Notes on Climate Change Lecture

Introduction

Earth system scientists and climate scientists express serious concerns about rapid changes in the planet.
Risks of abrupt changes are being underestimated.
Planetary Boundary Framework introduced 15 years ago: outlines nine Earth system processes essential for stability and resilience.
Paris Agreement signed 10 years ago, marking a commitment to combat climate change.
Current decade is crucial for determining the future of the planet.

Global mean surface temperature has risen to 1.2°C, the warmest in the past 100,000 years.
Acceleration in warming observed:
- 0.18°C increase per decade (1970-2010)
- Jump to 0.26°C per decade (from 2014)
Projections:
- Likely to exceed 2°C within 20 years.
- Potential to reach 3°C by 2100.

Climate change is causing significant disruptions:
- Increased droughts, floods, heat waves, and human health issues.
- Estimated 40°C heat in 2023 leads to severe human consequences (e.g., deaths during Hajj pilgrimage).
Economic costs are increasing:
- Up to $200 billion/year in the U.S. alone.
- Predictions of 18% loss of GDP by 2050, equivalent to $38 trillion/year.

Buffering capacity is the Earth's ability to absorb shocks, now declining.
Tipping points refer to critical thresholds in Earth systems that, if crossed, can lead to irreversible changes.
Examples of tipping element systems:
- Green and West Antarctic ice sheets.
- Amazon rainforest at risk of tipping to a savannah state.

Oceans absorb 90% of heat from climate change.
Recent data shows unprecedented increases in sea surface temperatures.
Energy imbalance due to human activities is alarming:
- Heat absorbed equivalent to 300 times global electricity use in one year.

16 tipping elements identified in climate science, with varying degrees of risk.
Five elements likely to tip at 1.5°C:
- Green and West Antarctic ice sheets, loss of tropical coral reefs.
Increasing scientific understanding correlates with a greater risk of tipping points.

Urgent actions needed to stay under 1.5°C:
- Only 200 billion tons of CO2 remaining in the carbon budget for a 50% chance of limiting warming to 1.5°C.
- Must reduce emissions by at least 7% per year to achieve net-zero by 2050.
Breaching the 1.5°C limit likely between 2030-2035 with an overshoot predicted.

Expect more severe climate impacts if current trends continue.
Planet must remain healthy to absorb carbon and prevent tipping points.
Need to maintain planetary boundaries across various Earth system processes.
Solutions available for a sustainable future include:
- Rapid transition from fossil fuels.
- Circular business models.
- Sustainable food systems and regeneration of natural ecosystems.
Citizens worldwide show concern for climate and demand solutions.

The challenge is daunting, yet feasible.
Emphasizes the importance of collective action and commitment to sustainable practices.
Recognizes a growing global awareness and willingness to address climate change.