D4.3 Climate change

The greenhouse effect

When radiation from the sun hits the earth, it is radiated back from the Earth’s surface. Greenhouse gases absorb this re-radiated radiation, trapping it in the Earth’s atmosphere. They have an insulating effect

Anthropogenic climate change

Changes in Earth's climate caused by human activities

Industrial revolution and atmospheric carbon dioxide

Increasing levels of carbon dioxide since the industrial revolution and increasing global temperatures

Anthropogenic sources of atmospheric carbon dioxide

Burning of fossil fuels, when natural sources of carbon (carbon sinks) are damaged or destroyed (deforestation, soil degradation, peat harvesting)

Anthropogenic sources of atmospheric methane

Released from the guts of ruminant animals, landfill sites (when food waste decomposes), extraction of fossil fuels from underground

Positive feedback

Any mechanism in a system that leads to additional and increased change away from the equilibrium

5 examples of positive feedback related to global warming

Loss of reflective snow and ice (ice caps melt and more light energy is absorbed by exposed rock), decomposition (as global warming increases, rates of decomposition increase, releasing carbon dioxide), melting permafrost (microorganisms in permafrost produce methane in metabolism), drought and forest fires (droughts are more often, fires are more likely, releases carbon dioxide, reduction in plants means less carbon dioxide is removed)

Tipping point

When an ecosystem switches from being a carbon sink to being a carbon source due to the effects of global warming

The reduction in water availability for boreal forests

Less snow falls due to increased temperatures, meaning less water is available, leading to drought, reducing photosynthesis. Risk of forest fires increases as trees die and dry out

Legacy carbon

Carbon which has been stored in ecosystems for a long time

Effect of legacy carbon combustion

Can tip the forests from a source to a sink, and can be irreversible

Problems of climate change for emperor penguins

Emperor penguins breed on antarctic sea ice, laying and incubating their eggs, and raising their young. The early melting of ice does not give them enough time to raise their young

Problems of climate change for walruses

Walruses rely on Arctic sea ice, where mothers can feed their young and hunt for food nearby. The early melting of ice means that nursing mothers need to travel longer to the water's edge, leaving young without protection for longer periods

What are ocean currents driven by?

Wind, temperature, salinity gradients

What do ocean currents do?

They redistribute heat across Earth's surface. Warm ocean currents carry heat from the tropics towards the poles. Cold ocean currents transport cold water from polar regions towards the tropics

Upwelling

Occurs when colder, nutrient-rich water rises to the surface as a consequence of wind and wave movement, displacing warmer surface water. This supports marine life

Effect of climate change on upwelling

Warm surface water prevents nutrient upwelling by creating a more stable ocean stratification, reducing primary production and the flow of energy through marine food chains

Poleward shift

The movement of a species’ geographical range towards the Earth's poles as a response to changing climate conditions

Upslope shift

The movement of a species’ geographical range towards higher altitudes as a response to changing climate conditions

Coral polyps and algae

Coral polyps live in a symbiotic relationship with algae, where algae provides carbon compounds through photosynthesis and the polyp provides shelter and protection

Threats of climate change to coral reefs

The death of coral polyps will have a knock-on effect on species that rely on the reef, disrupting food webs, reducing the availability of niches and reef biodiversity. Many species will die off or migrate to other habitats, leading to ecosystem collapse

Ocean acidification

CO₂ + H₂O → H₂CO₃ 

H₂CO₃ → H⁺ + HCO₃^-

HCO₃^- → H⁺ + CO₃^2-

As more carbon dioxide dissolves in seawater, more carbonic acid forms and dissociates, and more hydrogen carbonate ions form and dissociate, the end result is increasing numbers of hydrogen ions. This causes the ocean to become more acidic

Consequences of ocean acidification

The calcium carbonate exoskeletons of corals can be weakened and even dissolve. The reaction during which hydrogen carbonate ions dissociate to form hydrogen ions and carbonate ions reverses to buffer the increasing number of hydrogen ions, reducing the availability of carbonate ions for the building of hard exoskeletons

Coral bleaching

High water temperatures cause coral polyps to expel their algae symbionts, causing the reefs to lose their bright colours and leads to coral bleaching. Because the polyps rely on the algae forcarbon compounds, extended bleaching can lead to the death of the polyps

Carbon sequestration

The process of capturing and storing carbon dioxide from the atmosphere

Forest regeneration

Involves replanting new trees in deforested areas

Afforestation

The creation of new forests by planting trees in areas that haven’t been forested for a long time

Peat bog restoration

Peat bogs form when plant matter cannot decompose fully due to waterlogged (anaerobic) and acidic conditions. They are a carbon sink. Regulating peat harvesting and drainage allows peat bogs to recover and grow in depth, increasing their ability to sequester carbon

Phenology

The study of the timing of biological events

Variables that impact phenology

Temperature, day length (photoperiod)

Cause and consequences of phenological changes

If events do not occur at the right time, species will be left without the resources that they need, and food chains will be disrupted. Trophic levels may be missing from the food chain. The consumer species' life cycle no longer aligns with the peak availability of its food resource (trophic mismatch)

Arctic mouse-ear chickweed & migrating reindeer

Reindeer are migratory mammals, and they rely on day length as the environmental cue for seasonal migration. Arctic mouse-ear chickweed is a plant that forms part of the diet of reindeer; its peak productivity is determined by temperature signals. The mismatch between migration timing and availability of arctic mouse-ear chickweed due to climate change can affect the ability of reindeer to breed successfully, as they are unable to breed and raise their young

Great tits & caterpillars

The great tits need the greatest biomass of caterpillars around 9 days after their chicks hatch. As a result of global warming, caterpillar biomass peaks around 2 weeks earlier and egg hatching peaks around 1 week earlier, creating a temporal mismatch between the hatching of chicks and the availability of food, reducing breeding success

Climate change and the spruce bark beetle

Spruce bark beetles lay their eggs under the bark of spruce trees; they occur in Europe and North America. They feed and mature under the bark of trees, causing damage and sometimes killing the trees when high numbers of beetle larvae are present. Eggs hatch into larvae which feed from tree phloem and other tissues. Larvae pupate into adult beetles. Beetles emerge from the bark and the cycle repeats. This life cycle can occur once or twice a year, but higher temperatures mean more than two are more likely to occur

Evolution in tawny owls due to climate change

There are 2 variants of tawny owls, some are grey and some are brown. In a snowy environment, grey owls are less visible, so are more successful and are more likely to survive and reproduce. Global warming and milder winters mean that there is less snow, and brown owls have increased success. They are more likely to survive, reproduce and pass on their alleles for brown feathers