Maarg Manthan · Topic 20.12

Geo-Engineering for Climate Change and Sequestering CO2

Environment & Ecology › Protected Areas Lists and Recent Developments in Environment · Topic 20.12

Geo-engineering, also called climate engineering, means deliberate large-scale intervention in the Earth's climate system to counter climate change. It is divided into two broad groups. Carbon dioxide removal (CDR) takes CO2 out of the atmosphere and stores it, tackling the cause of warming, and includes afforestation, bioenergy with carbon capture and storage (BECCS), direct air capture, biochar, enhanced rock weathering, ocean alkalinity enhancement and ocean fertilisation. Solar radiation management (SRM) reflects a small part of incoming sunlight back to space to cool the planet, tackling the symptom, and includes stratospheric aerosol injection, marine cloud brightening, cirrus cloud thinning, space-based reflectors and brightening of surfaces. The natural example for stratospheric injection is the 1991 eruption of Mount Pinatubo, which cooled the Earth by about half a degree Celsius for a year or two. Sequestering CO2 means capturing it from power plants, industry or the air and storing it away from the atmosphere. Geological storage uses depleted oil and gas fields, deep saline aquifers and unmineable coal seams, mineral carbonation converts CO2 into stable carbonates, and biological storage uses forests, soils and oceans. SRM does not reduce CO2 or ocean acidification and carries risks such as disruption of monsoon rainfall, ozone loss, termination shock if stopped suddenly, and governance problems. The Convention on Biological Diversity adopted a de facto moratorium on climate-related geo-engineering in 2010, and the London Protocol was amended in 2013 to regulate marine geo-engineering, though the amendment is not yet in force. Hedge details: research and rules are evolving, so check the latest assessments.

5 min read · UPSC Prelims · Environment & Ecology · Protected Areas Lists and Recent Developments in Environment

At a Glance

Two groups CDR and SRM
CDR aim Remove CO2
SRM aim Reflect sunlight
Natural analogue Pinatubo 1991
Main risk Termination shock
Exam link UPSC Prelims, Environment & Ecology: Protected Areas Lists and Recent Developments in Environment

Where Does It Fit?

This topic follows carbon neutrality and examines deliberate technological interventions, which sit at the margin of climate policy and are discussed under both science and governance. Previous topic: Carbon Neutrality Concept and Negative Emissions. Next topic: Black Carbon and Its Climate Impact.

What Are the Two Types of Geo-Engineering?

Type	Details
Carbon dioxide removal (CDR)	Removes CO2 and stores it: forests, BECCS, direct air capture, biochar, enhanced weathering, ocean-based methods
Solar radiation management (SRM)	Reflects sunlight: stratospheric aerosols, marine cloud brightening, cirrus thinning, space mirrors, bright surfaces
CDR effect	Slow, addresses the cause, reduces ocean acidification if CO2 is removed
SRM effect	Fast cooling, does not remove CO2 or reduce ocean acidification
Cost	SRM is thought to be cheap to start but hard to govern; CDR can be costly
Risk	SRM: rainfall change, ozone loss, termination shock; CDR: land use, leakage, permanence
Governance	No single treaty; CBD moratorium of 2010 and London Protocol amendment of 2013

How Can CO2 Be Sequestered?

Geological storage: depleted oil and gas fields, deep saline aquifers and unmineable coal seams
Mineral carbonation: reacting CO2 with basalt or other rocks to form solid carbonates
Forests and soils: biological sequestration through growth and organic matter
Blue carbon: mangroves, seagrass and marshes
Ocean storage: deep ocean injection or alkalinity, with high uncertainty
Utilisation: CO2 used for chemicals, fuels and concrete curing
Monitoring: leak detection over decades
India: pilot projects and policy work on CCUS; potential in sedimentary basins and basalt in the Deccan

What Else Should You Remember?

