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To what extent is geo-engineering the solution to the climate change problem? Brian Hoskins Director, Grantham Institute for Climate Change Imperial College & Professor of Meteorology, University of Reading Temperature and greenhouse gases in past 650,000 y nitrous oxide carbon dioxide methane proxy for temp time today IPCC 2007 Causes of the current imbalance in the energy budget IPCC 2007 Intergovernmental Panel on Climate Change Fourth Assessment Report (2007): “Global Warming is unequivocal” Estimates of NH temperatures in the past 1000 years Since 1970, rise in: Global surface temperatures Tropospheric temperatures Global ocean temperatures Global sea level Water vapour Rainfall intensity Precipitation in extratropics Hurricane intensity Drought Extreme high temperatures Heat waves Decrease in: NH Snow extent Arctic sea ice Glaciers Cold temperatures Estimates of impacts in different sectors for increasing global warming (IPCC 2007) Tackling the anthropogenic climate change problem By emitting greenhouse gases to the atmosphere we are perturbing the climate system in a dangerous way. What can we do? 1. Adapt to whatever happens: adaptation 2. Move towards a drastic reduction of the emissions of greenhouse gases: mitigation 3. Do something else to compensate: geoengineering Two basic kinds of geo-engineering 1. Reduce the content of greenhouse gases in the atmosphere 2. Alter the climate system Geo-engineering 2 1. Reduce the atmospheric greenhouse gas content plant trees develop & grow special biological organisms fertilise the oceans Oceanic carbon cycle Biological activity in the ocean SeaWiFS Project, NASA/Goddard Space Flight Center, and ORBIMAGE. Geo-engineering 2 2. Alter the climate system Restore the global energy balance by the management of solar radiation In terms of the global energy budget a reduction of the solar energy absorbed in the climate system by about 2% might balance a doubling of atmospheric carbon dioxide The Earth’s energy budget 1 2 3 4 Kiehl and Trenberth 1997 1. In Space: Solar Interceptor At a point where gravitational and centrifugal forces are in equilibrium (Lagrange point) Cloud of many small independent spacecraft. Each one has small solar sails to set its orientation to face the sun and to stay within the cloud, in line with sun (Angell, 2007) 1-year later Eruption Reduction in radiation 2. In the stratosphere, mimicking a volcanic eruption e. g. Mount Pinatubo in 1991 Pitari and Mancini (2002) Proposal: put SO2 at about 25km in the equatorial region 3. Increase the reflection by low-level cloud Average amount of low-level (stratocumulus) cloud 3. Spray Turbine – Concept Latham Salter (2006) 4.Increase the reflectivity (albedo) of the surface 1. Whiten the deserts 2. Enhance reflectivity of human settlements 3. Develop & use more reflective grasses Management of net Solar Radiation: Opportunities at 4 levels in the atmosphere Solar Radiation Solar Interceptor Top of Atmosphere Aerosol Scattering Cloud Albedo SurfaceGrassland, Urbanization and Desert Albedo Level 1 – Space Level 2 – Stratosphere Level 3 – Troposphere Level 4 Surface Comments: 1. The restored energy balance through a reduction in solar radiation would be only in the annual and global average, not in a particular region or time of year 2. Solar and thermal radiation act on the climate system in different ways 3. Increasing acidification of the ocean would continue 4. Feasibility, cost, unintended impacts Discussion 1. Our understanding of likely climate change due to increased greenhouse gases is limited. In general it is more so for geo-engineering “solutions” . 2. Need to be able to evaluate the actual impacts 3. Ability to stop quickly is an important consideration 4. Some private companies are already planning to start ocean fertilisation on a commercial basis, offering it as an off-setting mechanism 5. Is it a “solution”? Is it possible to compensate for any increase in atmospheric greenhouse gases? 6. Necessity for legal and political framework 7. Might it take the pressure off the imperative to reduce greenhouse gas emissions? 8. Is it a good way of buying time until serious greenhouse gas emission reductions have been agreed and executed? Stabilisation CO2 Concentrations and Emissions CO2-equivalent concentration (ppm) Global mean temperature increase above pre-industrial level at equilibrium* (ºC) Peaking year for CO2 emissions Global change in CO2 emissions in 2050 (% of 2000 emissions) 350 – 400 445 – 490 2.0 – 2.4 2000 – 2015 -50 to -85 400 – 440 490 – 535 2.4 – 2.8 2000 – 2020 -30 to -60 440 – 485 535 – 590 2.8 – 3.2 2010 – 2030 +5 to -30 485 – 570 590 – 710 3.2 – 4.0 2020 – 2060 +10 to +60 570 – 660 710 – 855 4.0 – 4.9 2050 – 2080 +25 to +85 660 – 790 855 – 1 130 4.9 – 6.1 2060 – 2090 +90 to +140 CO2 concentration (ppm) * Based on the “best estimate” of climate sensitivity. Source: IPCC (2007). © OECD/IEA 2007 Possible CO2 Emissions for 450ppm Stabilisation 45 Energy-Related CO2 Emissions 42 Gt CCS in industry CCS in power generation Nuclear Renewables Switching from coal to gas End Use electricity efficiency Reference Scenario 40 Gt of CO2 35 30 25 End Use fuel efficiency 27 Gt 450 Stabilisation Case 20 23 Gt 15 10 2005 2010 2015 2020 2025 2030 By 2030, emissions are reduced to some 23 Gt, a reduction of 19 Gt compared with the Reference Scenario © OECD/IEA 2007 Stratospheric Circulation and Ozone distribution Proposal: put SO2 at about 25km in the equatorial region