It's atmospheric liposuction: a retrospective fix for planetary over-indulgence. Geo-engineering, which means either sucking carbon dioxide out of the atmosphere or trying to shield the planet from the sun's heat, is an admission of failure, a failure to get to grips with climate change. Is it time to admit defeat and check ourselves into the clinic?

The question has arisen again with the launch of a new experiment funded by Britain's Engineering and Physical Sciences Research Council, injecting particles (in this case water droplets) into the atmosphere from a gigantic balloon attached to a hosepipe. The eventual aim, if such experiments are deemed successful, is to squirt large amounts of sulphate aerosols into the stratosphere, to reduce global warming by scattering sunlight back into space.

There are five issues affecting all the proposed geo-engineering technologies. Are they effective? Are they cheap? Are they safe? Do they solve the other problem associated with rising greenhouse gas emissions: ocean acidification? Do they introduce moral hazard? (This means the risk that you'll behave more recklessly if you're insulated from the effects of your actions.)

Broadly speaking, the cheap and effective options are dangerous; the safe options are expensive or useless. This isn't always the case. Seeding the oceans with iron filings, for example, is probably both useless and dangerous. The intention is to stimulate a bloom of algae which absorbs carbon dioxide then sinks to the ocean bed. Not only is little of the gas removed from surface waters by this method; but, because the iron mops up oxygen, it stimulates the production of methane, a potent greenhouse gas. The technique is likely both to damage life in the oceans and cause more global warming than it cures.

There are dozens of proposed techniques. Here's a small sample: Sucking CO2 out of the air using artificial trees. Safe. Effective. Fantastically expensive.

Growing biomass then burying it or dumping it in the sea. Ecologically damaging. Likely to exacerbate famine. Ineffective (because it can't be scaled up sufficiently). Fairly cheap.

Dumping lime or calcium or magnesium silicates into the sea, where they react with carbon dioxide. Fairly safe. Effective. Expensive. Has the advantage of potentially reversing ocean acidification, but the amount of quarrying required to produce enough ground-up rock is likely to be prohibitive.

Painting buildings white to ensure that the earth absorbs less of the sun's heat. Safe. Useless. Expensive.

Whitening clouds to reflect more sunlight, most feasibly by spraying salt water into the air. Middling dangerous. Middling useless. Middling cheap.

Shooting mirrors into space. Not very dangerous. Effective. Staggeringly expensive.

You can read more detailed summaries of these options in a report published by the Royal Society.

But of all techniques, it's the notion of injecting reflective particles into the atmosphere – the technique the balloon and hosepipe experiment is designed to test – that has received most attention. There's an obvious reason for this: it is both cheap and effective. It is also extremely dangerous.

The reason seems almost as incredible as the proposed technologies, but it's rooted in solid science. In fact we've already tested the method at a very large scale, with catastrophic results. Unfortunately no one realised we were running the experiment until three decades after it began.

It wasn't until 2002 that a paper was published linking the great famines of the 1970s and 1980s with atmospheric sulphate particles produced in the northern hemisphere. But the link, which has now been made in a number of papers, listed below, seems to be conclusive:

LD Rotstayn and U Lohmann, 1 August 2002. Tropical Rainfall Trends and the Indirect Aerosol Effect. Journal of Climate, vol 15, pp2103-2116

IM Held, TL Delworth, J Lu, KL Findell, and TR Knutson, 13 December 2005. Simulation of Sahel drought in the 20th and 21st centuries. PNAS, vol 102, no 50, pp17891-17896. DOI: 10.1073/pnas.0509057102 M Biasutti and A Giannini, 8 June 2006. Robust Sahel drying in response to late 20th century forcings. Geophysical Research Letters, vol 33, no 11. DOI: 10.1029/2006GL026067 JE Kristjansson et al, 23 December 2005. Response of the climate system to aerosol direct and indirect forcing: Role of cloud feedbacks. Journal of Geophysical Research – Atmospheres, vol 110, no D24

By reducing the size of the droplets in clouds, thereby ensuring that they reflected more light (which is the desired outcome of the current experiment), the sulphate particles lowered the temperature of the sea's surface in the northern hemisphere. The result was to shift the Intertropical Convergence Zone – a region close to the equator in which moist air rises and condenses into rain – southwards. The Sahel, which covers countries such as Ethiopia, Sudan, Chad, Niger, Burkina Faso and Senegal, is at the northern limits of the zone. As the rain belt was pushed south, the Sahel was left high and dry. As a result of the clean air acts, between 1970 and 1996 sulphur emissions in the US fell by 39%. This appears to have helped the North Atlantic to warm, allowing the rains to return to the Sahel in the 1990s.

The balloon and hosepipe experiment is a complete waste of time. The hazardous effects of injecting particles into the atmosphere are unlikely to make themselves known until the technique is deployed on a very large scale and for several years. The impacts of small-scale tests will be lost in the noise of global weather. A full-scale experiment would be, to say the least, unethical.

As a recent paper in Nature Geoscience points out, it is "physically not feasible" to stabilise global rainfall and temperature by means of this technique while greenhouse gas emissions are still rising. The effects of shooting particles into the atmosphere will vary dramatically in different parts of the world, helping some, harming others. It's impossible to see how the countries likely to be harmed by this technique would agree to it. If it were imposed on them it would lead to the mother of all conflicts – and the mother of all lawsuits.

It is so obvious that this approach is a non-starter that the £1.6m the UK government is spending on the experiment would be better used to investigate those age-old questions of how to turn lead into gold or extract sunshine from cucumbers.

This is not to suggest that we should dismiss all geo-engineering techniques out of hand. But, like liposuction, none of those being proposed are simultaneously safer, cheaper and more effective than addressing the problem at source. This means reducing our greenhouse gases. A good diet and plenty of exercise are better than the knife.