chapter 11 Flashcards
Climate change science
the interdisciplinary study of the causes and consequences of changing climate for all Earth systems and the sustainability of human societies
@ Paleoclimatology
the science that studies the climates, and the causes of variations in climate, of past ages, throughout historic and geologic time
Proxy methods
information about past environments that represents changes in climate, such as isotope analysis or tree ring dating; also called a climate proxy
@ Past climate
paleoclimatology, using proxy indicators (ice-core date, sediments, coral reefs, ancient pollen, tree-ring)
@ Current climate
weather station data, remote sensing data, numerical modelling using General Circulation Models (GCM)
@ Future climate
numerical prediction using GCMs
Isotope analysis
a technique for long-term climatic reconstruction that uses the atomic structure of chemical elements, specifically the relative amounts of their isotopes, to identify the chemical composition of past oceans and ice masses
« light » oxygen, 16O
evaporated more easily but condenses less easily
« heavy » oxygen, 18O
evaporated less easily but condenses more easily
Oxygen Isotope Analysis
Since 16O evaporates more easily, over time the atmosphere becomes relatively rich in « light » oxygen. As this water vapour moves toward the poles, enrichment with 16O continues, and eventually this water vapour condensed and falls to the ground as snow, accumulating in glaciers and ice sheets. At the same time, the oceans becomes relatively rich in 18O partly as a result of 16O evaporation at a greater rate and partly from 18O condensing and precipitating at a greater rate once it enters the atmosphere
@ how scientists can determine the isotope ratio of seawater at the time the shells were formed
by extracting a core of these ocean-floor sediments and comparing the ratio of oxygen isotopes in the CaCO3 shells
- shells with a high 18O/16O ratio were formed during cold periods; this with low ratios were formed during warm periods
explain how can we defined layers based on horizons of dust and volcanic ash that landed on the ice surface and mark specific time periods
- Lower 18O/16O ration (less « heavy » oxygen in the ice) suggest colder climates, where more 18O is tied up in the oceans and more light oxygen is locked into glaciers and ice sheets
- Higher 18O/16O ratio (more « heavy » oxygen in the ice) indicates a warmer climate during which more 18O evaporates and precipitates onto ice-sheet surface
@ causes of the dissociation of large gas hydrate deposits - breakdown of the solids into liquids and gases
can destabilize seafloor sediments, causing a loss of structural support that can lead to subsidence and collapse in the form of submarine landslides
- hydrate deposits; wherever methane occurs in the presence of water under elevated pressures and at relatively low temperatures
Carbon Isotope Analysis
scientist can use the carbon isotope ration of dead plant material to determine past vegetation assemblages and their associated rainfall and temperature conditions
Radioactive isotope
an unstable isotope that decays, or breaks down, into a different element, emitting radiation in the process. The unstable isotope carbon-14 has a constant rate of decay know as a half-life that can be used to date plant material in a technique called radiocarbon dating
@ Lake Cores
The sediments at the bottom of glacial lakes provide a record of climate change extending back as far as 50 000 years
@ Tree Rings
Wider rings suggest favourable growth conditions, and narrower rings suggest harsher conditions or stress to the tree (often related to moisture or temperature)
@ Dendroclimatology
the study of past climates using tree rings. The dating of tree rings by analysis and comparison of ring widths and colouration is dendrochronology
Speleothem
a calcium carbonate mineral deposit in a cave or cavern, such as a stalactite or stalagmite, that forms as water drips or seeps from rock and subsequently evaporated, leaving behind a residue of calcium carbonate that builds up over time
Stalactites
grow downward from a cave roof
Stalagmites
grow upward from the cave floor
Limestone
is a sedimentary rock that is easily dissolved by water. Natural chemical processes at work on limestone surfaces often form caves and underground rivers, producing a landscape of karst topography. Within caves and caverns
The rate of growth of speleothems depends on several environmental factors
- amount of rainwater percolating through the rocks that form the cave
- Water acidity
- Water temperature
- Caves humidity conditions
Corals
- Corals are marine invertebrates with a body called a polyp that extracts calcium carbonate from seawater and then excretes it to form a calcium carbonate exoskeleton. These skeletons accumulate over time in warm, tropical oceans, forming coral reefs
- During the last glacial maximum and the Younger Dryas, temperature rise occurring about 14 000 years ago and again about 12 000 years ago at the end of the Younger Dryas
- X-rays of core samples extracted from coral reefs reveal seasonal growth bands similar to those of trees, yielding information as to the water chemistry at the time the exoskeletons were formed
Earth’s Short-Term Climate History
- The last glacial period lasted from about 110 000 years ago to about 11 700 years ago, and the abrupt warming marked the end of the Pleistocene Epoch
- the capacity of cold air to absorb water vapour is less than for warm air, resulting in decreased snowfall during glacial periods
- Greenland ice cores: past 20 000 years of temperature and snow accumulation
variation in the earth’s elliptical orbit around the sun
earth’s elliptical orbit about the sun, known as eccentricity, is not constant and changes in cycles over several time scales. The most prominent is a 100 000 year cycle in which the shape of the ellipse varie by more than 17.7 million km, from a shape that is nearly circular to one that is more elliptical
Milankovitch cycles
the consistent orbital cycles - based on the irregularities in Earth’s orbit around the Sun, its rotation on its axis, and its axial tilt - that relate to climatic patterns and may be an important cause of glacials and interglacials. Milutin Milankovitch (1879-1958), a Serbian in insolation that affected temperatures on Earth
variation in the earth’s axial title
Earths axial title, at present about 23.5°, varies from 21.5° to 24.5° during a 41 000 year period
Continental Position and Topography
the position of the continents also impacts ocean currents, which are critical for redistributing heat throughout the world’s oceans
