Global Warming test #3 UTA-1330

What are isotopes?

Variations of the same element with a different number of neutrons, which leads to a different mass

What is isotope fractionation?

The heavier isotopes will remain in the liquid phase more often than the lighter isotopes

Isotope fractionation: Oxygen during evaporation

- H2O is fractionated during evaporation

- Depletion varies with temperature in the atmosphere.

- There is less 18O in the atmosphere as it gets colder.

Isotope fractionation: Carbon in marine organism shells

- 12C and 13C are stable 14C is radioactive

- 12C is fractionated into living tissue

- Ocean water is enriched in 13C

- Carbonate shells reflect changing 12C/13C of seawater

What can oxygen isotopes in ice or in marine shells tell us about the Paleotemperature?

- Oxygen isotopes can be used as paleotemperature proxies

- Coral calcite can be used for isotope studies (paleotemperature reconstruction)

What do tree rings indicate?

- Annual layers

- Ring width is related to environmental conditions (rainfall, temperature, and fires)

What does coral growth indicate?

- Annual layers and seasonal patterns

- Rings are indicators of environmental changes

What are speleothems and how can they be used in paleoclimate research?

- Cave deposits such as stalactites and stalagmites

- Can be used as temperature proxies (oxygen isotopes) or rainfall indicators (layer thickness)

What are Ice cores?

Annual snow layers turn into ice

Ice core: Resolution

Annual to centennial resolution

Ice core: Range

Up to ~800,000 years

Ice core: What can be measured?

- Precipitation can be estimated from layer thickness

- Temperature can be inferred from oxygen isotopes

- CO2 is measured from trapped air

- Dust is measure of wind velocity and direction and local erosion

What is the difference between ice cores and sediment?

Ice cores stretch back over 800,000 years into the past

Sediment cores have been used to look up to 200 million years into the past

How do cores archive paleoclimate information?

Isotopic changes in pelagic or benthic fossils as proxies of paleotemperature and productivity

How old is the Earth?

4.543 billion years

What are some indicators of glaciation ("icehouse world")?

- U-shaped valleys

- Hanging valleys

- Horns

- Cirques

- Tillites identify periods of glaciation, clarify the extent of glaciation, and contain rock fragments that indicate the place where the ice sheets originated

How do coal, organic-rich clays and petroleum form?

Formed from organic residue of plants and animals

What do these deposits mean in terms of carbon distribution in the Earth system?

- Carbon sequestration

- Coal deposits acts as major carbon sink and lower the level of CO2

What are alluvial fans?

Fan-shaped mass of alluvium deposited as the flow of a river decreases in velocity.

How can alluvial fans be used as climate indicators?

Often evidence of tectonic activity and resulting enhanced erosion

What are limestone and chalk?

- Made of calcite (CaCO3)

- Forms in warm water

- Carbon sequestration

- Chalk is limestone from phytoplankton shells

What are indicators of deserts/dry conditions?

Precipitation, temperature, streamflow, ground and reservoir water levels, soil moisture, and snowpack.

What are indicators of ancient dunes?

- Large crossbedding

- Infer wind direction

What are indicators of evaporites?

- Occur in areas of intense evaporation (mostly in subtropical arid zones)

- Dissolved materials start to precipitate out of the solution

What are laterite and bauxite as tropical soil indicators?

- Iron and aluminum-enriched soils

- Form in hot and wet tropical climates by weathering

What is the relationship between volcanic activity and climate?

- Causes short-term cooling due to the aerosols

- Causes long-term warming if there is a sustained release of CO2

Sedimentary structures: What do ripple marks indicate?

Moving water

Sedimentary structures: What do desiccation cracks (mud cracks) indicate?

- Drying sediment

- Evidence of shallow water

- Evidence of evaporation

Fossil leaves: what is the temperature (shape)

Leaf margins are used to estimate paleotemperature (cold=toothed, warm=smooth)

Fossil leaves: Atmospheric CO2 (stomata)

Stomatal density is used to estimate CO2 concentration in the atmosphere

How can pollen in sediments be used?

Pollen is widely dispersed, indicating changes in vegetation

When did the Permian end?

252 million years ago

End-Permian: What was the climate like?

Transition into hothouse climate

End-Permian: What did probably cause the rise of atmospheric CO2?

- CO2 released by volcanism

- Carbon (CH4) released from coal beds into the atmosphere

End-Permian: Eruption of Siberian Trap Basalts; what happened in/to the ocean?

CO2 release - rapid global warming - acid rains - rapid enhancement of continental weathering - enhanced continental weathering - delivered excessive nutrients to the oceans - lead to marine eutrophication, anoxia, acidification, and ecological perturbation

End-Permian: How severe was the extinction?

- 70% of terrestrial vertebrates extinct

- 90% of marine species extinct

End-Permian: Which toxic gas may have been emitted by the oceans?

Methane

End-Cretaceous: what was sea level like?

Extremely high sea levels

End-Cretaceous: When did the Cretaceous end?

66 million years ago

End-Cretaceous: What happened during the Oceanic Anoxic Events?

