Lecture 1: climate and climate change

Question 1

Climate extremes

Answer 1

• Tend to affect the Global South disproportionally large
• They will likely aggravate with climate change

Question 2

The Global circulation pattern

Answer 2

• Differential solar heating creates global temperature gradients.
• At the equator, hot air rises (ITCZ), then spreads north/south at the tropopause.
• Cold air sinks at the poles; the Coriolis force due to Earth’s rotation leads to 6 circulation cells:
• Hadley cells (dominant in tropics).
• Ferrel cells (mid-latitudes).
• Polar cells.

Question 3

Influence global circulation patterns on rainfall and wind patterns

Answer 3

• Rising air cools adiabatically → condensation → rainfall (esp. ITCZ).
• Convective rainfall in tropics; frontal rainfall in temperate zones.
• Descending air creates dry, high-pressure zones (e.g. deserts).
• Surface winds are deflected due to Coriolis force:
  → Eastward when moving poleward.
  → Westward when moving equatorward.
• Winds affect rainfall by transporting moist air from oceans (esp. via anticyclones).

Question 4

Seasonal variation

Answer 4

Earth’s axial tilt causes solar radiation zones (ITCZ) to shift seasonally.
This leads to strong seasonal rainfall contrasts, especially across Africa.

Question 5

Climate change - the greenhouse effect

Answer 5

Natural phenomenon where greenhouse gases (GHGs) trap heat.
Human activities (fossil fuels, land use change) intensify this effect.
Major GHGs: CO2, CH4, N2O.

Question 6

Climate change - who’s responsible

Answer 6

• China, USA, and Europe emit >50% of global CO2.
• Africa emits only ~3.7%.
• Per capita emissions vary starkly: US > 14.8 tons/year vs. DR Congo ~0.03 tons.
• Emissions correlate with GDP but also show inequality.
• Cumulative emissions show historical dominance by USA and Europe.
• There is a slight shift towards more emissions from emerging economies.
• Still, per capita emissions have begun to plateau or decline in some regions.

Paris Agreement and Policy Impact
* Current policies are insufficient to limit warming to <2°C.
* Optimistic scenarios (e.g. full Paris implementation) still require massive action.

Question 7

Why Staying Below 2°C Matters (S.H.I.T. framework)

Answer 7

Why Staying Below 2°C Matters (S.H.I.T. framework)

• Slow onset changes: sea level rise, glacier melt, biodiversity loss.
• Hazards: more frequent/intense floods, droughts, storms, etc.
• Increased variability, uncertainty, ENSO disruption.
• Trends: deeper poverty, undernutrition, poor health due to affected livelihoods.

Positive Feedback Loops
E.g. warming peatlands, melting permafrost, dieback of Amazon, loss of ocean CO2 sink.

Question 8

Spatial Variation in Climate Impacts

Answer 8

Spatial Variation in Impacts
* More extreme heat days (e.g. Mora et al. 2017).

Changes in rainfall dynamics:
-> More intense rain due to higher moisture storage.
-> Seasonal shifts.

• Water availability uncertainties (e.g. Sahel has short cropping seasons, high variability).
• Climate patterns like the ITCZ and West African Monsoon (WAM) are sensitive to sea surface temperatures and land use change.
• Ice melt could exacerbate vulnerabilities (e.g. Sahel).

Question 9

Vulnerability to climate change

Answer 9

Africa is highly vulnerable due to:
* Agricultural dependency.
* Low adaptive capacity (poverty, weak infrastructure/governance).

Climate change may increase the likelihood of violent conflict:
* Local economic shocks reduce opportunity cost of conflict.
* Climate-induced inequalities fuel grievances.
* Migration and urbanization increase competition over local resources.
* Altered logistics (e.g. road conditions) affect conflict dynamics.
* Cognitive stress and misattribution increase aggression.

Question 10

Intergenerational inequality

Answer 10

Need for New Perspectives
* Younger generations will face more impacts.
* Question of fairness in climate litigation.

Eulerian vs. Lagrangian Viewpoints
* Eulerian: fixed-point in time and space.
* Lagrangian: following a cohort through time (better for intergenerational analysis).

E.g. Walking behind someone who is smoking vs standing still
So far, most impact studies used an Eulerian approach

Question 11

Responses to climate change impacts

Answer 11

Mitigation: reduce greenhouse gas (GHG) emissions
→ REDD+: Reduced emissions from deforestation & land degradation

Adaptation: preparing to deal with the effects of climate change
→ Loss & Damage: Dealing with the impacts for which adaptation will not work

Question 12

Quatifying exposure in relation to age

Answer 12

The idea: integrate exposure of an ‘average person’ to extreme events across their lifetime
- Heatwaves:
→ Different climate scenario’s give very different outcomes for the younger generations, but not for the older ones
→ Under a 3.5°C warming scenario, a person born in 2020 will experience uo to 30x heatwaves than a person born in 1960
→ For the latter, climate change will have virtually no effect on the number of heatwaves experienced in their lives
- Can be done for other impacts by combining different sources of data

Geometric mean of all six extreme event types
→ The youth is screwed, older generations won’t face the risk

Question 13

Exposure Multiplication Across Lifetimes (Thiery et al., 2021)

Answer 13

Children born in 2020 will experience:
* Up to 30x more heatwaves than someone born in 1960.
* 6x more climate extremes (average across 6 event types).

Highest increases in Global South.
* Poor young people are most affected despite lowest contribution.
* Spatial injustice: more children are born in the most impacted areas.