Apes Unit 9: Global Change

Which form of light from the sun enters the troposphere from the stratosphere?

l. UV light

ll. Infared light (IV)

lll. visible light

ll & lll (IV, visible)

Ozone in the stratosphere absorbs what UV light?

UV-C and much of UV-B light

tropospheric ozone =

respiratory irritant, damaging to plant tissue, precursor to photochemical smog

human health benefits

• prevention of skin cancer & cataracts

• UV-B & C damage DNA (skin cancer) & can cause oxidative stress in eyes
  (cataracts)

• UV-B &C can also suppress human system

negative impacts of stratospheric ozone to plants

• UV-B & C damages plant cells reducing ability to perform photosynthesis

• Loss of plants/algae can cause breakdown of food web → loss of phytoplankton leads to no fish

how ozone forms in the stratosphere

UV light splits an oxygen molecule (O₂):
High-energy ultraviolet (UV-C) radiation breaks apart an oxygen molecule:

O₂ → (UV-C) → O + O

Free oxygen atoms react with O₂:
Each of those free oxygen atoms (O) can react with another O₂ molecule to form ozone (O₃):

O + O₂ → O₃

breakdown of stratospheric ozone

UV light splits an ozone molecule (O)

O₃ → (UV-C) → O₂ + O

two oxygen atoms bond to form O

O + O → O2

What is the replacement for HCFC’s?

HFC’s (GHG, but not ozone depleting (no Cl))

what is the replacement for HFC’s?

HFO’s (HFC’s with C-C double bonds that shorten atm lifetime & GWP)

HFO

hydrofluoroolefin

What is the primary anthropologic cause of O₃ breakdown?

CFC’s

Anthropologic ozone depletion

UV radiation separates a chlorine atom from CFCs

highly electronegative chlorine atoms bonds to one of the oxygen atoms of O₃ converting it to O₂

Free O atom the bonds to O from Cl monoxide to form O₂

Free Cl atom breaks down more ozone

Cl + O₃ → ClO + O₂

ClO + O → Cl + O₂

What circumstances cause polar stratospheric clouds (PSC) to form?

extremely cold temp. unique to the Antarctic stratosphere

natural ozone depletion

1. Antarctic winters (June to August)

   • extremely cold stratospheric temps., no sunlight

2. PSC forms

   • HCI + ClONO₂ → Cl₂

   • Cl₂ → Cl + Cl

3. during spring (Sep. - Nov.), sunlight returns & breaks down Cl₂. Cl atoms destroy O_3.

main way to reduce anthropologic O₃ depletion

phasing out and replacing CFC’s

Montreal protocol (87’)

global agreement to phase CFC’s out of production in refrigerators, aerosols, etc.

• replaced with HCFC’s (hydrogen with hydrogen added)

• HCFC’s still deplete O₃ and acts a GHG, but to a lesser degree than CFC’s

• not a Permanant solution, by a temporary transitioning option (phase out

How much solar radiation is reflected back into space by clouds & atmosphere?

26%

How much solar radiation is absorbed by atmosphere & clouds & radiated out into space & own to earth?

19%

the greenhouse effect

Gases in earth’s atmosphere trap heat from the sun & radiate it back down to earth

• Without greenhouse effect, earth would be too cold to support life

how does the greenhouse effect work?

• solar radiation (light waves like UV & visible light) strike earth surface, heating it up

• earth’s surface releases Infared radiation

  GHGs absorb infrared radiation & radiate it both out into space and back toward earth

• portion coming back to earth is the greenhouse effect

Most important GHGs

• CO₂

• CH₄ (methane)

• N₂O (nitrous oxide)

• CFCs/HCFCs/HFCs

CO₂

FF combustion, decomposition, deforestation

CH₄ (methane)

natural gas extraction & combustion, animal agriculture, anaerobic decomposition (esp. permafrost thaw)

N₂O (nitrous oxide)

agricultural soils (denitrification of nitrate, esp. in overwatered, over fertilized soils)

global warming potential (GWP)

measure of how much a given molecule of gas can contribute to the warming of the atm. over a 100-year period, relative to CO2

What is GWP based off of?

• residence time

• infrared absorption

residence time

how long molecule stays in the atmosphere

infrared absorption

how well the gas absorbs & radiates Infared radiation (IR)

CO₂ GWP

1

CH₄ GWP & residence time

• 23-84

• 12 years

N₂O GWP & residence time

• 300

• ~ 115 years

CFCs GWP & residence time

• 1600 - 13000

• 50 - 500 years

Why is sea level rising?

• thermal expansion

• melting polar & glacier ice

thermal expansion

• water molecules move slightly further apart when they’re heated

• all the water molecules of ocean moving slightly apart leads to sea level rising

melting polar and glacial ice

• increased GHG leads to a warmer climate & more melting of ice sheets (at the poles & glaciers)

• this water flows into the ocean and leads to sea level rise

env. impacts of sea level rise

• flooding of coastal ecosystems like estuaries (mangroves, salt marshes)

• loss of species that depend on artic & tundra ecosystems (polar bears, penguins, reindeer)

• loss of thaw-freeze cycle that glaciers go through, depriving surrounding ecosystems and human communities of water source

human impacts of sea level rise

• relocation of coastal human pop.

