* Experiment to pump water 1 km into atmosphere dropped
* Concern over lack of governing rules, technology patent
* Test could have given further insight into geo-engineering
LONDON, May 16 (Reuters) - British scientists have abandoned an experiment to test the possibility of spraying particles into the upper atmosphere to stem global warming, largely due to concerns over a patent for some of the technology, the project's leader said.
Scientists and engineers from the universities of Bristol, Cambridge and Oxford are behind a three-year, 1.6 million pound ($2.5 million) geo-engineering project called Stratospheric Particle Injection for Climate Engineering (SPICE).
They had intended to pump water through a 1 km hosepipe into an air balloon to test the engineering design and the effects of wind before scaling up gradually to a potential full-scale balloon project, 20 km high, that would use sulphates and aerosol particles instead of water.
"The decision to call off the experiment was made by all the project partners in agreement," Matt Watson, lead scientist on the SPICE project, said on Wednesday.
The overall project, funded by UK research councils, will continue with its aim to assess the feasibility of so-called solar radiation management (SRM) by mimicking volcanoes when they erupt, which can have both a cooling and warming effect on the earth's atmosphere.
SRM works on the assumption that some eruptions expel particles into the upper atmosphere, bouncing some of the sun's energy back into space and thereby cooling the earth.
The controversial experiment had already been pushed back in October last year for six months due to the need for further public consultation.
Supporters say research into geo-engineering schemes - like aerosol injection, mirrors in space to deflect the sun and giant devices to trap carbon dioxide - is needed as the world might need temporary fixes in the future to tackle the dangerous impacts of climate change.
Most such solutions are decades away from being established at large scale. Critics say they are too costly, potentially harmful, have no international rules governing them and they divert attention from measures to cut greenhouse gas emissions.
LACK OF RULES
Watson said one reason for the cancellation was the lack of rules governing such geoengineering experiments.
"Most experts agree that governance architecture is needed and to me personally, a technology demonstrator, even a benign 1/20 scale model feels somewhat premature," he said, adding that the views expressed were his own.
Another reason was a patent application, describing some of the technology, which was filed before the SPICE project was proposed. UK funding bodies require those applying for grants to declare potential conflicts of interest.
"The details of this application were only reported to the project team a year into the project lifetime and caused many members, including me, significant discomfort," he said.
Although the bigger project will continue in the laboratory, other scientists were disappointed by the cancellation of the balloon experiment as it could have provided further insight into the feasibility of SRM.
"The vast majority of the proposed SPICE experiment is critical research that will help us understand the potential utility and possible dangers of geoengineering with aerosols. It is very important that this research continues," said Jane Long, at the U.S.-based Lawrence Livermore National Laboratory. (Editing by Anthony Barker)