Lighter-coloured crops, aerosols in the stratosphere and iron filings in the ocean are among the measures being considered by leading scientists for "geo-engineering" the Earth's climate, leaked documents from the UN climate science body show.

In a move that suggests the UN and rich countries are despairing of reaching agreement by consensus at global climate talks, the US, British and other western scientists will outline a series of ideas to manipulate the world's climate to reduce carbon emissions. But they accept that even though the ideas could theoretically work, they might equally have unintended and even irreversible consequences.

The papers, leaked from inside the Intergovernmental Panel on Climate Change (IPCC), ahead of a geo-engineering expert group meeting in Lima in Peru next week, show that around 60 scientists will propose or try to assess a range of radical measures, including:

• blasting sulphate aerosols into the stratosphere to reflect sunlight into space;

• depositing massive quantities of iron filings into the oceans;

• bio-engineering crops to be a lighter colour to reflect sunlight; and

• suppressing cirrus clouds.

Other proposals likely to be suggested include spraying sea water into clouds to reflect sunlight away from the Earth, burying charcoal, painting streets and roofs white on a vast scale, adding lime to oceans and finding different ways to suck greenhouse gases out of the air and deposit heat deep into oceans.

The meeting is expected to provide governments with a scientific assessment of geo-engineering technologies, but is widely expected to be in favour of more research and possibly large-scale experimentation despite an international moratorium adopted by the UN last year in Japan.

This week, more than 125 environment, development and human rights groups from 40 countries published a letter sent to Rajendra Pachauri, the Nobel prize-winning head of the IPCC, warning that the body had no mandate to consider the legality or political suitability of using geo-engineering.

"Asking a group of geo-engineering scientists if more research should be done is like asking bears if they would like honey," said the letter, signed by groups including Friends of the Earth International, Via Campesina and ETC.

Concern over the IPCC meeting centres on who should decide what kind of geo-engineering takes place, and how it should be regulated and monitored. Some projects might, if they work, unintentionally change weather patterns and possibly affect farming and livelihoods in some of the most vulnerable areas in the world.

"[Geo-engineering] is not a scientific question, it is a political one. International peasant organisations, indigenous peoples and social movements have all expressed outright opposition to such measures as a false solution to the climate crisis," says the letter.

Britain is, along with the US, strongly backing geo-engineering research and has supported scientists with millions of pounds of university research, including a Bristol University plan to develop a "hose" held up by balloons through which sulphates can be sent into the stratosphere. The Royal Society is now trying to develop international guidelines and principles and is holding workshops around the world.

In a letter to the Guardian this week, Georgina Mace, professor of conservation science at Imperial College, London and Catherine Redgwell, professor of international law at UCL, said that investment in geo-engineering research had already begun and, "without international governance structures, schemes could soon be implemented unencumbered by the safeguards needed".

But according to abstracts of the papers, Redgwell will advise the IPCC in Peru next week that no new laws should be adopted. "A multilateral geo-engineering treaty is not likely or desirable. The appetite for climate change law-making is low."

The main principles, she suggests, should be that geo-engineering is a "public good", there should be public participation in schemes and independent assessment of the impacts.

"Geo-engineering is not a public good but could be a giant international scandal with devastating consequences on the poor," said Diana Bronson, researcher with international NGO the ETC Group.

In the papers, many of the scientists accept there are that major uncertainties around the technologies. However, the scientific steering group of the meeting, which will assess the technologies, includes many well-known geo-engineering advocates who have called for public funds to conduct large-scale experiments as well as scientists who have patents on geo-engineering technologies or financial interests in the technologies.

The meeting has been given added weight because last week, Christiana Figueres, head of the UNFCCC, told the Guardian that the world may have to investigate geo-engineering because emissions were continuing to rise.

"We are putting ourselves in a scenario where we will have to develop more powerful technologies to capture emissions out of the atmosphere", she said. "We are getting into very risky territory."