Climate Change and Global Warming

Introduction

Climate change is one of the most significant global challenges because it affects ecosystems, agriculture, water availability, human health, infrastructure, economic development, and international security. Although climate has changed naturally throughout Earth’s history, the rapid warming observed since the nineteenth century is primarily attributable to human activities, especially greenhouse gas emissions from fossil fuel use, deforestation, and industrial processes.

Global warming refers specifically to the long-term increase in Earth’s average surface temperature. Climate change is broader: it includes changes in temperature, rainfall, atmospheric circulation, extreme weather patterns, oceans, ice, and other characteristics of the climate system.

Climate change is an international relations issue because greenhouse gases mix throughout the atmosphere, climate impacts cross borders, and countries differ in their historical emissions, current emissions, vulnerability, and capacity to respond. International cooperation is therefore essential to mitigation, adaptation, climate finance, technology transfer, and disaster-risk reduction.

Core Concepts

Climate: The long-term statistical characteristics of weather in a region or across the planet, including temperature, precipitation, humidity, winds, and seasonal patterns.

Weather: Atmospheric conditions at a particular place and time, including temperature, rainfall, wind, and cloud cover.

Climate change: A long-term change in the state of the climate, identifiable through changes in its average or variability over extended periods. It can result from natural processes and human activities.

Global warming: The long-term increase in Earth’s average surface temperature, particularly the warming associated with human-caused greenhouse gas emissions.

Anthropogenic climate change: Climate change caused by human activities, including fossil fuel combustion, land-use change, and certain industrial and agricultural processes.

Climate variability: Natural or other fluctuations in climate conditions around their longer-term average, occurring over different timescales.

Climate system: The interconnected components of the atmosphere, hydrosphere, cryosphere, lithosphere, and biosphere that influence Earth’s climate.

Climate baseline: A reference period used to compare temperature, rainfall, or other climate variables with observations from another period.

Pre-industrial period: A reference period before large-scale industrialization, frequently approximated using 1850–1900 in global warming assessments.

Climate anomaly: The difference between an observed climate value and the value expected under a specified reference period.

The Greenhouse Effect

The greenhouse effect is a natural process that keeps Earth warm enough to support life. Certain gases in the atmosphere absorb and re-emit infrared radiation, reducing the rate at which energy escapes directly into space.

Human activities increase the atmospheric concentration of several greenhouse gases, strengthening this natural effect and causing additional warming.

Greenhouse gases (GHGs): Atmospheric gases that absorb and emit infrared radiation, contributing to the greenhouse effect.

Carbon dioxide (CO₂): A major greenhouse gas released through fossil fuel combustion, cement production, deforestation, and other processes. It is also removed from the atmosphere through natural sinks such as vegetation and oceans.

Methane (CH₄): A potent greenhouse gas released by sources including fossil fuel production, livestock, rice cultivation, landfills, and wetlands.

Nitrous oxide (N₂O): A long-lived greenhouse gas associated with agricultural soils, fertilizer use, certain industrial processes, and combustion.

Fluorinated gases: A group of industrial gases, including hydrofluorocarbons and certain other compounds, some of which have very high warming effects per unit of mass.

Atmospheric concentration: The amount of a substance present in the atmosphere, commonly expressed in parts per million or parts per billion.

Radiative forcing: A measure of how a factor changes the balance between incoming and outgoing energy in the climate system. Positive forcing tends to warm the planet, while negative forcing tends to cool it.

Climate feedback: A process through which an initial climate change triggers effects that amplify or reduce that change.

Water-vapour feedback: Warming allows the atmosphere to hold more water vapour, which can strengthen the greenhouse effect and amplify initial warming.

Ice-albedo feedback: The process by which melting snow and ice expose darker surfaces that absorb more solar energy, contributing to further warming.

Sources of Greenhouse Gas Emissions

Fossil fuels: Coal, oil, and natural gas formed from ancient organic material. Their combustion releases carbon dioxide and contributes substantially to human-caused warming.

Deforestation: The removal of forests, which can release stored carbon and reduce the capacity of ecosystems to absorb carbon dioxide.

Land-use change: Changes in how land is used or managed, including forest conversion, agricultural expansion, and urban development, that can affect greenhouse gas emissions and carbon storage.

Industrial emissions: Greenhouse gases released through industrial processes, including cement production, chemical manufacturing, and certain metal-production activities.

Agricultural emissions: Emissions associated with livestock, fertilizers, rice cultivation, agricultural energy use, and land management.

Transport emissions: Greenhouse gas emissions from road vehicles, aviation, shipping, railways, and related transport activities.

