Post on 17-Dec-2015
transcript
To what extent is geo-engineering the solution to the climate change problem?
Brian HoskinsDirector, Grantham Institute for Climate Change
Imperial College& Professor of Meteorology, University of Reading
“Greenhouse” gases determine height of layer from which heat escapes
More greenhouse gases:
higher level
colder temperature
less heat lost
global warming
(water vapour) carbon dioxide, methane,…
Temperature and greenhouse gases in past 650,000 y
proxy for temp
methane
carbon dioxide
nitrous oxide
todaytime
IPCC 2007
Since 1970, rise in: Decrease in: Global surface temperatures NH Snow extent Tropospheric temperatures Arctic sea ice Global ocean temperatures Glaciers Global sea level Cold temperatures Water vapour Rainfall intensity Precipitation in extratropics Hurricane intensity Drought Extreme high temperatures Heat waves
Intergovernmental Panel on Climate Change Fourth Assessment Report (2007): “Global Warming is unequivocal”
Estimates of NH temperatures in the past 1000 years
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: geo-
engineering
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
SeaWiFS Project, NASA/Goddard Space Flight Center, and ORBIMAGE.
Biological activity in the ocean
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
1. In Space: Solar Interceptor
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)At a point where gravitational and
centrifugal forces are in equilibrium (Lagrange point)
2. In the stratosphere, mimicking a volcanic eruption
e. g. Mount Pinatubo in 1991
Pitari and Mancini (2002)
Red
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in r
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Proposal: put SO2 at about 25km in the equatorial region
4.Increase the reflectivity (albedo) of the surface
1. Whiten the desserts
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
Top ofAtmosphere
Surface
AerosolScattering
Cloud Albedo
Solar Interceptor
Grassland, 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
concentration (ppm)
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
* Based on the “best estimate” of climate sensitivity.Source: IPCC (2007).
© OECD/IEA 2007
Stippled areas are where more than 90% of the models agree in the sign of the change
Precipitation increases very likely in high latitudes
Decreases likely in most subtropical land regions
This continues the observed patterns in recent trends
Projected patterns at end of 21st century: Change (%) in
precipitation for one scenarioJune-Aug
IPCC 2007
Dec-Feb
Possible CO2 Emissions for 450ppm Stabilisation
By 2030, emissions are reduced to some 23 Gt, a reduction of 19 Gt compared with the Reference
Scenario
10
15
20
25
30
35
40
45
2005 2010 2015 2020 2025 2030
Gt o
f CO 2
CCS in industryCCS in power generationNuclearRenewablesSwitching from coal to gasEnd Use electricity efficiency
End Use fuel efficiency
Reference Scenario
450 Stabilisation Case27 Gt
42 Gt
23 Gt
Energy-Related CO2 Emissions
© OECD/IEA 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: geo-
engineering