Introduction: Why Greenhouse Gas Emissions Have Become a Central Maritime Issue
Climate change is one of the defining global challenges of this century. International shipping, while the most energy-efficient mode of mass transport, contributes a measurable share of global greenhouse gas (GHG) emissions, primarily through the combustion of fossil fuels. As global trade continues to grow, reducing emissions from ships has become a strategic priority for governments, industry, and international organisations.
Unlike many land-based sectors, shipping operates across borders and oceans, making international regulation essential. The International Maritime Organization (IMO) is the body responsible for addressing GHG emissions from international shipping. Over the last decade, the IMO has developed a data-driven regulatory framework to understand emissions, improve efficiency, and guide the sector toward decarbonisation.
To support transparency, analysis, and policy development, information related to ship GHG emissions is made available through the “Greenhouse Gas (GHG) Emissions from Ships” module of the Global Integrated Shipping Information System (GISIS).
This article provides a comprehensive introduction and practical guide to the GHG Emissions option in GISIS. It explains the regulatory background, the role of data collection, how GISIS supports IMO climate policy, and why this module is essential for administrations, shipowners, researchers, educators, and maritime professionals worldwide.
Understanding GISIS and Its Role in Climate Governance
What Is the IMO Global Integrated Shipping Information System?
The IMO GISIS (Global Integrated Shipping Information System) is an online platform managed by the International Maritime Organization that provides transparent and reliable data on ships, companies, flag States, and maritime compliance. It brings together information on safety, security, pollution prevention, port State control, and casualty reports in one place. For seafarers, maritime professionals, researchers, and regulators, IMO GISIS is a trusted tool to check vessel records, track compliance with IMO conventions, and understand global shipping performance. Its free public access supports safer seas, better regulation, and informed decision-making across the maritime industry.
The GHG Emissions module is a cornerstone of IMO’s climate strategy, linking technical data with regulatory decision-making.
Why the IMO Focuses on GHG Emissions from Ships
Shipping and Climate Change
Ships mainly emit:
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Carbon dioxide (CO₂)
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Methane (CH₄), particularly from some alternative fuels
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Nitrous oxide (N₂O)
CO₂ accounts for the vast majority of shipping’s GHG emissions and is directly linked to fuel consumption.
The Need for Global Regulation
Because ships operate internationally:
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National regulations alone are ineffective
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Fragmented rules would distort competition
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A global, uniform approach is required
The IMO provides this global framework.
IMO’s Initial GHG Strategy and Data-Driven Approach
Why Data Comes First
Before introducing mandatory emission limits, the IMO recognized the need to:
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Understand real emissions from ships
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Identify trends across ship types and sizes
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Assess the impact of potential measures
This led to the development of global data collection systems, supported by GISIS.
Legal Framework for GHG Emissions Data
MARPOL Annex VI
GHG regulation is implemented through MARPOL Annex VI, which already addresses air pollution from ships. Under Annex VI, the IMO introduced:
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Mandatory fuel oil consumption data collection
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Energy efficiency requirements
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Carbon intensity measures
The GHG Emissions module in GISIS builds on this framework.
Relationship with the IMO Data Collection System (DCS)
IMO DCS as the Foundation
The IMO Data Collection System (DCS) requires ships of 5,000 gross tonnage and above engaged in international voyages to report annually:
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Fuel oil consumption
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Distance travelled
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Hours underway
This data is verified by flag States and transmitted to the IMO.
From Fuel Data to GHG Emissions
Using standard emission factors, fuel consumption data is converted into:
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CO₂ emissions estimates
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Emissions intensity indicators
GISIS provides a platform for handling and analysing this information at aggregated level.
Purpose of the GHG Emissions Module in GISIS
Core Objectives
The GHG Emissions module aims to:
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Support monitoring of shipping’s GHG emissions
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Provide transparency on aggregated emissions data
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Assist IMO in evaluating regulatory measures
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Enable evidence-based climate policymaking
It is a policy and governance tool, not a real-time emission tracking system.
What Information Is Available in the GISIS GHG Module?
Types of Information Provided
Depending on IMO releases and Member State submissions, the module may include:
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Aggregated GHG emissions data
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Emissions trends by ship type or size category
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Analytical outputs supporting IMO studies
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References to climate-related IMO measures
Individual ship-level emission data is not publicly disclosed.