Energy-sector emissions: Emissions arising from the production and use of energy, particularly from fossil fuel combustion.

Carbon sink: A natural or artificial system that absorbs more carbon than it releases over a specified period.

Carbon source: A process, activity, or system that releases more carbon into the atmosphere than it absorbs over a specified period.

Observed Changes and Climate Impacts

Rising global temperature: An increase in Earth’s average surface temperature relative to a reference period.

Heatwave: A period of unusually hot weather relative to the conditions normally experienced in a particular location and season.

Sea-level rise: An increase in the average level of the oceans, driven mainly by the thermal expansion of warming seawater and the addition of water from melting land ice.

Ocean acidification: A reduction in ocean pH caused primarily by the absorption of atmospheric carbon dioxide, which changes seawater chemistry and can affect marine organisms.

Ocean warming: The increase in ocean temperature as the oceans absorb much of the excess heat accumulating in the climate system.

Glacier retreat: The reduction in glacier size or extent when ice loss exceeds accumulation over time.

Cryosphere: The parts of Earth’s system where water exists in frozen form, including glaciers, ice sheets, sea ice, snow, and permafrost.

Permafrost thaw: The warming and thawing of ground that has remained frozen for at least two consecutive years. Thaw can damage infrastructure and release greenhouse gases from previously frozen organic matter.

Extreme precipitation: Rainfall or snowfall that is unusually intense relative to local climate conditions. Climate change can alter the likelihood and intensity of such events, although effects vary by region.

Drought: A prolonged period of unusually low water availability, often resulting from deficient precipitation and influenced by evaporation, soil moisture, water demand, and management.

Compound climate event: A situation in which multiple climate hazards occur together or in sequence, potentially creating greater damage than an individual hazard alone.

Tipping point: A threshold beyond which a component of the climate system may undergo substantial and potentially difficult-to-reverse change. The likelihood, timing, and consequences of particular tipping points vary.

Climate Risk and Vulnerability

Climate hazard: A climate-related event or trend that can cause harm, such as extreme heat, flooding, drought, or sea-level rise.

Exposure: The presence of people, infrastructure, livelihoods, ecosystems, or assets in locations that could be affected by climate hazards.

Vulnerability: The degree to which a system or population is susceptible to harm, shaped by factors such as poverty, health, infrastructure, institutions, and adaptive capacity.

Climate risk: The potential for adverse consequences arising from interactions among climate hazards, exposure, and vulnerability.

Climate resilience: The ability of people, institutions, infrastructure, or ecosystems to withstand climate impacts, adapt, and recover.

Climate-sensitive sector: A sector whose performance or risks are significantly influenced by climate conditions, such as agriculture, water, health, fisheries, or energy.

Climate-induced displacement: The movement of people in which climate-related impacts play a significant role, sometimes alongside conflict, poverty, or other factors.

Loss and damage: Harm caused by climate-related impacts, including both economic losses and non-economic harms. The term has a particular role in international climate negotiations.

Climate Change Mitigation

Climate change mitigation: Human intervention to reduce greenhouse gas emissions or enhance greenhouse gas removals.

Decarbonization: The reduction of carbon dioxide emissions associated with energy systems, industry, transport, and other economic activities.

Net-zero emissions: A condition in which human-caused greenhouse gas emissions are balanced by human-caused removals over a specified period, considering the gases and accounting rules included.

Carbon neutrality: A claim or target involving balancing carbon dioxide emissions with removals or eligible offsets under a specified accounting framework. It is not automatically equivalent to net-zero greenhouse gas emissions.

Carbon sequestration: The capture and storage of carbon in natural or engineered systems, such as forests, soils, geological formations, or certain industrial processes.

Carbon capture and storage (CCS): Technologies designed to capture carbon dioxide from industrial facilities or other sources and store it in suitable geological formations.

Renewable energy: Energy derived from sources that are naturally replenished, such as solar, wind, hydropower, and geothermal energy.

Energy efficiency: Achieving the same or a greater energy service with less energy input.

Carbon pricing: Policies that place an explicit or implicit cost on greenhouse gas emissions, including carbon taxes and emissions trading systems.

Carbon tax: A tax applied to carbon dioxide emissions or the carbon content of fuels, designed to influence production and consumption decisions.

Emissions trading system (ETS): A system in which regulated entities can trade emission allowances under an established cap or other rules.

Carbon offset: A claimed reduction or removal of emissions used to compensate for emissions occurring elsewhere. Its credibility depends on factors including additionality, measurement, permanence, and avoidance of double counting.

Climate Change Adaptation

Climate change adaptation: Adjustments in human or natural systems in response to actual or expected climate impacts, intended to reduce harm or take advantage of possible beneficial opportunities.

