proportion, especially when the media gets its teeth into a story. But you can't judge risk without proper evidence.
And in a recent report, the House of Commons Science and Technology Committee argued that ministers had become a bit too keen to argue that they'd made decisions on the basis of evidence when there wasn't any.
In its inquiry, the Science and Technology Committee found that drugs classification was a case in point.
They discovered that despite many people's gut feelings there is no actual evidence that putting a drug in "Class A" deters criminality. And they were concerned that ministers tried to pretend there was.
The Liberal Democrat MP and committee chairman, Phil Willis, says: "There's no problem at all with a minister saying, for reasons of public confidence, that he wants to put a particular drug in the highest classification.
"But, please, don't let him then say that he has evidence to support that."
In short, it is one thing to set out formal guidelines for making policy decisions but many other issues need to be included in the process.
For a politician, the science - even when certain - is not the only consideration.
In most debates there will be some who hold views about safety or ethical questions based on religious or other ideological beliefs which trump any scientific fact.
Witness fundamentalist religious beliefs that dismiss worries about climate change because "the End of Days is imminent anyway".
Our current UK government has been a world leader in recognising the threat of climate change. But although they have talked the talk admirably, they have been less good at walking the walk.
Politically difficult topics such as nuclear power, measures to reduce energy-consuming over-packaging, or campaigning for international taxation of aviation fuel, have all been evaded.
Ultimately, as science continues to advance offering more and more possibilities, we must learn to do a better job of asking which doors to open and which to leave closed.
We must learn how to conduct democratic debates about political choices on a stage constrained by scientific facts (and made wobbly by scientific uncertainties).
I think the UK is a leader in the early stages of this learning process but we are still in primary school. We owe it to future generations to move on, looking to graduate fast.
Scientists Advise, Ministers Decide will be broadcast on Radio 4 on Thursday, 15 February, at 2100 GMT. You can also listen online for 7 days after that at Radio 4's Listen again page.