SPU29MidtermReview
How has temperature changed over the last century?
0.8-1C
Evidence for: The Paleocene-Eocene Thermal Maximum likely caused by a release of carbon dioxide to the ocean or atmosphere from the oxidation of approximately 5000 GT of Organic Carbon
1) Oxygen isotope records from deep-sea sediments 2) Carbon Isotope records from deep-sea sediments
Evidence for: The earth is warmer now than it has been for at least the last thousand years
1) Tropical Ice Cores and Tropical Ice Sheet Retreat
How long will it take for weathering reactions to remove all the CO2 released from burning fossil fuels?
100,000 years
What was the sea level during the Eocene relative to today and what accounted for the difference?
100m higher than today because of thermal expansion and no ice during the eocene
What was the temperature of the deep ocean during the Eocene?
12C
current rate of sea level rise: 1900-1993 by tide gauges
2.4mm/year
current sea level rise: 1993-current by satellite altimetry (TOPEX)
3.5mm/year
What is the current CO2 level in the atmosphere?
400 ppm
present co2 levels
400ppm
Rahmstorf sea level rise by 2100
40cm-1m using paleoclimate and what has been observed
What was the CO2 Level during the Eocene
500ppm-1500 ppm
When did the PETM happen
55Ma
When did the Eocene occur?
55Ma to 34 Ma
How would you describe the temperature of the deep ocean during the PETM?
6C of deep ocean warming on top of the 12 degrees we saw during the Eocene (for a max reach of 18C)
What distinguishes the ice cores Lonnie Thompson collects from other cores?
A clear, high resolution, annual signal
Over the past 1000 years, global temperature records from proxy and instrumental records show
A slow cooling trend over the last 1000 years, followed by a sharp rise over the last 100 years
The big driver of increases in emissions is
AFFLUENCE
The Paleocene-Eocene Thermal Maximum (PETM) was characterized by
An abrupt increase in temperatures followed by a slow decrease
The stabilization wedges
Are a way to help think about the amount of emission we must avoid to stabilize CO2 levels AND Must continue to grow past 2054 to stabilize atmospheric CO2 AND Help illustrate how different technologies can grow to displace CO2 emissions
Epicontential seaways
Are shallow seaways that extend to central areas in continents AND Often occur during periods of high sea level AND Are nutrient rich and a viable place to bury large amounts of organic carbon
5,000 Gton of net carbon emissions would be possible if
Both We uses all the fossil fuel reserves and We use most of the fossil fuel reserves and climate feedbacks react to release more CO2
What is the main difference between atmospheric CO2 during the Eocene and presently due to anthropogenic emissions?
Changes in CO2 and temperature occurred much slower during the Eocene, allowing the climate to adjust slowly. The changes happening today are much faster, and it is a question of how quickly adaptation can take place.
In addition to a temperature signal, the cores also show
Changes in atmospheric composition from events like the implementation of legislation to remove lead from gasoline
The changes in CO2 concentrations over the past 800,000 years were caused by _______ and the changes over the past 70,000,000 years were caused by ______.
Changes in the partitioning of CO2 between the ocean and atmosphere; Chemical weathering
Is the current climate relatively warm or cold compared to the climate over the past 70 million years?
Cold
We can determine how different causes are contributing to sea level rise by
Comparing satellite observations to the patterns of sea level rise predicted for ice melt from particular ice sheets and glaciers and thermal expansion from observed temperature changes
Currently δ 13C in the atmosphere is
Decreasing due to the burning of fossil fuels depleted in 13C
When ice floating on the ocean melts, sea level _____
Does not change
True of False: Measuring sea level change at one location gives you global sea level change
FALSE
True of false: most hurricanes make landfall
FALSE
True or False: As long as technology improves to decrease the emissions per GDP, global emissions of greenhouse gases will decrease
FALSE
True or False: The green revolution solved the problem of overpopulation
FALSE
True or false: There is no evidence that the rate of ice melt in Greenland and Antarctica is accelerating
FALSE
True or False: If the earth were ever in a snowball earth configuration, it would be permanently stuck there. The climate would be too stable to ever melt the ice sheets.
False
True or False: the PETM resulted in mass extinctions
False
True or false: There is no longer methane hydrates in the ocean today
False
In order to stabilize CO2 levels in the atmosphere, we need to
Get to essentially 0 emissions
Evidence for: the loss of ice from Greenland ice sheet is accelerating over the past decade
Grace(gravity field) or TOPEX (satellite altimetry)
Climate change may affect a storm like Sandy through
Higher sea surface temperatures causing more intense storms AND Changes in the high pressure system causing more storms to turn westward and make landfall
Over the past 15 years, the rate of sea level rise appears to have _____ as compared to tide gauges over the last century.
