Global Warming is unequivocal - Imperial College London

1、To what extent is geo-engineering the solution to the climate change problem?Brian HoskinsDirector, Grantham Institute for Climate ChangeImperial College& Professor of Meteorology, University of Reading“Greenhouse” gases determine height of layer from which heat escapesMore greenhouse gases: hig

2、her levelcolder temperatureless heat lostglobal warming (water vapour) carbon dioxide, methane,Temperature and greenhouse gases in past 650,000 yproxy for tempmethanecarbon dioxidenitrous oxidetodaytimeIPCC 2007Causes of the current imbalance in the energy budgetIPCC 2007Since 1970, rise in:Decrease

3、 in: v Global surface temperatures NH Snow extentv Tropospheric temperatures Arctic sea icev Global ocean temperaturesGlaciersv Global sea levelCold temperaturesv Water vapour v Rainfall intensityv Precipitation in extratropicsv Hurricane intensityv Droughtv Extreme high temperaturesv Heat wavesInte

4、rgovernmental Panel on Climate Change Intergovernmental Panel on Climate Change Fourth Assessment Report (2007): Fourth Assessment Report (2007): “Global Warming is unequivocal”“Global Warming is unequivocal”Estimates of NH temperatures in the past 1000 yearsProjections of globally averaged surface

5、warmingProjections of globally averaged surface warmingIPCC 2007Different scenariosIPCC (2007) Surface Temperature Projections IPCC (2007) Surface Temperature Projections 2020s & 2090s relative to 1980-992020s & 2090s relative to 1980-992020s2090sEstimates of impacts in different sectors for

6、 increasing global warming (IPCC 2007)Tackling the anthropogenic climate change problemBy emitting greenhouse gases to the atmosphere we are perturbing the climate system in a dangerous way. What can we do? Adapt to whatever happens: adaptation Move towards a drastic reduction of the emissions of gr

7、eenhouse gases: mitigation1.Do something else to compensate: geo-engineeringTwo basic kinds of geo-engineeringReduce the content of greenhouse gases in the atmosphereAlter the climate systemGeo-engineering 2Reduce the atmospheric greenhouse gas contentplant treesdevelop & grow special biological

8、 organismsfertilise the oceansOceanic carbon cycleOceanic carbon cycleSeaWiFS Project, NASA/Goddard Space Flight Center, and ORBIMAGE.Biological activity in the oceanGeo-engineering 22. Alter the climate systemRestore the global energy balance by the management of solar radiationIn terms of the glob

9、al energy budget a reduction of the solar energy absorbed in the climate system by about 2% might balance a doubling of atmospheric carbon dioxideKiehl and Trenberth 1997The Earths energy budgetThe Earths energy budget12341. In Space: Solar Interceptor1. In Space: Solar InterceptorCloud of many smal

10、l 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)At a point where gravitational and centrifugal forces are in equilibrium (Lagrange point)2. In the stratosphere, mimicking a volcanic eruption 2

11、. In the stratosphere, mimicking a volcanic eruption e. g. Mount Pinatubo in 1991e. g. Mount Pinatubo in 1991Pitari and Mancini (2002)Reduction in radiationEruption1-year laterProposal: put SO2 at about 25km in the equatorial region3. Increase the reflection by low-level cloud3. Increase the reflect

12、ion by low-level cloudAverage amount of low-level (stratocumulus) cloud3. Spray Turbine Concept3. Spray Turbine Concept Latham Salter (2006) 4.Increase the reflectivity (albedo) of the surfaceWhiten the dessertsEnhance reflectivity of human settlementsDevelop & use more reflective grassesManagem

13、ent of net Solar Radiation:Management of net Solar Radiation:Opportunities at 4 levels in the atmosphereOpportunities at 4 levels in the atmosphereComments: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

14、 time of yearSolar and thermal radiation act on the climate system in different waysIncreasing acidification of the ocean would continueFeasibility, cost, unintended impactsDiscussionDiscussionOur understanding of likely climate change due to increased greenhouse gases is limited. In general it is m

15、ore so for geo-engineering “solutions” .Need to be able to evaluate the actual impacts Ability to stop quickly is an important considerationSome private companies are already planning to start ocean fertilisation on a commercial basis, offering it as an off-setting mechanism Is it a “solution”? Is i

16、t possible to compensate for any increase in atmospheric greenhouse gases? Necessity for legal and political frameworkMight it take the pressure off the imperative to reduce greenhouse gas emissions?Is it a good way of buying time until serious greenhouse gas emission reductions have been agreed and

17、 executed?Stabilisation CO2 Concentrations and EmissionsCO2 concentration (ppm)CO2-equivalent concentration (ppm)Global mean temperature increase above pre-industrial level at equilibrium* (C)Peaking year for CO2 emissionsGlobal change in CO2 emissions in 2050 (% of 2000 emissions)350 400445 4902.0

18、2.42000 2015-50 to -85400 440490 5352.4 2.82000 2020-30 to -60440 485535 5902.8 3.22010 2030+5 to -30485 570590 7103.2 4.02020 2060+10 to +60570 660710 8554.0 4.92050 2080+25 to +85660 790855 1 1304.9 6.12060 2090+90 to +140* Based on the “best estimate” of climate sensitivity.Source: IPCC (2007). O

19、ECD/IEA 2007Stippled areas are where more than 90% of the models agree in the sign of the changePrecipitation increases very likely in high latitudesDecreases likely in most subtropical land regionsThis continues the observed patterns in recent trendsProjected patterns at end of 21Projected patterns

20、 at end of 21st st century: century: Change (%) in precipitation for one scenarioChange (%) in precipitation for one scenarioJune-AugIPCC 2007Dec-FebPossible CO2 Emissions for 450ppm StabilisationBy 2030, emissions are reduced to some 23 Gt, a reduction of 19 Gt compared with the Reference Scenario1015202530354045200520102015202020252030Gt of CO2CCS in industryCCS in power generationNuclear