IPCC wrote: "Reliable cost estimates for these options have not been published"
Well, at least one reliable looking cost estimate has been published for a space sunshade scheme, in this remarkable NASA sponsored work: "Feasibility of cooling the Earth with a cloud of small spacecraft near the inner Lagrange point (L1)" (Roger Angel, Proceedings of the National Academy of Sciences of the USA, Nov 3, 2006) http://www.pnas.org/cgi/reprint/0608163103v1 Considering the seriousness of the study the $4 trillion estimate can't be too far out. This is quite cheap for the hefty insolation reduction (1.8%) and the 50 yr estimated lifetime (only about $80 billion per year). It seems that what's new about this state-of-the-art scheme compared to the earlier proposals listed in the paper is that it requires much less mass so that it could be Earth launched. Cost estimate includes electromagnetic launch from Earth followed by ion propulsion to some point a little sunward of the inner Lagrange point (1.5Gm from Earth on the 150Gm Earth-Sun line). Fascinating reading. I learnt why a refractive screen solution requires only one tenth the total mass of a reflective screen solution for the same overall g/m2. This unfortunately rules out the occasional use as an asteroid deflector I was hoping would be possible I am afraid. Michel ----- Original Message ----- From: "Michel Jullian" <[EMAIL PROTECTED]> To: <vortex-l@eskimo.com> Sent: Sunday, May 06, 2007 6:08 PM Subject: Re: [Vo]:Mitigation of Climate Change IPCC SPM report just out The only mention in the report of planetary engineering solutions is brief, and clearly unenthusiastic: "Geo-engineering options, such as ocean fertilization to remove CO2 directly from the atmosphere, or blocking sunlight by bringing material into the upper atmosphere, remain largely speculative and unproven, and with the risk of unknown side-effects. Reliable cost estimates for these options have not been published (medium agreement, limited evidence) [11.2]" Some of the reasons why the agreement on this statement was only "medium" can be found in this Guardian article: US answer to global warming: smoke and giant space mirrors http://environment.guardian.co.uk/climatechange/story/0,,1999968,00.html#article_continue Michel ----- Original Message ----- From: "Michel Jullian" <[EMAIL PROTECTED]> To: <vortex-l@eskimo.com> Sent: Friday, May 04, 2007 11:48 AM Subject: [Vo]:Mitigation of Climate Change IPCC SPM report just out 35 pages "Summary for Policy Makers" of the IPCC report on Mitigation of Climate Change finalized today in Bangkok has just been posted online: http://www.ipcc.ch/SPM040507.pdf ... A. Introduction 1. The Working Group III contribution to the IPCC Fourth Assessment Report (AR4) focuses on new literature on the scientific, technological, environmental, economic and social aspects of mitigation of climate change, published since the IPCC Third Assessment Report (TAR) and the Special Reports on CO2 Capture and Storage (SRCCS) and on Safeguarding the Ozone Layer and the Global Climate System (SROC). The following summary is organised into five sections after this introduction: 1.. . Greenhouse gas (GHG) emission trends 2.. . Mitigation in the short and medium term, across different economic sectors (until 2030) 3.. . Mitigation in the long-term (beyond 2030) 4.. . Policies, measures and instruments to mitigate climate change 5.. . Sustainable development and climate change mitigation. References to the corresponding chapter sections are indicated at each paragraph in square brackets. An explanation of terms, acronyms and chemical symbols used in this SPM can be found in the glossary to the main report. ... -- Michel
