Climate Change 315

What is a climate proxy?

Indirect evidence used to understand past climate.

What five climate proxies were covered?

Ice cores, ocean cores, coral, tree rings, and pollen.

Which proxy has annual temporal resolution?

Tree rings.

What is the temporal resolution of ice cores?

Seasonal to decadal.

How far back can ice cores record climate?

Hundreds of thousands of years.

What is the temporal resolution of ocean cores?

Centuries to millennia.

How far back can ocean cores record climate?

Hundreds of thousands of years.

What is the temporal resolution of coral records?

Monthly to decadal.

How far back can coral records extend?

Thousands of years.

What is the temporal resolution of pollen records?

Decades to centuries.

How far back can pollen records extend?

Hundreds of thousands of years.

What happens to lighter oxygen isotopes during evaporation?

They evaporate more readily than heavier isotopes.

During cold periods, what happens to ocean oxygen-18 concentrations?

They increase as more oxygen-16 is trapped in polar ice.

During warm periods, what happens to ocean oxygen-18 concentrations?

They decrease as less ice traps oxygen-16.

What biological process causes seasonal atmospheric CO₂ fluctuations?

Photosynthesis and respiration.

When are atmospheric CO₂ concentrations generally highest?

Winter, when photosynthesis is reduced and respiration continues.

What is assisted migration?

Human-mediated movement of species beyond their historical ranges to help them persist.

What is the main goal of assisted migration?

Reduce extinction risk when species cannot track suitable climates naturally.

What is a major ecological risk of assisted migration?

Introduced species may become invasive or disrupt recipient ecosystems.

What is aggressive assisted migration?

Extensive translocation beyond current ranges, acting before all facts are known.

What is constrained assisted migration?

Science-supported translocation with risk assessment and management plans.

What is avoidance of assisted migration?

Not translocating; instead protecting populations and improving connectivity.

What is a key risk of avoiding assisted migration?

Species may go extinct if they cannot adapt or disperse.

What factors guide assisted migration decisions?

Extinction risk, feasibility, benefits, biological risks, and socioeconomic costs.

What is a climate forcing?

A factor that alters energy received or reradiated by Earth.

Give examples of natural climate forcings.

Solar variation, orbital changes, and volcanic activity.

Give examples of human climate forcings.

Fossil fuel use, industrial activity, and agriculture.

What enzyme catalyzes carbon fixation in C3 plants?

Rubisco, which also catalyzes photorespiration.

Why does high temperature disadvantage C3 photosynthesis?

Rubisco favors oxygenation, increasing photorespiration and CO₂ loss.

Where does C3 carbon fixation occur?

Rubisco fixes CO₂ directly in the Calvin cycle.

What enzyme performs initial CO₂ fixation in C4 plants?

PEP carboxylase in mesophyll cells.

How do C4 plants reduce photorespiration?

They concentrate CO₂ in bundle sheath cells for the C3 pathway.

When are C4 plants generally favored?

Higher temperatures and lower CO₂ concentrations.

When are C3 plants generally favored?

Lower temperatures and higher CO₂ concentrations

Why do C4 plants use less water than C3 plants?

They can keep fewer stomata open while maintaining photosynthesis.

Which photosynthesis type uses the least water per gram?

CAM, followed by C4, then C3.

How does elevated CO₂ generally affect C3 plants?

It can increase photosynthesis by reducing photorespiration.

Realized niche

the actual set of environmental conditions, habitats, and resources that a species occupies and uses in nature

Fundamental niche

the full range of environmental conditions, resources, and habitats in which a species could theoretically survive, grow, and reproduce in the absence of biotic pressures like competition or predation

How do seasonal temperature ranges generally differ between temperate and tropical regions?

Temperate regions have greater seasonal temperature variation; tropical regions have less.

Why can phenology help track climate niches more easily in temperate regions?

The greater seasonal temperature gradient makes seasonal timing more informative.

Why can warming increase absolute thermal extremes more in the tropics?

Tropical temperatures have a narrow distribution, so warming can greatly expand the tail above a fixed threshold.

Why can relative thermal extremes respond strongly in temperate regions?

Temperate regions have broader temperature distributions, so warming shifts the relative distribution differently than in the tropics.

Where have recent absolute metabolic changes been larger, and why?

In tropical regions, because metabolism increases exponentially with temperature and starts at higher rates.

Where can relative metabolic changes be larger, and why?

In temperate regions, because lower baseline metabolism can undergo a large proportional increase with warming.

How can tropical and temperate species differ in climate-change vulnerability?

Different temperature distributions and seasonal patterns can lead to different exposure and biological responses.

What is the key distinction between absolute and relative change?

Absolute change is a raw difference; relative change is the difference compared with the starting value.