The movement of continental plates causes episodes of mountain building and spreading of the seafloor
what is the primary natural source of CO2 emissions in the atmosphere
outgassing from Earth’s interior through volcanoes and vents in the ocean floor
what happen when theres an accumulations of aerosols ejected into the stratosphere
can create a layer of particulates that increases albedo so that more insolation is reflected and less solar energy reaches Earth’s surface, like a volcanic eruption
Climate feedbacks
a process that either amplifies or reduces a climate trend toward either warming or cooling
Carbon sinks
an area in Earth’s atmosphere, hydrosphere, lithosphere, or biosphere where carbon is stored; also called a carbon reservoir
Global carbon budget
the exchange of carbon between sources and sinks in Earth’s atmosphere, hydrosphere, lithosphere, and biosphere
how can the ocean dissolves CO2 in seawater
by biological processes through photosynthesis in microscopic marine organisms called phytoplankton
how does ocean acidification happen
dissolved CO2 mixes with seawater, carbonic acid (H2CO3) forms
what is the most abundant natural greenhouse gas in the Earth
water vapour
explain the positive feedback of water vapour in the atmospheric system of earth
As air temperature rises, evaporation increases, because the capacity to absorb water vapour is greater for warm air than for cooler air, As atmospheric water vapour increases, higher rates of condensation will lead to more cloud formation, and thin clouds can cause warming, and then more evaporation happen
explain the carbon positive feedback
Rising atmospheric CO2 leads to increased plant growth and microbial activity, and eventually leads to a greater amount of carbon emitted to the atmosphere rather than stored in the ground
- initial warming leads to increases in gas concentrations; elevated gas concentrations then amplify warming, and so on
explain the CO2 positive feedback
the subsequent increase in precipitation and enhancement of chemical increase in precipitation and enhancement of chemical weathering then acts to buffer warming by removing CO2 from the atmosphere and transferring it to the oceans
- which create acid water, can chemically break down rocks, affected marine sediments and corals
@ what pourcentage of the ice sheet’s surface was melting, in Greenland
97%
@ how much of Arctic permafrost will thaw over the next 200 years, if not sooner
between one and two thirds
@ sea ice
sea ice is composed of frozen seawater, which forms over the ocean, it helps to cool the planet by reflecting sunlight
problems with sea ice
summer sea ice may disappear sooner than predicted by most models; some scientists estimate an ice-free summer Arctic Ocean within the next few decades
Scientists think that the decline of multiyear ice causes an overall thinning of the Arctic pack ice that this becomes vulnerable for further, accelerating melt
Sea-Level Rise
Sea level is rising more quickly than predicted by most climate models, and the rate appears to be accelerating
From 1993 to 2013, satellite data show that sea level rose 3.16mm per year
what causes sea-level rise
roughly two-thirds of the rise comes from the melting of land ice in the form of glaciers and ice sheets
The other third comes from the thermal expansion of seawater that occurs as oceans absorb heat from the atmosphere and expand in volume
what can cause a greater amount of water vapour in the atmosphere
affects weather in a number of ways and can lead to « extreme » events involving temperature, precipitation, and storm intensity
carbon dioxide
- Principale greenhouse gas produced by human activities
- Come from the combustion of fossil fuels, biomass burning, removal of forest, industrial agriculture, cement production
- A residence time of 50 to 200 years in the atmosphere, but can take tens of thousand of years if it goes in the marine sediments
methane
- Second most prevalent greenhouse gas produced by human activities
- Concentration are ncrease faster than CO2
- Residence time of about 12 years in the atmosphere
- 25 times more effective at trapping atmospheric heat than CO2
- 72 times more effective than CO2
- Two-thirds of the total methane in the air is anthropogenic caused
- Mining of coal, oil, and natural gas, processes in flooded fields associated with rice cultivation
nitrous oxide
- third most important greenhouse gas produced by human activity
- A lifetime in the atmosphere of about 120 years
- Fertilizer in agriculture, wastewater management, fossil fuel burning, some industrial practices
halogenated gases
- Produced only by human activities; fluorine, chlorine, bromine
- Are ozone-depleting substances
- The most important of these are chlorofluorocarbons
Radiative forcing
the amount by which some perturbation causes Earth’s energy balance to deviate from zero; a positive forcing indicates a warming condition, a negative forcing indicates cooling; also called climate forcing
@ General circulation model (GCM)
complex, computer-based model that produces generalizations of reality and forecasts of future weather and climate conditions. Complex GCMs (three-dimensional models) are in use in the United States and in other countries
@ Atmosphere-Ocean General Circulation Model (AOGCM)
a sophisticated general circulation model that couples atmosphere and ocean submodes to simulate the effects of linkages between specific climate components over different time frames and at various scales
consequenses of sea-leavel getting higher
higher water levels, higher tides, and higher storm surges to many regions, particularly impacting river deltas, lowland coastal farming valleys, and low-lying mainland areas, national and international migration
what is the paris agreement
in 2016, 195 countries signed to keep the increase in global mean temperature in the 21st century to less than 2 Celsius degrees above pre-industrial levels, as well as strengthening the ability of countries to respond to the impacts of climate change
what to be careful of when taking a position on climate change
Media misinformation often comes from corporate interests whose financial gains are at stake if climate change solutions are imposed
Growing number of blogs and other social media that often present results not yet evaluated by other scientists
no regrets movement
Taking action on climate change must focus on lowering atmospheric CO2, societies have little to lose and much to gain by employing these strategies
how to save the planet from climate change
Not only as individuals, but also as an international community