Adaptive capacity: The ability of a system, community, or institution to adjust to climate risks, reduce potential damage, and respond to changing conditions.

Climate-resilient infrastructure: Infrastructure designed, located, operated, or upgraded to withstand current and future climate hazards.

Nature-based solutions: Actions that protect, sustainably manage, or restore ecosystems to address societal challenges while supporting biodiversity and human well-being.

Ecosystem-based adaptation: The use of biodiversity and ecosystem services as part of a strategy to help people adapt to climate change.

Early warning system: A system that monitors hazards, assesses risks, communicates warnings, and supports timely protective action.

Disaster risk reduction (DRR): Policies and measures designed to prevent new disaster risks, reduce existing risks, and strengthen resilience.

Climate-smart agriculture: Approaches that seek to increase agricultural productivity, strengthen adaptation and resilience, and reduce emissions where feasible.

Managed retreat: The planned relocation of people or assets away from areas facing unacceptable risks, such as repeated flooding or coastal erosion.

Climate-proofing: Incorporating climate-risk assessments and appropriate protective measures into the planning and operation of projects or systems.

International Climate Governance

United Nations Framework Convention on Climate Change (UNFCCC): The international treaty adopted in 1992 that provides the foundation for global climate cooperation and negotiations.

Conference of the Parties (COP): The meeting of parties to a treaty, including the UNFCCC, where members review implementation and negotiate decisions within the treaty’s framework.

Kyoto Protocol: An agreement adopted in 1997 under the UNFCCC that established binding emission-reduction commitments for certain developed countries during specified commitment periods.

Paris Agreement: The 2015 climate agreement under the UNFCCC. It aims to hold the increase in global average temperature to well below 2°C above pre-industrial levels and pursue efforts to limit it to 1.5°C.

Nationally Determined Contribution (NDC): A climate action plan submitted by a party to the Paris Agreement, setting out its intended mitigation efforts and potentially adaptation and support-related information.

Global Stocktake: A process under the Paris Agreement for assessing collective progress toward its purpose and long-term goals, informing subsequent climate action.

Common but differentiated responsibilities and respective capabilities (CBDR-RC): A principle recognizing that all states have responsibilities to address global environmental challenges, while accounting for differences in historical contributions and capacities.

Climate finance: Financing intended to support climate mitigation, adaptation, and related activities.

Technology transfer: The sharing or movement of knowledge, technologies, expertise, and technical capabilities between countries or organizations.

Climate justice: An approach that considers fairness in the causes, consequences, responsibilities, and responses associated with climate change.

Key Distinctions

Key Terms at a Glance

• Global warming potential (GWP): A measure comparing the warming effect of a greenhouse gas over a specified period with that of carbon dioxide.
• Carbon dioxide equivalent (CO₂e): A common unit expressing the warming effect of different greenhouse gases using a specified conversion method.
• Greenhouse gas inventory: A systematic accounting of emissions and removals by sources and sinks.
• Climate attribution: The scientific assessment of the extent to which climate change influences a particular event or trend.
• Climate projection: A model-based estimate of possible future climate conditions under specified assumptions or scenarios.
• Climate scenario: A plausible description of future conditions used to assess possible climate outcomes.
• Climate finance gap: The difference between estimated climate-financing needs and available or mobilized finance.
• Carbon budget: The estimated total amount of carbon dioxide that can be emitted while retaining a specified probability of staying below a temperature threshold.
• Just transition: An approach that considers workers, communities, and social equity during the transition to a low-emission economy.
• Climate security: The study of how climate change interacts with conflict risks, livelihoods, displacement, resource pressures, and broader security conditions.

Related Glossaries

• 9.2 Human Security and Non-Traditional Security
• 12.5 Resources, Energy and Geoeconomics
• 12.6 Critical Minerals and Strategic Resources
• 17.4 Sustainable Development and SDGs
• 17.7 Food, Health and Human Security
• 18.2 Climate Security and Climate Diplomacy
• 18.3 Climate Finance and Climate Justice
• 18.4 Environmental Security and Resource Conflicts
• 18.5 Water Security and Transboundary Waters
• 18.6 Energy Transition and Renewable Energy
• 18.7 Biodiversity and Global Environmental Governance

Conclusion

Climate change involves far more than rising temperatures. It affects oceans, ecosystems, food systems, water resources, public health, infrastructure, and economic development. Mitigation addresses the causes by reducing emissions and enhancing removals, while adaptation reduces harm from actual or expected impacts. International climate governance provides a framework for collective action, but progress depends on national policies, financing, technology, scientific evidence, and cooperation among countries with different circumstances and capacities.