EVSC 100 - Final Exam

What is climate?

The long-term average of weather over ≥30 years.

What is weather?

Short-term atmospheric conditions at a given place and time.

What causes anthropogenic climate change?

Human emissions of greenhouse gases that alter Earth’s energy balance.

What is the natural greenhouse effect?

Natural GHGs trap longwave radiation and keep Earth warm.

What is the human-enhanced greenhouse effect?

Extra GHGs from human activities trap additional heat → warming increases.

Main anthropogenic greenhouse gases

CO₂, CH₄, N₂O.

Control variable for climate change

Atmospheric CO₂ concentration (ppm).

Planetary boundary for climate change

350 ppm CO₂.

Current CO₂ concentration

Over 420 ppm.

Ice core evidence for human-caused climate change

CO₂ stayed below ~280 ppm for 800,000 years until it spiked after 1850 due to fossil fuel burning.

Why ice cores prove humans are responsible

They contain trapped ancient air showing CO₂ rises only after industrialization, with fossil fuel carbon isotope signatures.

Mitigation actions

Reduce fossil fuels, electrify transport, protect forests, use Nature-Based Solutions, improve efficiency.

Biosphere Integrity control variables

Extinction rate (genetic diversity) and functional diversity.

Biosphere planetary boundary

≤10 extinctions per million species per year.

Current extinction rate

100–1000× higher than background rate.

Definition of biodiversity

Variety of life across genes, species, and ecosystems.

How biodiversity supports resilience

More species → more redundancy → faster recovery from disturbance.

Definition of ecosystem

Interactions among organisms and their physical environment.

Ecosystem functions

Internal ecological processes (energy flow, decomposition, nutrient cycling).

Ecosystem services

Human benefits from ecosystems (pollination, water purification, carbon storage).

Definition of keystone species

A species with a disproportionately large impact on ecosystem stability.

Definition of apex predator

The top predator in a food web with no natural predators.

Definition of habitat

The physical environment where a species lives.

Definition of niche

The ecological role or function of a species.

Trophic cascade definition

Changes at one trophic level causing effects throughout the ecosystem.

Yellowstone trophic cascade example

Removing wolves → elk overbrowse → plants decline; reintroducing wolves → vegetation recovers.

Land-use definition

How humans use land (agriculture, cities, logging, mining).

Control variable for land system change

% of original forest cover remaining.

Planetary boundary for forest cover

75% forest cover remaining.

Current forest cover

~62%, meaning the boundary is exceeded.

Main drivers of deforestation

Agriculture, logging, mining, fires, ranching, population growth.

Why forests are key to Earth systems

Regulate climate, store carbon, maintain rainfall, support biodiversity.

Ecosystem services of rainforests

Carbon storage, rainfall generation, oxygen production, biodiversity, medicines.

Definition of resilience (forests)

Ability of a forest to recover from disturbances like fire or drought.

Amazon feedback loop

Deforestation → less evapotranspiration → less rain → more drought → more fires → more forest loss.

Boreal/permafrost feedback loop

Warming → permafrost thaw → methane release → more warming.

How land system change links to other boundaries

Forest loss → more CO₂ (climate), habitat loss (biosphere), nutrient cycle disruption (biogeochemical flows).

Definition of sustainability

Meeting present needs without compromising future generations.

Nature-Based Solutions definition

Using ecosystems to solve climate, biodiversity, and social challenges.

Why Nature-Based Solutions are effective

Provide ~37% of needed climate mitigation by 2030; low cost; multiple co-benefits.

Examples of Nature-Based Solutions

Forests, wetlands, mangroves, urban green spaces, agroforestry.

Definition of green infrastructure

Urban nature-based engineering like rain gardens, green roofs, and swales.

Benefits of urban green spaces

Reduce heat, improve air quality, support biodiversity, improve mental health.

Definition of biome

Large ecological region defined by climate, vegetation, and characteristic species.

How climate change affects biomes

Causes biome shifts (northward, upward), species range changes, and biome loss.

Two key ecosystem processes

Energy flow (sun → producers → consumers) and nutrient cycling.

Energy flow definition

Unidirectional movement of energy through ecosystems from the sun through trophic levels.

Nutrient cycling definition

Cyclic movement of nutrients through biotic and abiotic components.

Four planetary spheres

The atmosphere, biosphere, hydrosphere, and geosphere.

Atmosphere definition

Layer of gases surrounding Earth influencing climate and weather.

Hydrosphere definition

All water on Earth (liquid, solid, and vapor).

Biosphere definition

All living organisms and their interactions.

Geosphere definition

Solid Earth (rocks, soil, tectonics, landforms).

Definition of anthropogenic

Human-caused.

Definition of evapotranspiration

Water transfer from soil and plants to the atmosphere.

Definition of radiative forcing

Change in Earth's energy balance caused by GHGs.

Definition of feedback loop

A process that amplifies or dampens environmental change.

Definition of carbon sink

System that absorbs more carbon than it emits.