- Many areas with coal formation

- Intense volcanism

End-Cretaceous: What was the likely trigger of the end-Cretaceous extinction?

Major meteorite impact

Paleocene-Eocene Thermal Maximum (PETM): when did it happen?

About 56 million years ago

Paleocene-Eocene Thermal Maximum (PETM): Which greenhouse gas additions happened?

- Spikes in CO2

- Temperature spikes (about 5 - 8°C global warming)

- Ocean acidification

Paleocene-Eocene Thermal Maximum (PETM): What were the likely sources?

- Release of methane from methane hydrates

- Release of methane from coal deposits baked by magma

Cooling trend since about 50 million years: potential causes?

- Sea level falling

- Temperature falling

- CO2 falling

- Mountains rising

- Ice sheets growing

- Sea-floor spreading slowing down

Cooling trend since about 50 million years: Why/how does mountain building lead to global cooling?

Mountains rising

First big ice sheets in the Miocene?

- 23 million years old

- Ice growth in antarctica and greenland

- Proto-Antarctic Circumpolar Current (opening of the Drake Passage)

How did the opening of the Drake Passage, the opening of the Fram Strait, and the closing of the Isthmus of Panama likely affect Earth's climate?

- 13-12 million years ago opening of the Fram Strait, leading to water exchange between Arctic and Atlantic Ocean

- About 5 million years ago, the closure of the Isthmus of Panama, increased heat transport to high latitudes in the North Atlantic.

- IT HEATED THE EARTH's CLIMATE

Quaternary Period: Pleistocene and Holocene Epochs (start/end times?)

- Pleistocene: 2.58 million years ago to 11.7 thousand years ago

- Holocene: 11.7 thousand years ago to today

Quaternary Period: What are orbital cycles?

Changes in eccentricity, obliquity, precession, direct climate change

Quaternary Period: How do orbital cycles correlate with Pleistocene glacials/interglacials?

The three Milankovitch Cycles impact the seasonality and location of solar energy around the Earth, thus impacting contrasts between the seasons.

Pleistocene atmospheric CO2 and temperature (as derived from ice cores)?

- CO2 enhances glacial cycle

- Warm cycle: carbon released from the oceans

- Cool cycle: carbon absorbed by oceans

What are pleistocene sea level changes?

Sea level was about 100-130 meters lower than it is today during glacial stage

Younger Dryas event (when and what?)

- About 14,500 years ago

- Earth's climate began to shift from a cold glacial world to a warmer interglacial state

What is the "Medieval Warm Period"?

9th to 13th century

What is the "Little Ice Age"?

16th to 19th century

What is the Hockey Stick curve?

Temperature changes linked to solar intensity and volcanism

Climate Models: What is a typical grid resolution?

Up to ~2° is currently a typical resolution, and 20-30 layers in the atmosphere and ocean

Climate Models: How are Earth system processes represented?

Fundamental laws of physics are applied to solve budget equations for each earth system component

Climate Models: What kinds of boundary conditions are needed?

Solar radiation, greenhouse gas concentrations, orbital parameters; topography and bathymetry

Climate Models: How are model results evaluated?

Evaluation by comparing output to observations

- Horizontal grid: latitude-longitude

- Vertical grid: height or pressure

Correlation coefficients for surface air temperature, emitted terrestrial radiation, precipitation, shortwave cloud radiative effect

What does IPCC stand for?

Intergovernmental Panel on Climate Change

For what time range are model predictions made in the IPCC report?

Results depicted for near-term (2021-2040), mid-term (2041-2060), and long-term (2081-2100) relative to 1850-1900 Scenarios start in 2015

What does SSP (in the IPCC Report) stand for?

Shared Socioeconomic Pathway

What do the numbers in the SSP indicate?

Radiative forcing

What is the approximate range of temperature predictions by the end of this century for the different scenarios?

1.5°C - 4°C

What is the general pattern for precipitation predictions?

Global surface temperature increase will continue until at least the mid-century under all emission scenarios considered

What is the prediction for the change in carbon uptake by land and ocean?

38% - 70%

What is the range of predictions for the change in sea ice coverage?

Sea ice coverage is going to decrease

What is the range of predictions for the change in ocean surface pH?

The ocean surface pH can either increase or decrease

What is the range of predictions for the change in sea level?

The ocean sea level is predicted to increase

Which areas in the US have so far seen the biggest changes in hot extremes, heavy precipitation, and drought, respectively?

Western states of California and Nevada

How are vegetation biomes expected to shift in a warmer climate?

- Vegetation models predict poleward shifts of biomes.

- Plants increase water use efficiency in higher CO2 world

- Overall greening, but also increase in respiration

How will species living at high latitudes or high altitudes likely be affected in a warmer climate?

Species that live in high latitudes or high altitudes might

become replaced by species moving in from lower latitudes/elevations

How is the occurrence of wildfires likely to change in a warmer climate?

Change in wildfire probability for high-emission scenarios (due to hotter and drier summers as well as vegetation shifts)

What is coral bleaching?

Rising water temperature leads to bleaching when colored symbiotic zooxanthellae are expelled from the coral polyps