INCREASED
The possibility of the Ross Ice Shelf breaking up is concerning because
It allows for the rapid flow of ice from Antarctica into the ocean
It is possible that a smaller event triggered a sequence of feedbacks, releasing a lot of soil carbon release. If this were the case, why is this concerning?
It could indicate that burning fossil fuels could put in place a series of positive feedbacks that release more and more carbon.
How does the rate of chemical weathering change with temperature and precipitation rate?
It increases with increasing temperature and increasing precipitation
If the current rate of sea level rise from Greenland melting would only result in 5 cm of sea level rise over the next century, why are we concerned?
It is possible that the rate ice melt could accelerate, contributing to much more sea level rise
Why do we care about the PETM?
It provides an analogue for what we are doing today with fossil fuels
If the weathering rate of rocks increased, how would the rate of burial of organic matter change?
It would increase
Tide gauge reconstructions of global sea level rise are
Less accurate than satellite measurements of sea level rise because local differences in sea level rise need to be accounted for
If a large portion of the ice mass on Antarctica melted instantaneously, globally sea level would rise. Locally, we would expect to see
Less sea level rise near Antarctica due to a decrease in the gravitational attraction from the loss of ice mass
The density of stomata (holes that allow plants to take in CO2 and release water) on plants has been used to determine CO2 concentrations in that atmosphere. In an atmosphere with higher CO2would you expect plants to have a higher or lower stomata density?
Lower
Evidence for: The Carbon Dioxide concentration in the atmosphere has never been much above 300 parts per million for at least 400,000 years
Measurements of gas bubbles from the Vostok Ice Core
All of the following contribute to global sea level change except : Thermal expansion of ocean water Melting Ice Sheets Melting Icebergs Changes in groundwater pumped out of the earth and into rivers and streams
Melting Icebergs
The Tethys Ocean had ___ calcium carbonate compared to the Pacific Ocean, leading to ____ volcanic emissions of CO2 during the Eocene
More; greater
The power dissipation index includes all of the following except Wind speed Number of storms that make landfall Duration How large they are
Number of storms that make landfall
Argo
Ocean measurements of temperature from floats in the ocean
Evidence for: During the PETM, temp rose approximately 6degreesC
Oxygen Isotope Records from deep sea sediments
delta13C in sediment cores
PETM, what causes change? mass release of carbon, we think
Paul Ehrlich and John Holdren suggested that different environmental impacts can be driven by
Population AND Economic Growth AND Changes in Technology
The IPCC's emission scenarios are
Possible emissions that might occur based on different cases of how the world's fossil fuel use may change
GRACE
Satellite that measure gravitational field and gives us information about ice melt
To explain the decrease in δ 13C during the PETM, large releases of isotopically depleted carbon from a variety of sources have been suggested, such as volcanic eruptions, methane hydrate destabilization, and organic carbon release. Why do some sources require greater quantities of carbon release to explain the δ 13C excursion?
Some sources are more depleted in 13C, and hence require less carbon release to explain the decease of 2.5‰ in the isotopic record
Comparing individual climate proxies for temperatures (i.e. tree rings, lake sediments, and ice cores) there is
Strong agreement regarding slow cooling with a sharp warming after the mid 1800s
True or false: We can predict the local distribution of sea level rise caused by the melting of different ice sheets
TRUE
If volcanic emissions increased, what would prevent CO2 from building up in the atmosphere?
Temperatures would warm and precipitation would increase, leading to an enhance rate of chemical weathering that would eventually balance volcanic emissions
How long will the impact of CO2 emissions from fossil fuels be felt?
Tens of thousands of years
If the sun is responsible for the current warming, that suggests
That the climate is extremely sensitive to small changes in radiative forcing, and when aerosols can no longer cancel out the impacts of greenhouse gases, we will see significant climate changes
The IPCC predictions for sea level rise over the next century differ from those made by Stefan Rahmstorf. These differences are best explained by
The IPCC assumes current rates of ice melt will continue, while Rahmstorf assumes the past relationship between global temperature and sea level will hold in the future
How would you explain the change in δ13C during the PETM?
The PETM dropped 2.5 to 3 per mil
The PETM stands out in the oxygen isotope record as well as
The carbon isotope record AND The calcium carbonate content of the sediment
Why doesn't a large volcanic eruption explain the PETM?
The carbon released during a volcanic eruption is only slightly depleted in 13C requiring such a large increase in oceanic and atmospheric CO2 that ocean pH would also change. This change in ocean pH would alter the partitioning of 13C between the ocean and atmosphere, making it such that you could never decrease the ocean's isotopic composition by 2.5‰ from a volcanic carbon source.
