10.4 Future scenarios of greenhouse gas emissions
3 min read•july 22, 2024
Greenhouse gas emissions shape our climate future. Population growth, economic development, and technology influence emission scenarios. These factors determine CO2 concentrations, impacting global temperatures, sea levels, and weather patterns.
and mitigation strategies play a crucial role in curbing emissions. , , and sustainable practices can help limit warming. The choices we make today will determine the severity of future climate impacts.
Factors Influencing Future Greenhouse Gas Emissions and Their Impacts
Factors in emission scenarios
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- Population growth increases energy demand and consumption as more people require resources
- Economic development affects emissions as rising global GDP and per capita income drive energy demand while shifting from agriculture to industry and services can change emission patterns
- Technological advancements improve efficiency in energy production and consumption and enable development of low-carbon and renewable energy technologies (solar, wind)
- Energy mix and consumption patterns determine the proportion of fossil fuels (coal, oil, natural gas), nuclear, and renewable energy sources and are influenced by changes in energy consumption behavior and lifestyle choices
- Land use changes release stored carbon through deforestation and land conversion (agriculture) while afforestation and reforestation can act as carbon sinks by absorbing CO2
- Climate policies and international agreements shape emissions through carbon taxes, cap-and-trade systems, regulations, and adherence to global and commitments ()
Comparison of projected concentrations
- Representative Concentration Pathways (RCPs) describe different emission scenarios:
- RCP2.6: Stringent mitigation scenario where CO2 concentration peaks and declines
- and RCP6.0: Intermediate scenarios with stabilization of CO2 concentrations
- : High emission scenario where CO2 concentration continues to rise
- Special Report on Emission Scenarios () outlines alternative futures:
- assumes rapid economic growth, population peak mid-century, and new technologies (clean energy)
- describes a heterogeneous world with high population growth and slow technological change
- envisions a convergent world with population peak mid-century and shift to clean technologies (renewables)
- projects intermediate population and economic growth with local sustainability solutions (green infrastructure)
- Shared Socioeconomic Pathways (SSPs) consider socioeconomic challenges:
- : Sustainability-focused with low challenges for mitigation and adaptation
- : Middle of the road with moderate challenges for mitigation and adaptation
- : Regional rivalry leading to high challenges for mitigation and adaptation
- : Inequality results in low challenges for mitigation but high for adaptation
- : Fossil-fueled development creates high challenges for mitigation but low for adaptation
Climate Impacts and Mitigation Strategies
Impacts of scenarios on climate
- increases more under higher emission scenarios while the Paris Agreement aims to limit warming to well below 2℃ above pre-industrial levels
- occurs due to thermal expansion of oceans and melting of land-based ice (glaciers, ice sheets) with higher emission scenarios resulting in more significant sea level rise
- Changes in precipitation patterns intensify the water cycle leading to more frequent and intense droughts and floods with regional variations depending on the emission scenario
- Extreme weather events like heatwaves and hurricanes increase in frequency and intensity with higher emission scenarios amplifying the associated risks
- Ecosystem impacts include shifts in species distribution (migration), phenology (timing of events), and ecosystem composition (biodiversity) with higher emission scenarios posing greater risks to biodiversity and ecosystem services (pollination, water filtration)
Role of policies and technologies
- Carbon pricing mechanisms like carbon taxes and emissions trading systems incentivize emission reductions by making polluting activities more expensive and encouraging adoption of low-carbon technologies and practices
- Renewable energy deployment increases the share of renewable energy sources (solar, wind, hydro) in the global energy mix supported by technological advancements and cost reductions
- Energy efficiency measures reduce energy consumption and associated greenhouse gas emissions by improving the efficiency of buildings (insulation), transportation (electric vehicles), and industrial processes (cogeneration)
- (CCS) technologies mitigate emissions from fossil fuel-based energy production by capturing and storing CO2 emissions from point sources (power plants, factories)
- Sustainable land management practices reduce emissions from agriculture and land use changes through afforestation, reforestation, and sustainable agricultural practices (no-till farming, precision agriculture)
- International cooperation and agreements facilitate global efforts to set and achieve emission reduction targets through collaboration on technology transfer, capacity building, and climate finance (Green Climate Fund)
Key Terms to Review (24)
A1 Family: The A1 family refers to a group of future greenhouse gas emission scenarios characterized by high economic growth, rapid technological advancement, and a focus on globalization. This scenario outlines a world where the demand for energy rises significantly due to increased industrial activity and consumption patterns, leading to a significant rise in greenhouse gas emissions, especially carbon dioxide. It serves as a critical benchmark for understanding potential climate impacts and policy implications related to global warming.
