Curbing Climate Change & Its Impacts – Lecture Vocabulary

Learning Outcomes

• Be able to define climate change.
• Describe the physical causes (greenhouse-gas buildup, industrialization, etc.).
• Explain the impacts – direct, indirect, cascading – on natural and human systems.

Recap of Previous Lecture

• Grand Challenges in Environmental Engineering introduced last week.
  • First challenge: Sustainably supply food, water & energy within the Food-Water-Energy Nexus.
• Current & next two classes tackle the second challenge: Curb climate change & adapt to its impacts.

What Students Should Study

• Focus on the learning-outcome list for each lecture.
• Homework questions mirror likely quiz/exam content.

Defining Climate Change

• “A change in the state of the Earth’s climate that
  • Persists for an extended period (decades to millennia).
  • Is identified by shifts in climatic properties (temperature, gas composition, ice cover, etc.).”
• Distinguish from weather variability: climate change is directional & essentially irreversible on human time-scales.

Earth’s Five Interacting Climate Spheres

• Atmosphere – gaseous envelope; composition & temperature can shift.
• Hydrosphere – liquid water (oceans, lakes, rivers).
• Cryosphere – frozen water (snow, glaciers, sea ice).
• Lithosphere – solid Earth’s crust; stores carbon, influences albedo.
• Biosphere – all living organisms responding to climatic context.
• Climate change may alter one, several, or all of these spheres simultaneously.

Natural vs Anthropogenic Climate Change

• Planet is 4.6\text{ billion years} old.
• Geological record shows multiple eras, periods, epochs (Ice Age, Pliocene, etc.).
• Natural transitions normally occur over millions of years, allowing gradual adaptation.
• Current epoch: Holocene (stable conditions favourable to modern humanity).
• Today’s warming differs because it is rapid (decades–centuries instead of millennia) and human-driven.

Observed Modern Warming

• NASA temperature anomaly visualization: consistent rise from 0 to +2^\circ\text{C} over recent decades.
• Ten of the last 13 years are the warmest on record.
• Average global temperature increase over past century: 1.2$–$1.4^\circ\text{F} (\approx0.7$–$0.8^\circ\text{C}).

Greenhouse Effect Refresher

• Greenhouse gases (GHGs) absorb & re-emit infrared radiation, acting like a thermal blanket.
• Natural GHGs = good; excess GHGs = enhanced greenhouse effect → warming.

Empirical Evidence Linking GHGs & Temperature

• Graph 1: Atmospheric \text{CO}2, \text{CH}4, \text{N}_2\text{O} relatively flat for millennia, then spike post-1800.
• Graph 2: Same time axis shows global mean temperature tracking the \text{CO}_2 curve.
• Industrial Revolution (~1750$–$1850) marks divergence point.

IPCC Consensus

• Intergovernmental Panel on Climate Change (IPCC): “It is unequivocal that human influence has warmed the atmosphere, ocean, and land.”
• 97 % of climate scientists concur.

Composition of Global GHG Emissions (Latest IPCC AR6)

• 65\% \text{CO}_2 (fossil fuel & industrial processes).
• 11\% \text{CO}_2 (land-use change/deforestation).
• 16\% \text{CH}_4 (agriculture – enteric fermentation, rice, waste).
• 6\% \text{N}_2\text{O} (agro-soils, fertilizers).
• 2\% Fluorinated gases (refrigerants, speciality industries).

Emissions by Sector

• Energy supply (electricity & heat): 20\%.
• Industry & manufacturing: 12\%.
• Agriculture, forestry & land use: 10\% direct, plus land-use tensors above.
• Transport: 8\% (road, aviation, shipping).
• Buildings: 3\% (operational energy, materials like cement/steel).
• Waste: smaller but significant methane source.

Emissions by Geography (approx.)

• China, USA, EU, India dominate distinct slices.
• “Rest of World” (incl. NZ) comparatively small, though equity debates persist because vulnerable regions are not always the highest emitters.

