Greenpeace have been strongly criticised in recent weeks over the destruction of a trial crop of genetically engineered wheat. Some critics have labelled the organisation “anti-science” and claim that opposition to GM crops somehow contradicts the support of climate science.

First, it is useful to revisit what “science” actually is, and what it isn’t.

Science is broadly defined as the systematic study of the structure and behaviour of the physical and natural world through observation and experiment. The scientific method involves observing the world, putting forward a hypothesis (theory), and then attempting to disprove that hypothesis. Theories that can’t be disproved become accepted, until they are disproved and replaced by a theory that is more robust.

So, contrary to much popular opinion, science really isn’t about “proof” at all. It is about “disproof”.

In relation to global warming, after many years of observing trends in nature (rising CO2 levels in the ocean and atmosphere, slow but steady increases in global average temperatures, etc.), scientists put forward the theory of “man-made global warming”. Scientists have been trying to disprove this theory, but so far they haven’t succeeded — it remains the best theory to describe what is happening to the global climate system.

What climate deniers and so-called climate sceptics seem to misunderstand amid their attempts to discredit climate science, is that the mainstream scientific process that they are railing against is actually geared around trying to disprove the theory of man-made global warming. The reason that I call them climate deniers rather than climate sceptics is that all climate scientists are sceptical of the theory of global warming as a result of the scientific method they use, but what we see from the deniers is just that — outright denial.

But the scientific method does not stand alone in our decision making about science and technological development. Science is, and must be, guided by values and principles, one of which is the “precautionary principle”. The application of the precautionary principle helps to determine where the burden of proof or the burden of disproof should lie.

In the case of climate change, the burden of proof, or the burden of disproof is clear. There is an obvious trend happening in the world that is widely regarded as potentially dangerous. A theory has been identified to describe what is happening, this theory has withstood enormous scientific scrutiny and is therefore widely accepted by the scientific community with a high level of confidence.  The negative consequences of global warming happening are enormous compared to cost of doing something about it. The burden of proof clearly rests upon climate deniers (or indeed climate scientists) to disprove the theory of human induced global warming. I hope they manage to do it because the implications of global warming are almost too disturbing to contemplate.

In the case of genetically engineered foods however, the issues are less straightforward and reveal the political and values based judgments that are also made as part of the scientific process. But first, it is important to be clear that genetically engineered foods are not science. Nuclear power isn’t science either. Neither are pop-up toasters. They are the commercial products that rely on scientific understanding for their development.

The science involved in genetic engineering is the theory of the genome and the relationships between DNA, RNA and proteins. One of the technological spin-offs of these scientific theories (which thus far have not been disproven) is a technique of inserting genes from one species into the genome of another in order to achieve a beneficial trait in the recipient organism.  The body of scientific evidence suggests that the relationships between DNA, RNA and proteins are extremely complex and the implications of inserting a foreign gene are likely to be many and unpredictable.