A2 family: The a2 family refers to a group of greenhouse gas emission scenarios characterized by high levels of emissions driven by economic growth and increased energy use without significant policy intervention. These scenarios project a future where global population continues to grow, technological advancements occur, and the reliance on fossil fuels remains prevalent, leading to higher concentrations of greenhouse gases in the atmosphere.
B1 family: The b1 family refers to a specific group of greenhouse gases (GHGs) categorized in climate modeling scenarios that represent projected future emissions based on certain socio-economic pathways. This family includes gases like carbon dioxide (CO₂), methane (CH₄), and nitrous oxide (N₂O) that are essential for understanding how human activities influence climate change. The term is crucial in the context of evaluating potential future scenarios of emissions, which help in devising strategies for mitigation and adaptation.
B2 family: The b2 family refers to a specific grouping of scenarios within climate models that predict future greenhouse gas emissions based on various socio-economic factors and technological advancements. This family is characterized by its focus on development that leads to low emissions, emphasizing sustainability and environmental considerations while also addressing social equity and economic growth. These scenarios help in understanding how different choices made today can impact the trajectory of future emissions and climate outcomes.
Carbon capture and storage: Carbon capture and storage (CCS) is a technological process that captures carbon dioxide emissions produced from the use of fossil fuels in electricity generation and industrial processes, preventing the gas from entering the atmosphere. This technology is critical for reducing greenhouse gas emissions and mitigating climate change, especially when looking at future scenarios that involve ongoing fossil fuel use. CCS connects directly to the types and sources of greenhouse gases emitted, addresses human activities that disrupt the carbon cycle, and plays a significant role in advancing innovative technologies aimed at managing carbon emissions.
Carbon pricing: Carbon pricing is a method for reducing global warming emissions by assigning a cost to carbon emissions, encouraging polluters to reduce their carbon footprint. This economic tool aims to internalize the environmental costs of greenhouse gas emissions, making it more expensive to emit carbon and incentivizing cleaner alternatives. By incorporating the cost of emissions into market mechanisms, carbon pricing connects directly with climate policies, financial strategies, and future scenarios for global greenhouse gas emissions.
Climate feedbacks: Climate feedbacks are processes that can amplify or dampen the effects of climate change, influencing the Earth's temperature and climate system. These feedbacks can either be positive, which enhance warming, or negative, which counteract it, and they play a crucial role in shaping future climate scenarios, temperature trends, historical events, atmosphere-ocean interactions, and greenhouse gas dynamics.
Climate policies: Climate policies refer to strategies and regulations implemented by governments and organizations aimed at mitigating climate change and its impacts. These policies are designed to reduce greenhouse gas emissions, promote renewable energy sources, enhance energy efficiency, and protect natural resources. By addressing both the causes and effects of climate change, climate policies play a crucial role in shaping future scenarios of greenhouse gas emissions and guiding society towards a more sustainable path.
Climate resilience: Climate resilience refers to the ability of systems, communities, and ecosystems to anticipate, prepare for, respond to, and recover from climate-related impacts while maintaining essential functions. This concept emphasizes not only bouncing back from disturbances but also adapting and transforming to mitigate future risks and uncertainties related to climate change.
Emission Pathways: Emission pathways refer to the various scenarios that describe how greenhouse gas emissions could evolve over time, depending on factors such as technological advancements, policy decisions, and societal behaviors. These pathways help project potential future climate outcomes and are essential for understanding the implications of different levels of emissions on global warming and climate change.
Emission reduction targets: Emission reduction targets are specific goals set by governments or organizations to decrease the amount of greenhouse gases released into the atmosphere over a defined period. These targets are crucial for addressing climate change, as they guide policies and initiatives aimed at reducing overall emissions and help in measuring progress towards sustainability. They play a significant role in future projections of greenhouse gas emissions and are often influenced by international agreements that outline collective responsibilities.
Global mean surface temperature: Global mean surface temperature refers to the average temperature of the Earth's surface, calculated from both land and ocean temperatures. This metric is essential for understanding climate change, as it reflects the overall warming or cooling of the planet due to factors like greenhouse gas emissions and natural climate variability. Changes in this temperature can indicate shifts in climate patterns and influence weather events across the globe.
Paris Agreement: The Paris Agreement is a landmark international treaty adopted in 2015 that aims to address climate change by limiting global warming to well below 2 degrees Celsius above pre-industrial levels, while pursuing efforts to limit the temperature increase to 1.5 degrees Celsius. It establishes a framework for countries to set and achieve their own greenhouse gas reduction targets, emphasizing the importance of sustainable development and climate resilience.
