An article in the Telegraph by Louise Gray carries the headline, "Cancun climate change summit: UN considers putting mirrors in space" [LINK]. That is a misleading headline, to put it mildly. What is really happening is that there's another "climate summit" happening now in Cancun, just like last year at Copenhagen. The difference with Cancun is that there aren't any expectations; for some reason people had high hopes for a deal at Copenhagen despite all the indications that it would not happen. This article, however, isn't really about the summit, it seems to be about the talk that Rajendra Pachauri (head of IPCC) gave at the summit. I haven't double checked, but it sounds like he gave an overview of the current IPCC endeavor, gearing up for the Fifth Assessment Report (AR5), which will be released in 2014-ish. What's with the mirrors, though? Well, the AR5 is going to change structure a little bit, just like all the other reports have done. New chapters are going to be added, for example dealing with clouds and aerosols (coverage of clouds and aerosols has been spread across several chapters in the past). The mirrors are a geoengineering idea, and for the first time geoengineering is going to be dealt with explicitly in the IPCC assessment. There won't be a separate report about it, nor even a separate chapter. Like other topics that have emerged in previous reports, geoengineering will be sprinkled throughout the AR5. Specifically, there are sections in the carbon/biogeochemistry chapter (Ch. 6), cloud/aerosol chapter (Ch. 7), the near-term climate change chapter (Ch. 11) in Working Group 1 (physical science basis), plus part of Ch. 5 in WG3's report. This was all laid out already by the IPCC and is available on their web site [LINK].
This was all just to criticize the coverage by the Telegraph. The "UN" isn't considering geoengineering implementation, as the story might lead you to believe. The fact is that research, serious research, is now being done to understand the consequences of geoengineering ideas. Since the AR5 is assessment of climate change science, it is natural to include these geoengineering results. The IPCC is not going to recommend putting mirrors in space.