Peak temperatures over the next few centuries will be determined by
The cumulative emissions of CO2 to the atmosphere
Why didn't Paul Ehrlich's predicted population bomb actually occur?
The development of nitrogen fertilizer AND Dwarf wheat and the development of high productivity crops AND There is still a chance it will occur in the future
Hurricane Katrina caused so much destruction in New Orleans because
The dike and levees were damaged and the city flooded
There have been periods in earth's history where the climate was substantially warmer than today. If we have examples of periods where the climate was naturally warmer, why are increasing temperatures from anthropogenic emissions a concern?
The earth was substantially different at those times, with sea levels much higher and tropical plants and animals much further north than we would ever see them today
We can tell how quickly Greenland is losing mass by measuring
The gravitational field over Greenland
How does the release of methane fail to explain the temperature signal of the PETM?
The methane released would explain the initial spike in temperatures, but as it has a short lifetime, would quickly be converted to atmospheric CO2. In this case, the temperatures would quickly drop, as the levels of CO2 would not be large enough to cause the slow decrease in temperatures seen in the record.
It wasn't until around 34 million years ago that we see large variability of temperature in the foraminifera record. What is the source of this variability?
The onset of ice sheets amplified the feedback of temperature to changes in orbital configurations.
If volcanoes are constantly releasing CO2, why aren't these emissions as important as anthropogenic emissions?
The rate of emissions from volcanoes is about 100 times smaller than from the rate caused by burning fossil fuels.
The slow cooling of earth since the Eocene can be explained by
The switch from subduction of the calcium carbonate rich Tethys Ocean to the calcium carbonate poor Pacific Ocean and resulting decrease in volcanic emissions of CO2
If tectonic activity closed an epicontential seaway, we would expect
The water to evaporate, and the subsequent oxidization the organic rich muds, releasing carbon to the atmosphere
Why do we need additional proxies to determine CO2 levels during the Eocene, that we didn't need during the past 800,000 years?
There were no ice sheets at that time, so you can't determine the record from ice cores
If the ocean didn't take up any CO2, how would the long tail of carbon in the atmosphere be different?
There would not be a sharp dip in CO¬2 concentrations following the peak concentration
Lonnie Thompson demonstrated that the recent warming is not part of natural cycle through his work on
Tropical Ice Sheets
True of false - if we wait long enough, eventually CO2 emissions from anthropogenic activities will precipitate as calcium carbonate from weathering reactions.
True
True of false - over long time scales, weathering rates balance rates of volcanic outgassing?
True
Why would carbon dioxide levels increase in the atmosphere during a snowball earth configuration?
Volcanic activity would continue, but weathering would be suppressed
If the amount of calcium carbonate subducted increases, how would volcanic emissions of CO2 change?
Volcanic emissions would increase
Just after a snowball earth configuration melts, you would expect the climate to be
Warmer than present with a lot of CO2
What could push more species toward extinctions during present day climate changes that weren't relevant during the PETM?
We are currently in a glacial period, with more species living in cold environments than during the PETM which occurred when the earth was already in a warm state AND Human land use changes are already stressing biodiversity and threatening species survival AND The PETM occurred over 10,000 years allowing for species to adapt, while today the changes are occurring over a few centuries
When is the Ross Ice Shelf predicted to break off?
We don't know when it will break off
Over very long timescales as the sun continues to increase in luminosity, how will levels of atmospheric CO2 change?
We would expect them to decrease due to the silicate weathering thermostat
Huge drop in CaCo3 during the PETM was caused by
a huge ocean acidification event
Cooling timescale during the PETM
cooling occurred over 100,000 years because of weathering, but we don't entirely know why it warmed fast over 10k years first. We think it is because of organic carbon.
Evidence for: the world could escape from a snowball earth glaciation if the concentration of co2 in the atmosphere rose to very high levels of roughly 100,000 ppm
coupled ocean-atmosphere climate models
ice rafted debris
dansgaard oschgard events,, rapid melt on greenland
Tide guages
local differences in sea level change
co2 proxies and examples why they matter for Paleocene and eocene
phytoplankton, boron, stomata, matter because there was no ice during Paleocene/Eocene to extract data from ice cores
TOPEX
satellite altimetry, net sea surface changes in height
IPCC sea level prediciton for 2100
sea level will rise 20-40cm (using climate models)
delta18O in sediment cores
temperature
corals
temperature signals, carbonate signals
Evidence for: approximately 20 percent of the carbon emitted from fossil fuel combustion is currently being taken up by the terrestrial biosphere, approximately 20 percent by ocean
the measurements Keeling Curve of atmospheric CO2 from oxygen Mauna Loa, Hawaii, and Ralph Keeling's
LAKE DEPOSITS
used to make the hockey stick
Temperature change timescale during the PETM
warming over 10,000 years