Who Submits and Manages GHG Emissions Data?
Role of Shipowners and Operators
Shipowners are responsible for:
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Monitoring fuel consumption onboard
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Collecting accurate operational data
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Submitting annual reports to flag States
Role of Flag States
Flag States:
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Verify submitted data
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Issue Statements of Compliance
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Forward aggregated data to the IMO
Role of the IMO
The IMO:
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Aggregates data from all Member States
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Ensures confidentiality and data quality
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Uses the data for impact assessment and policymaking
GISIS is the digital interface supporting this process.
Link with Energy Efficiency Measures
EEDI and EEXI
The GHG emissions framework is closely linked to:
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Energy Efficiency Design Index (EEDI) for new ships
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Energy Efficiency Existing Ship Index (EEXI) for existing ships
These measures address technical efficiency, while GHG data reflects operational reality.
Carbon Intensity Indicator (CII)
The Carbon Intensity Indicator (CII) uses:
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Fuel consumption
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Distance travelled
to rate ships annually. GISIS GHG data supports understanding of fleet-level CII performance.
Importance of GHG Emissions Data for Policymaking
Evaluating Regulatory Effectiveness
Without data, the IMO cannot:
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Assess whether measures reduce emissions
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Identify unintended consequences
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Adjust regulations over time
GISIS enables monitor-review-adjust policymaking.
Supporting IMO Climate Negotiations
Aggregated emissions data supports:
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IMO committee discussions
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Negotiations between Member States
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Development of mid-term and long-term measures
Practical Use Cases of the GHG Emissions Module
IMO and Member States
Administrations use the data to:
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Develop national positions at IMO
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Assess fleet performance
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Support climate reporting
Researchers and Academia
Researchers use GISIS-based data to:
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Model emission scenarios
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Study efficiency trends
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Support peer-reviewed research
Industry and Technology Developers
Industry stakeholders benefit indirectly from:
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Better understanding of emission drivers
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Evidence supporting investment decisions
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Clear regulatory signals
Relationship with Other GISIS Modules
The GHG Emissions module complements:
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Ship Fuel Oil Consumption – primary data source
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Fuel Oil Quality – sulphur and compliance context
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Pollution Prevention Equipment – emission control technologies
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Survey and Certification – regulatory enforcement
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Status of Treaties – legal applicability
Together, these modules form a complete climate governance ecosystem.
Common Misunderstandings About GHG Data in GISIS
GISIS Is Not a Public Emissions Ranking Tool
The system does not:
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Rank individual ships or companies
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Publish commercially sensitive data
Its purpose is policy development, not public comparison.
GHG Data Is Historical, Not Real-Time
Reported data:
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Is annual
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Reflects past performance
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Is used for trend analysis
Best Practices for Using the GHG Emissions Module
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Use it for trend and policy analysis, not operational control
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Combine it with academic and IMO reports
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Understand its link with MARPOL Annex VI measures
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Integrate insights into maritime climate education
Educational Value for Maritime Training and Academia
For maritime education, this module provides:
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Clear understanding of shipping’s climate impact
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Insight into data-driven regulation
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Real-world context for decarbonisation strategies
It is especially useful in courses on:
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Maritime environmental policy
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Energy management
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Marine engineering
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Maritime law and governance
GHG Emissions Data and the Future of Shipping
Supporting the IMO 2050 Ambition
GHG data underpins:
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Long-term emission reduction pathways
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Market-based measures
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Transition to alternative fuels
Increasing Importance of Digital Transparency
As reporting systems evolve:
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Data accuracy will improve
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Integration with other digital platforms will increase
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GISIS will remain a central reference point
Conclusion: Measuring Emissions to Enable Maritime Decarbonisation
The Greenhouse Gas (GHG) Emissions from Ships option in the IMO Global Integrated Shipping Information System is a foundational element of global maritime climate governance.
By providing structured, aggregated information derived from mandatory fuel consumption reporting, the module enables the IMO and its Member States to understand emissions, evaluate measures, and design effective policies.
For administrations, shipowners, researchers, educators, and students, the GISIS GHG module offers a trusted and authoritative window into how international shipping is addressing climate change. In a sector facing profound transformation, accurate data is not just supportive—it is essential.