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

Causes of the current imbalance in the energy budget

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

Projections of globally averaged surface warming

IPCC 2007

Different scenarios

IPCC (2007) Surface Temperature Projections 2020s & 2090s relative

to 1980-99

2020s 2090s

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: 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

Oceanic carbon cycle

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

Kiehl and Trenberth 1997

The Earth’s energy budget

1

2

34

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

uct

ion

in r

adia

tio

n

Eru

ptio

n

1-ye

ar la

ter

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 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

Stratospheric Circulation and Ozone distribution

Proposal: put SO2 at about 25km in the equatorial region