• increase in flood frequency = higher insurance and repair costs, lost property

• saltwater intrusion (saltwater pushing into ground water & contaminating wells)

• refugees forced to move inland

vectors

living organisms (usually mosquitos, ticks, fleas) that can transmit diseases from human to human or animal to human

Ex. malaria, zika, west Nile, dengue fever

historic climate change

earth’s climate has varied over geologic time, largely due to variations in earth’s orbit around the sun

• varies in obliquity (~40,000 yrs.) exposing northern latitudes to higher insolation at different times

• varies in eccentricity (~100,000 yrs.) bringing it closer to and further from the sun at different times

  • more eccentric = further from sun

Milankovitch cycles

predictable variation in Earth’s climate

how have scientists been measuring/estimating earth’s historical temperature & CO₂ levels?

• foraminifera shells in ocean sediments - different species have different temp. tolerance

• air bubbles in ice cores that contain ancient atmospheric gas (CO₂ levels)

• ¹⁶ vs ¹⁸O isotope concentration in ancient ice

  • increased ¹⁸O = higher temp.)

effects of climate change

• rising temp. → habitat/species loss, drought, soil desiccation (drying), heat waves, increased precipitation in some regions

• rising sea levels → due to glacial, polar ice melt + thermal expansion

• melting of permafrost → permanent frozen tundra soils that begins to thaw & release methane & CO₂ from anaerobic decomposition

impact of climate change on coastal communities

• Property loss, damage, potential relocation: Coastal communities, especially poorer ones that can’t build up may need to relocate inland

  • Seawalls or other barriers can be built higher, but this just delays eventual flooding

• Loss of barrier islands: islands that buffer coastal communities/ecosystems from wind & waves may be lost as sea level rises

impact of climate change on atmospheric currents

• Widening & weakening of Hadley cell: as temperature difference between equator and poles decreases, air ascending and expanding from equator travels further before sinking

  • This shifts subtropical zones (dry, desert biomes) toward the poles and expands the tropics

  • Regions between 30⁰ and 60^o may experience drier climate as cool, dry, descending air from Hadley cell shifts north & south

• Weakened, destabilized Jet Stream: as arctic warms faster than other areas of earth, temperature difference between equator & poles weakens

  • Because temperature & pressure difference between polar & subtropical regions is what drives the polar jet stream, less difference between them means weaker, wobblier jet stream

    • Leads to extreme cold spells in eastern US & dry spells in western US

impact of climate change on marine ecosystems

• Altered range of marine ecosystems: some new marine habitats will be formed by rising sea level flooding coastline 

  • Some areas of ocean will become too deep to receive sunlight & photic zone will shift up, further from ocean floor

• Altered ranges for organisms: warm water holds less O₂, so many fish populations have declined, or migrated to cooler waters

impact of climate change on ocean circulation

• Suppression of thermohaline circulation: global ocean current that redistributes heat from the equator, salt, and nutrients by mixing ocean waters could slow or stop altogether

  • ice melt from Greenland → especially cold, freshwater buildup in north Atlantic

  • Freshwater is less dense than salt, preventing it from sinking

  • This cold north Atlantic slows warmer Gulf Stream waters, cooling Europe & slowing global thermohaline circulation

unequal global warming

polar regions of earth are warming faster than other regions (polar amplification)

• especially the arctic (N. pole) because there is more land & less water to absorb heat

  • melting sea ice = more expose ocean water, absorbs more sunlight than ice & snow, leading to more ice melting (P feedback loop)

• distribution of tropical heat to poles by thermohaline circulation also warms poles

• melting of permafrost

  • air pollution, adds soot/other PM to atm, distributed to poles by atm. circulation

    • darker, soot/PM covered in ice absorbs even more heat due to low albedo

impact of climate change on polar ecosystems

artic sea ice loss = habitat loss

• seals use it for resting & finding holes for breathing

• algae grow on ice, forming base of artic food web

• polar bears use ice for hunting seals at breathing holes

9.6

9.7

9.8

9.9

HIPPCO

• habitat fragmentation/loss

• invasive species

• population growth

• pollution (pollutants)

• climate change

• over-exploitation

habitat fragmentation/loss

Breaking of larger, continuous habitats into smaller, isolated patches; disrupts breeding, hunting, migration

• Deforestation/logging (lumber, cities, roads), Wetland draining (ag, urbanization), River water level decreased by dams

metapopulations

mostly isolated, subpopulations connected by habitat corridors; this can allow some gene flow (mating between populations) and improve genetic diversity 

invasive species

Invasives such as z. mussel and kudzu vine outcompete native species for food/space, lowering populations

population growth

Human pop. growth drives hab. loss, Urbanization, ag. expansion to feed more people remove/fragment hab.

pollution (pollutants)

Oil spills reduce marine org. pop. size, Pesticides (glyphosate, atrazine) kill non-target species

climate change

Shifts biomes & therefore species habitat ranges can change temp. & precip. patterns too rapidly for a species to adapt or migrate, causing pop. decline or extinction

sea level rise

precipitation change

• Warming global. temp. will decrease precipitation in some areas, leading to soil desiccation and desertification

  • Will increase in some areas, expanding tropical ecosystems

temp. change

• Warming temp. can shift biomes

  • Boreal forest & temperate coniferous forests may shift northward; tundra may decrease

over-exploitation

Excessive hunting or poaching (faster than reproductive rate) leads to pop. decline & potential extinction

edge effect

where two ecosystems such as forest-grassland or ocean-river (estuaries) meet have diff. characteristics than the middle of each ecosystem

• Some species thrive in the edge habitat & biodiversity is often higher in edge habitats due to diversity of food, shelter, and nutrient resources

• Edge habitats can expand range of potentially disruptive species (ex: brown headed cowbird) that thrive in grassland-forest edge

  • Brood parasite that leaves its eggs in the nests of songbirds for them to raise, unknowingly