Post on 14-Jan-2016
description
Earth System Engineering - A Way Out of Trouble or a Cure
Worse than Disease?
K. KasturiranganMember
Planning CommissionGovernment of India
New Delhi
Foundation Day Lecture Ministry of Earth Sciences
Government of IndiaNew Delhi
July 27, 2009
Earth System Engineering – A Way Out of Trouble or a Cure
Worse Than Disease?• Describes proposals to deliberately manipulate the earth’s climate to
counter-act the effects of global warming from Green House Gas emissions.
• These are not suggested as alternative to emissions control but rather an accompanying strategy.
• Current surge of interest in this area arises from the fact that global warming could be both real and dangerous.
• Notably a complex discipline requiring collation of knowledge in
Scientific disciplines including Atmospheric Chemistry, Ecology, Meteorology and Plant Biology.
Engineering disciplines including Aeronautical Engineering, Naval Architecture & Ballistics.
Management and control disciplines such as risk management and operational research.
Source: IPCC AR4 Ch.6
The rate of increase of population in the last 2000 years (right) is very similar to the rate of increase in the radiative forcing due to greenhouse gases (inset).
Systems Approach: Interactions among components, feedbacks, affecting the total system
Source: IPCC AR4
Inference:The effect of external forcings cannot be ignored; these are unpredictable and may hinder geoengineeringefforts
Comparison between temperature rise as derived from models and observations since the year 1860
Systems Approach
• Interactions and feedbacks among components and these affect the whole system
• Known feedbacks: ice-albedo(+), vegetation (-), cloud-solar radiation(-); cloud-terrestrial radiation (+); Water vapour(+); CO2 -weathering (-); aerosol-clouds-precipitation
• Both external and internal forcings must be taken into account
• Non-linear responses/Thresholds have to be identified and quantified
Inadequacy of models• Models solve partial differential equations that are sensitive to
the initial conditions; small differences in initial conditions may lead to widely different solutions.
• Models do not parameterize all the feedbacks in the Earth System. Models have low spatial resolution.
• Most feedbacks require accurate quantification before they can be incorporated in the models.
• The more sophisticated the model, the more is the requirement for field data (specifically over tropics).
• Illustration with Paleocene Eocene Thermal Maximum (PETM).
1. Palaeoanalogue of Global change?
2. Models unable to predict the warming in high latitudes: clouds that form in high CO2 atmosphere could be different?
3. PETM: ΔT =10 to 30ka atmospheric warming of 5 to 6°C
Source: IPCC AR4 Ch.6
Geoengineering ideas proposed
Carbon Sequestration
(i) Afforestation (ii) Direct CO2 capture
(iii) Petrification of CO2 (iv) Ocean fertilization
Changing the Earth’s effective Albedo(i) Space mirrors (ii) Stratospheric sulphur aerolsols (iii) stratospheric balloons with alumina aerosols (iv) Low stratospheric dust/soot (iv) stimulation of white clouds (v) cool roofs
Removal of atmospheric CFCs
The advantages of global warming include intensifictaion of the hydrological Cycle by water vapour feedback: increased monsoon is expected, and fertilization of plants.
Attennuation of insolation might adversely impact these benefits, e.g. Monsoons, a concern for Asian countries; on the other hand, they might benefit by reduction in extreme weather events
SSTs have increased in the recent years (blue) and so have the destructive power of cyclones (green).
Partition of Anthropogenic Carbon Emissions into Sinks
Canadell et al. 2007, PNAS
Ocean removes ~ 24% Land removes ~ 30%55% were removed by natural sinks
45% of all CO2 emissions accumulated in the atmosphere
The Airborne FractionThe fraction of the annual anthropogenic emissions that remains in the atmosphere
AtmosphereAtmosphere
[2000-2006]
13
• Plankton grow, mature and die—taking carbon with them to the deep ocean
• They have a larger effect on climate than any single other process or group of organisms.
• Of the ~750 billion tons of CO2 that turn over annually, plankton process 45%
• 99% of marine life relies on plankton—they form the base of the marine food chain.
THE BIOLOGICAL PUMP
45% of annual carbon flux is processed by phytoplankton
• “The efficiency of natural sinks has decreased by 10% over the last 50 years (and will continue to do so in the future), implying that the longer we wait to reduce emissions, the larger the cuts needed to stabilize atmospheric CO2.”
• “All of these changes characterize a carbon cycle that is generating stronger climate forcing and sooner than expected.”
Conclusions about the ocean sink from the Global Carbon Project:
Canadell et al. 2007, PNAS
• Part of the decline is attributed to up to a 30% decrease in the efficiency of the Southern Ocean sink over the last 20 years.
• This sink removes annually 0.7 Pg of anthropogenic carbon.
• The decline is attributed to the strengthening of the winds around Antarctica which enhances ventilation of natural carbon-rich deep waters.
• The strengthening of the winds is attributed to global warming and the ozone hole.
Causes of the decrease in efficiency of the ocean sink
Le Quéré et al. 2007, Science
Cred
it: N
.Met
zl, A
ugus
t 200
0, o
cean
ogra
phic
crui
se O
ISO
-5
Iron experiments in world Ocean from 1993-2005
An oceanic phytoplankton bloom
in the South Atlantic Ocean, off
the coast of Argentina.
Encouraging such blooms with
iron fertilization could lock up
carbon on the seabed
Source: Moderate Resolution Imaging
Spectroradiometer (MODIS) on NASA’s Aqua
satellite
Comparison of iron fertilization experiments
0
50
100
150
200
250
300
IronEx II SEEDS SERIES SOIREE EisenEx SOFEXNorth
SOFEXSouth
EIFEX
MLD
(m
) / C
hl a
(mg m
-2)
0
5
10
15
20
25
Chl a
(mg m
-3)
MLD (m)Chl a (mg m-2)Chl a (mg m-3)
17*
13
18
21
13
38
37
20
* = duration of experiment in days
How much CO2 can the biological pump sequester in the Southern Ocean?
If ALL the nitrate in the mixed layer (~150m) were converted into phytoplankton biomass,
and if all this biomass sank out of the mixed layer
and if all the resultant CO2 deficit were compensated by uptake from the atmosphere
then
The maximum amount of CO2 that could be sequestered would amount to about 1 (one) Gigatonne of CO2
Equivalent to ~15 % of annual input by humans
This maximum amount could be removed about once every 4 years.
Source:Victor Smetacek
Ocean acidification affects the growth of calcifying organisms: Calcification and shell growth rates – coccolithophoridae. The efficiency
of the oceans for uptake of CO2 is thus reduced significantly.
Courtesy: Zondervan et al 2001
Change in sea surface pH caused by anthropogenic CO2 between the 1700s and
the 1990s. This ocean acidification will still be a major problem unless atmospheric
CO2 is reduced.
Source: Global Ocean Data Analysis Project & World Ocean Atlas Climatologies
Courtesy: Rost and Riebesell 2004, (Springer)
Varying Photosynthetic response of biota in the sea
Some of these may be more effective in removing CO2 from the atmosphere. The relative geographical distribution of various species and the overall efficiency for
CO2 removal is yet to be quantified.
Conclusions• Viable options:
(i) Use alternative energy sources, fuel-efficient
engines to control emissions, prevent direct
emissions (ii) afforestation (land) and
fertilization (ocean) to scavenge CO2 from the
atmosphere (iii) Peterification of CO2 by
reaction with peridotite.
• Coordinated research to precisely quantify
various feedbacks (e.g. soil carbon residence
times, extreme weather events)