For two days the hallowed halls of the Royal Society in London have been filled with uncomfortable-looking climate scientists. But this is not another "climategate" inquiry, it's a meeting on geo-engineering – proposals to deploy global-scale technologies to control the planet's climate.

For the most part, these technologies don't yet exist. But as time ticks by and greenhouse gas emissions continue to rise, scientists are starting to take geo-engineering seriously. Proposals range from sunlight-reflecting mirrors in space to machines that can scrub carbon dioxide from the air to the seeding of algal blooms in the oceans, which suck carbon dioxide down to the sea bed and keep it there.

The level of scientific uncertainty around geo-engineering is formidable: fears of unintended side effects and irreversible interventions loom large in researchers' minds. Scientists being scientists, they're keen to plug the gaps in their knowledge – but they don't look all that happy about it.

The problem is that proposals to geo-engineer the climate come loaded with social and ethical concerns. Is it acceptable to intentionally intervene in the volatile climate system? How would it be governed? What would prevent the abuse of climate-controlling technologies, and whose hand would be on the global thermostat?

The growing number of scientists working on different aspects of geo-engineering research – from climate modelling, to lab experiments with reflective particles that could be injected into the stratosphere – are anxious to emphasise that they are not geo-engineering cheerleaders. They simply want to understand the pros and cons of different technologies, in case the day came when they might be needed, a day they hope will never come.

The Royal Society itself has taken great care to indicate that it does not advocate geo-engineering – and certainly not in the place of deep global cuts in greenhouse gases. But it does advocate research on geo-engineering, and that's where the dilemma for many scientists kicks in.

On the one hand, it is clearly prudent to understand more about geo-engineering – the worst of all scenarios would involve a government deploying a technology without knowing what its effects would be. Initial evidence suggests that spraying the skies with reflective particles of sulphate would have a major impact on patterns of rainfall. Surely it is better to know this sooner rather than later?

On the other hand, conducting research on geo-engineering is one of the main factors that will make the deployment of the technologies more likely. Most scientists are deeply sceptical about the use of such "remedial" action on global warming. But scientists won't be the ones to decide whether the technology is used. So are they unwittingly clearing the path for future deployment?

Of course, research should help to rule out the craziest of the geo-engineering proposals. Basic research might mean certain dangerous ideas are rejected - and already there is evidence that fertilising the oceans would be a highly risky undertaking. This is valuable knowledge. But there is a danger that the very fact that research is taking place will send out a signal to politicians: there is an alternative to cutting carbon.

For some, the process is eerily reminiscent of the race to develop nuclear weapons in the 1940s. While it might seem alarmist to compare geo-engineering to the quest for nuclear capability, the parallels are striking: both involve novel, uncertain and hugely powerful technologies deployed for the purposes of defence against a threat, both are mired in ethical controversy, and both have an undercurrent of inevitability driving them along.

The Manhattan Project co-opted science to advance military aims. Preventing dangerous climate change is a much nobler endeavour, but the social and ethical implications of geo-engineering the climate are so profound that the scientists involved are caught in an unenviable dilemma. Can this research exist independently of deployment, or is their work ushering in an era of climate intervention that they openly caution against?

• Adam Corner is a psychologist at Cardiff University