IPCC view: CDR is needed at scale for 1.5 degree pathways, while SRM is not part of core scenarios and is poorly understood
Stratospheric aerosol injection: sulphate particles sprayed into the stratosphere to reflect light
Pinatubo: 1991 eruption in the Philippines; global cooling of around 0.5 degrees Celsius
Marine cloud brightening: spraying sea salt to make low clouds more reflective
Cirrus cloud thinning: reduces trapping of heat by thin ice clouds
Space mirrors: sunshades in space, a speculative idea
Albedo modification: white roofs and reflective surfaces; a local measure
Ocean fertilisation: adding iron to stimulate plankton; limited success and ecological concern
Enhanced weathering: crushed silicate rocks absorb CO2 over time
BECCS: plants absorb CO2; the biomass is burned for energy and the CO2 stored
DACCS: machines capture CO2 from air with high energy need
Biochar: charred biomass buried in soil
Termination shock: rapid warming if SRM stops suddenly while CO2 stays high
Monsoon risk: SRM could change rainfall patterns and hit South Asia
Ozone risk: sulphate particles may harm the ozone layer
Unequal effects: benefits and harms may differ by region
Moral hazard: belief in a technical fix may reduce emission cuts
CBD decision: Decision X/33 of 2010 urged caution and set a de facto moratorium
London Protocol: 2013 amendment on marine geo-engineering, not yet in force
Governance gap: no body decides on SRM tests or deployment
Research: outdoor SRM experiments have faced public and political opposition
Link to previous: see Carbon Neutrality Concept and Negative Emissions
Link to next: see Black Carbon and Its Climate Impact
Link to CCUS: see Carbon Neutrality Concept and Negative Emissions
Caution: the science and rules are evolving, so check the latest assessments
Exam hint: remember CDR versus SRM, Pinatubo, termination shock and the CBD decision
Royal Society view: Reports have said geo-engineering should be studied with caution and never replace mitigation
Ethics: Who decides the thermostat for the planet, and who is responsible for harm, are open questions
Developing countries: Regions that depend on the monsoon fear that SRM trials by a few states could disrupt rain
Testing: Small experiments are proposed to learn about aerosols, but several planned trials were halted after public concern
Cost of CDR: Direct air capture costs far more per tonne than forest-based removal today
Energy need: Direct air capture and enhanced weathering need large amounts of energy and mined material
Ocean acidification: Only CO2 removal and emission cuts address this; SRM does not

Why Does It Matter for the Exam?

Types: CDR and SRM
Example: Pinatubo 1991
Risk: Termination shock
Current affairs link: SRM debate
Common errors: saying SRM removes CO2

As an analytical point, CDR deals with the cause and is widely accepted as a supplement to cuts, while SRM only masks warming and creates new risks and governance questions. Neither can replace deep emission reductions.

Why Is This Topic Important?

CDR Cause
SRM Symptom
Risk Governance

What Came Next?

The next topic covers black carbon and its climate impact. Next topic: Black Carbon and Its Climate Impact.

Key People and Terms

CDR Carbon dioxide removal
SRM Solar radiation management
SAI Stratospheric aerosol injection
MCB Marine cloud brightening
Albedo Reflectivity
Termination shock Sudden rebound of warming

Exam Corner

Points to Remember

Two types: CDR and SRM.
Natural example: Pinatubo 1991.
SRM risk: termination shock.
CBD decision 2010.
London Protocol amendment 2013.

Do Not Confuse With

CDR and SRM Remove carbon versus reflect sunlight
Sequestration and storage Capturing versus keeping away
Geo-engineering and mitigation Technical intervention versus emission cuts

Memory Hook

CDR cleans the cause, SRM shades the sun; stop it fast and the heat will run.

Mains Angle

Questions ask for types, examples and risks. These points help.

Types CDR, SRM
Risks Governance
Role Supplement

A Question You May Face

An original practice question, not a past paper question.

“What is geo-engineering? Discuss its types, risks and governance challenges.”

How to Answer

Types Two.
Examples Methods.
Risks Shock.
Governance Gap.

GS Relevance

Prelims: types of geo-engineering, examples, treaties. GS Paper 3: climate technology and governance.

Frequently Asked Questions

What is geo-engineering?

Geo-engineering is deliberate large-scale intervention in the climate system to counter global warming. It has two broad groups: carbon dioxide removal, which takes CO2 out of the air, and solar radiation management, which reflects some sunlight to cool the planet. Both are debated for their cost, effectiveness, risks and governance.

What is solar radiation management?

Solar radiation management means reflecting a small part of sunlight back to space to reduce warming, for example by injecting reflective particles into the stratosphere, brightening marine clouds or thinning cirrus clouds. It acts quickly but does not reduce CO2 or ocean acidification, and has risks such as rainfall changes and termination shock.

What is termination shock?

Termination shock is the rapid rise in temperature that could occur if solar radiation management were started and later stopped suddenly while greenhouse gas levels remained high. The sunlight-reflecting effect would end quickly, and warming that had been hidden would come back faster than ecosystems and people can adapt.

How can carbon dioxide be sequestered?

Carbon dioxide can be captured from power plants, industry or the air and stored in depleted oil and gas fields, deep saline aquifers or unmineable coal seams, converted into stable carbonates through mineral carbonation, or held in forests, soils and coastal ecosystems. Monitoring is needed to ensure long-term storage.

Is geo-engineering regulated internationally?

There is no single treaty. The Convention on Biological Diversity adopted a decision in 2010 urging caution and a de facto moratorium on climate-related geo-engineering. The London Protocol was amended in 2013 to regulate marine geo-engineering, but that amendment is not yet in force, so governance remains incomplete.

PYQ Practice — Statement Analysis

1 Solar radiation management removes CO2 from the air.

False

It reflects sunlight.

2 Pinatubo's eruption cooled the Earth temporarily.

True

By about 0.5 degrees Celsius.

3 BECCS is a form of carbon dioxide removal.