Rapid-Rise Fact-Check (Class Quiz)

1. CO₂ rise speed: emissions have risen ≈10× faster in last 19 yr than any rise in previous 800{,}000 yr – TRUE (five-times claim was an underestimate).
2. Arctic Ocean ice-free by 2100? – FALSE strictly; with 1.5^\circ\text{C} warming, ice-free summers likely once per century; at 2^\circ\text{C} warming → once per decade.
3. Storm Intensity Increase – TRUE. Warmer oceans evaporate more moisture→ stronger hurricanes, cyclones, typhoons.

Paris Agreement Temperature Limits

• Goal: keep warming “well below” 2^\circ\text{C} and pursue 1.5^\circ\text{C} relative to pre-industrial (≈1850) baseline.
• Rationale: Even 0.5^\circ\text{C} difference drastically alters risk profiles (ice-free decades vs centuries, flood frequency, etc.).

Direct Physical Indicators of a Warming World

• ↑ Air temperature (over land & ocean).
• ↑ Sea-surface temperature.
• ↑ Ocean heat content & acidity; pH drop of ≈30 % since late 18th C.
• ↑ Humidity.
• ↑ Sea level: +6.7\,\text{in} in 20th C, rate doubling in past decade; thermal expansion + land-ice melt.
• ↓ Glaciers, ice sheets, sea-ice extent & thickness.
• Seasonal shifts: earlier springs, altered snow cover duration.

Cascading & Indirect Impacts

• Ocean acidification → coral bleaching, shell dissolution → disrupts marine food webs; jeopardises protein for ≈1\text{ billion} people.
• Extreme weather → human injury, trauma, infrastructure loss.
• Flood–drought polarity: wet regions wetter, dry regions drier.
• Agricultural disruption: yields depend on predictable rainfall/temperature.
• Vector ecology shifts → spread of malaria, dengue, etc.
• Heat stress → cardiovascular, respiratory illness; labour productivity drop.
• Sea-level rise threatens \sim72{,}000 NZers now; +10\,\text{cm} exposes ~7{,}000 more buildings each increment.
• Engineering challenge: historical design codes assume stationary hazard statistics; climate change makes them non-stationary.

Indigenous & Local Knowledge as Risk Tools

• Māori tiny fae/taniwha stories store empirical flood & hazard data.
• 2005 Matatā flash-flood: cultural siting of marae avoided damage.
• Combining traditional ecological knowledge (TEK) with modern science improves hazard mapping & adaptation strategies.

Ethical, Equity & Practical Dimensions

• Emitters vs sufferers: High-income nations produce most GHGs; low-lying islands & least-developed countries face existential risks.
• Questions of managed retreat, insurance retreat, community relocation – cultural survival intertwined with geography.

Personal & Societal Mitigation Actions (Video Recap)

• Recycle/re-use; conserve energy (switch off devices).
• Low-carbon mobility: walk, cycle, public transport.
• Dietary shift: eat less meat, more local plants.
• Knowledge sharing & advocacy – amplify urgency.

Engineering Relevance & Forward Look

• Need to design for changing hazard magnitudes & frequencies.
• Interdisciplinary solutions: materials, energy systems, water, transportation.
• Tomorrow’s lecture will continue with adaptation strategies & engineering responses.

Summary (Key Takeaways)

• Current climate change = rapid global warming driven by anthropogenic GHGs.
• Greenhouse gas concentrations & global temperature are tightly correlated; inflection at Industrial Revolution.
• Dominant GHG = \text{CO}_2 from fossil fuels; main sectors energy, industry, agriculture, transport.
• Impacts range from physical indicators (ice melt, sea-level rise) to complex cascading effects (food security, health, cultural loss).
• Limiting warming to 1.5$–$2^\circ\text{C} critical; even 0.5^\circ\text{C} difference magnifies risks.
• Adaptation & mitigation require integration of science, engineering, policy, and indigenous knowledge.

Extra Resources (recommended by lecturer)

• “Climate Change – The Facts” (BBC documentary).
• IPCC Sixth Assessment Report (AR6) Working Group I Summary for Policymakers.
• “The Spinoff” NZ climate video series (esp. segment on sea-level rise & tiny fā guardianship).
• NASA GISTEMP & NOAA Climate Dashboards for up-to-date data.
• Paris Agreement full text & NZ’s Nationally Determined Contribution (NDC).