Planetary Boundaries 2023 lectura2

Page 1: Planetary Boundaries Framework Update

Authors

  • Katherine Richardson, Will Steffen, Wolfgang Lucht, Jørgen Bendtsen, Sarah E. Cornell, Jonathan F. Donges, Markus Drüke, Ingo Fetzer, Govindasamy Bala, Werner von Bloh, Georg Feulner, Stephanie Fiedler, Dieter Gerten, Tom Gleeson, Matthias Hofmann, Willem Huiskamp, Matti Kummu, Chinchu Mohan, David Nogués-Bravo, Stefan Petri, Miina Porkka, Stefan Rahmstorf, Sibyll Schaphoff, Kirsten Thonicke, Arne Tobian, Vili Virkki, Lan Wang-Erlandsson, Lisa Weber, Johan Rockström.

Key Points

  • Planetary Boundaries Framework: Update reveals that six out of nine planetary boundaries are transgressed, indicating Earth is outside the safe operating space for humanity.

    • Ocean acidification is nearing its critical level; regional aerosol loading exceeds its threshold.

    • Stratospheric ozone levels show a slight recovery.

    • Increased transgression levels for boundaries already identified as overstepped.

  • Human Appropriation of Net Primary Production (HANPP): Proposed as a new control variable affecting global biosphere functions.

Introduction

  • Planetary Boundaries Concept: Based on Earth system science, delineates nine critical processes necessary for Earth's stability.

    • Respecting these boundaries is vital to maintain a stable climate akin to that of the past 10,000 years (the Holocene).

    • Anthropogenic activities have pushed Earth beyond Holocene variability, entering the proposed Anthropocene epoch.

  • Paleoclimate Context: Historical evidence suggests that significant environmental changes impact the biosphere.

    • The report stresses the need to avoid excessive perturbations that could destabilize global environmental conditions.

Anthropogenic Forcings

  • Human activities introduce additional forcing effects on Earth’s systems, necessitating consideration of the anthroposphere within the planetary framework.

Page 2: Holocene as Reference State

Significance of the Holocene

  • Benchmark Reference: The Holocene is characterized by stable climate conditions that enabled the development of agriculture and societies.

    • Climate varied very little during this period (±0.5°C).

    • Boundaries are set against pre-industrial Holocene conditions to assess anthropogenic deviations effectively.

Framework Development and Governance

  • Established boundaries serve to guide governance and policy frameworks addressing global environmental changes.

  • Continuous updates are made as new scientific understanding emerges.

Control Variables and Cumulative Transgressions

  • Control variables are developed to assess the potential impacts of crossing boundaries, often drawing from regional data to establish global phenomena.

  • The significance of aggregating transgression data across multiple regional systems is emphasized.

Page 3: System Interactions and Challenges

Understanding Interactions

  • Emphasizes a need for integrated Earth system models that connect biosphere, anthroposphere, and geosphere processes.

    • Interactions define responses and can lead to nonlinear consequences on Earth systems.

  • Core Boundaries: Climate change and biosphere integrity are termed core boundaries with interlinked risks.

Progress and Challenges

  • While quantifying interactions between boundaries is challenging, advances have been made.

  • Studies suggest that exceeding core boundaries, such as those related to climate or biodiversity, amplifies risks for other boundaries.

Modeling and Scenario Analysis

  • Focus on exploring transgressions of land and climate boundaries and their relationships to carbon storage and temperature.

Page 4: Biosphere Integrity and Control Variables

Biosphere's Role

  • The biosphere significantly interacts with the geosphere to regulate global environmental conditions.

    • Genetic diversity and functionality are essential for a stable biosphere.

Setting Biosphere Integrity Boundaries

  • Current rate of extinctions exceeds pre-industrial levels; estimates suggest >100 extinctions per million species-years (E/MSY) currently.

  • Provisional boundary set for functional biosphere integrity at 10% of pre-industrial mean NPP, with high-risk thresholds set at 20%.

Page 5: Current Status of Planetary Boundaries

Earth System Process

Control Variable(s)

Planetary Boundary

Preindustrial Base Value

Current Value

Climate Change

Atmospheric CO2 (ppm)

350 ppm CO2

280 ppm CO2

417 ppm CO2

Biosphere Integrity (Genetic)

Extinction Rate (E/MSY)

<10 E/MSY

~1 E/MSY

>100 E/MSY

Stratospheric Ozone Depletion

Ozone Concentration (DU)

<5% reduction

290 DU

284.6 DU

Ocean Acidification

Carbonate Ion Concentration (Ωarag)

>80% Ωarag

3.44 Ωarag

2.8 Ωarag

Note: Several other critical values indicated as transgressed.

Page 6: Freshwater Change and Its Impact

Freshwater Boundary Updating

  • The freshwater boundary has been revised to better capture alterations to the entire water cycle over land.

    • Both blue and green water components have established boundaries; current deviations suggest transgression.

Page 7: Novel Entities and Ozone Depletion

Novel Entities Boundary

  • Defined as anthropogenic substances not naturally found in the Earth system (e.g., microplastics, radioactive waste).

  • Strong evidence indicates the boundary is currently transgressed due to the release of untested synthetic compounds.

Ozone Depletion Performance

  • Some recovery noted in stratospheric ozone due to policies like the Montreal Protocol, currently within safe limits.

Page 8: Aerosol Loading and Its Effects

Aerosol Impacts

  • Anthropogenic aerosols have significant climate impacts, but defining boundaries is complex due to their varied sources and effects.

  • Current measures indicate that specific regional boundaries have been transgressed.

Page 9: Ocean Acidification and Land System Change

Ocean Conditions

  • Ocean acidification nearing critical levels; a comprehensive assessment is needed for long-term impacts on marine ecosystems.

  • Land system changes have implications for forested areas; deforestation trends are increasing, especially in tropical forests.

Page 10: Climate Change Impact Models

Climate and Land Systems Modeling

  • Studies suggest that human activities have historically kept the climate system pushed beyond safe limits since the late 20th century.

  • Carbon dynamics modeling indicates significant risks associated with current deforestation rates and greenhouse gas emissions above modeled thresholds.

Page 11: Data Considerations and Challenges Ahead

Future Modeling Requirements

  • Need for developments in Earth system models that encompass complex interactions between various spheres.

  • Focus on understanding how ecological processes impact the overall resilience of Earth systems.

Page 12: A Call for Action

  • The planetary boundaries framework serves as a guiding tool for humanity to innovate positively while ensuring Earth's stability.

  • Urgent actions are required to transition sustainably, avoiding irreparable damage to global systems, stressing importance for integrated policy approaches.