Rcp4.5: RCP4.5, or Representative Concentration Pathway 4.5, is a greenhouse gas concentration trajectory that aims for a stabilization of radiative forcing at 4.5 watts per square meter by the year 2100. This pathway reflects a scenario where global emissions peak around 2040 and then decline, leading to a moderate level of climate change. RCP4.5 is often used in climate modeling to assess future climate impacts and to guide policy decisions on mitigation strategies.
Rcp8.5: RCP8.5, or Representative Concentration Pathway 8.5, is a high greenhouse gas emissions scenario that projects a significant increase in global temperatures and radiative forcing by the end of the century. It is often used in climate models to simulate a future with minimal efforts to curb emissions, resulting in severe climate impacts such as extreme weather, sea level rise, and biodiversity loss.
Renewable energy: Renewable energy refers to energy derived from natural resources that are replenished at a faster rate than they are consumed. This includes sources such as solar, wind, hydroelectric, and geothermal energy, which play a crucial role in reducing greenhouse gas emissions and mitigating climate change impacts. By replacing fossil fuels with renewable energy, we can achieve significant reductions in radiative forcing and global warming potential while supporting sustainable future climate scenarios.
Sea Level Rise: Sea level rise refers to the increase in the average level of the world's oceans due to the melting of ice sheets and glaciers, as well as the thermal expansion of seawater as it warms. This phenomenon is closely linked to climate change and global warming, which drive the changes in temperature and ice mass that contribute to rising sea levels, impacting coastal regions and ecosystems.
SRES: SRES stands for Special Report on Emissions Scenarios, a key framework developed by the Intergovernmental Panel on Climate Change (IPCC) that outlines different potential future scenarios of greenhouse gas emissions. These scenarios are based on varying assumptions about demographic, economic, technological, and environmental changes that could occur in the future, allowing researchers to model how these changes might impact climate systems and global temperatures. The SRES is essential for understanding the range of possible climate futures and informs policy decisions regarding climate change mitigation and adaptation strategies.
Ssp1: SSP1, or Shared Socioeconomic Pathway 1, is a scenario framework that envisions a sustainable and inclusive world by the year 2100, characterized by low greenhouse gas emissions and significant investments in environmental protection. This pathway highlights the importance of global cooperation, technological advancement, and a strong focus on sustainable development to achieve climate goals while fostering social equity and economic growth.
Ssp2: SSP2, or Shared Socioeconomic Pathway 2, represents a scenario that outlines a future of moderate challenges to climate adaptation and mitigation. It assumes a world where economic growth is moderate, population growth is stable, and there are significant efforts made toward sustainable development. This scenario emphasizes a balance between economic progress and environmental sustainability, highlighting the societal choices that influence greenhouse gas emissions and climate impacts.
Ssp3: SSP3, or Shared Socioeconomic Pathway 3, is one of the scenarios used to project future greenhouse gas emissions and their impacts on climate change. This pathway outlines a world that is characterized by regional rivalry and a fragmented global economy, leading to slower economic growth, higher inequalities, and challenges in achieving sustainability goals. As a result, SSP3 reflects a future with limited cooperation between nations, which significantly influences emission trajectories and climate policies.
Ssp4: SSP4, or Shared Socioeconomic Pathway 4, is a scenario that depicts a world characterized by a fragmented society and regional disparities. It highlights challenges in governance and inequality, with regions experiencing varying levels of development and adaptation to climate change. This scenario is crucial for understanding future greenhouse gas emissions trajectories, as it reflects socio-economic dynamics and policy responses that could influence climate change outcomes.
Ssp5: SSP5, or Shared Socioeconomic Pathway 5, refers to a specific scenario within climate modeling that envisions a world driven by fossil-fuel-based energy, high economic growth, and rapid technological advancements. This pathway emphasizes a future where there is a strong focus on economic development but also leads to high greenhouse gas emissions due to continued reliance on fossil fuels. The implications of SSP5 highlight the relationship between socio-economic trends and potential climate outcomes, providing insight into how these dynamics might influence future emissions scenarios.
Vulnerability Assessment: A vulnerability assessment is a systematic process used to identify, evaluate, and prioritize vulnerabilities within a system, community, or region, particularly in relation to climate change and its potential impacts. This process helps in understanding how susceptible specific areas or populations are to climate-related risks, such as rising sea levels, extreme weather events, and food insecurity. It plays a crucial role in developing effective strategies for mitigation and adaptation in the face of future greenhouse gas emissions scenarios.