Midterm

For an Earth climate sensitivity of 0.8°C/W/m2, what radiative forcing would be required to cool the Earth's surface temperature by 2°C?

-2.5

What was the single largest contributor to human CO2 emissions 1) prior to 1900 and 2) after 2000?

1) Land-use change, 2) Coal

Place the following carbon reservoirs in the Earth system in order from the reservoir that has the MOST carbon (1) to the reservoir that has the LEAST carbon (4).

1. Sediment and rock 2.deep ocean 3. land 4.atmosphere

Water with the ------isotope is more easily evaporated, while water with the ------isotope is more easily precipitated. This results in land ice that has a ----- 18O/16O ratio than seawater. With this water stored away in land ice, the seawater 18O/16O becomes ------

160 180 lower higher

The modern rate of CO2 input to the atmosphere from volcanoes is 0.05 Gt C/year, while the rate of CO2 input from humans is approximately _____ than this rate.

200x

The graph below shows how the 18O/16O ratio of the calcium carbonate shells of foraminifera changed from 65 million years ago to the present. Based on this record, when was Earth's climate the warmest? Note: look carefully at the y-axis!

50 million years ago, when the 18O/16O ratio was the lowest

Below are three graphs of climate change (labeled A, B and C) which cover different time spans. In each case, the right side shows data from the present. Match the starting time (i.e., the left side labeled "Past") of each graph to the appropriate time in the past.

A = AD 300 B = 450 thousands years ago C = 11.5 thousand years ago

Consider the following feedback diagram, and suppose sunlight intensity were to change due to some outside factor. Where would this forcing connect to the feedback diagram most directly? A Would this connection be positive or negative? n

A, positive

The image below shows a photograph of sediments from the Paleocene-Eocene Thermal Maximum (PETM). The y-axis shows depth below the seafloor (meters of core depth, mcd). The youngest sediments in the core image are located at the top of the y-axis, while the oldest sediments are at the bottom of the y-axis. The blue line on the right side shows the amount of calcium carbonate in the core sediments at each depth, with more calcium carbonate to the right. The sediments deposited during the warmest times are between 335 mcd and 336 mcd . During that time period, there was a sharp decrease in calcium carbonate burial. This change in calcium carbonate burial worked to lower atmospheric carbon dioxide, helping to return atmospheric carbon dioxide levels to their pre-PETM values.

Answer 1:between 335 mcd and 336 mcd Answer 2:decrease Answer 3:lower

he top graph below shows a curve of hypothetical human carbon emissions. Recall that 10 Pg C emitted into the atmosphere would result in an increase of 5 ppm in the atmospheric concentration of carbon dioxide, assuming all of the emitted carbon remains in the atmosphere. In the bottom plot, which curve would best describe the resulting concentration of carbon dioxide through time, assuming that all of the carbon emissions remains in the atmosphere? Note that curves C and D have the same value from 2030 to 2040.

B

Consider the following bathtub diagram. Suppose A represents the input to the atmosphere of carbon dioxide from burning fossil fuels by humans, and B represents the total amount (or concentration) of carbon dioxide in the atmosphere. Which of the following is true? Choose all that apply.

B is increasing. C includes output to the surface ocean through dissolving carbon dioxide gas in the water. C includes output to the land through carbon fertilization and forest regrowth.

Of the following, which two gases contribute the most to the absorption of the infrared radiation leaving the Earth surface at low latitudes? Choose two gases below.

CO2, H2O

Which of the following is true of carbon dioxide concentrations, as measured in the atmosphere since the 1960s? Choose all that apply.

Carbon dioxide varies seasonally, with highest values during the winter (as experienced by each hemisphere) and lowest values in the summer (again, as experienced by each hemisphere). The average carbon dioxide concentrations have been increasing year-to-year.

Which of the following is not a line of evidence showing that the observed atmospheric CO2 rise is mostly due to fossil fuel burning?

Contemporaneous increase in atmospheric radiocarbon (14C) concentration

Which of the following best explains why the temperature of the Earth's surface rises when the concentration of greenhouse gases increase?

Earth must emit more radiation in order to balance the energy received from the Sun, so Earth's temperature must rise

The rate of increase in mean annual global air temperature has been constant since 1850.

False

The rise in China's per capita carbon dioxide emissions since ~2002, shown in the graph below, can be explained by population growth.

False

As noted in class, we can rule out heat transport and heat storage as the causes of rising air temperatures. Which of the following is the best explanation for why?

For both heat transport and heat storage to cause warming, there would need to be corresponding cooling somewhere in the Earth system. However, we do not observe such cooling.

Which of the following best describes Holocene climate conditions?

Generally stable climate, with weak cooling in the last 5,000 years

For the feedback diagram in the previous question, suppose sunlight intensity were to increase. After ~1 million years, long enough for the feedback to fully occur, what would happen to the temperature relative to the temperature just before the increase in sunlight intensity? It would be the same. What would happen to the CO2 concentration relative to the concentration just before the increase in sunlight intensity? It would be the same.

It would be the same. It would be lower.

which, if any, of the following climate change events in Earth's history is carbon dioxide NOT thought to have played an important role? Choose all that apply.

Little Ice Age

Of the following, which two gases are the most abundant gases in the atmosphere? Choose two gases below.

N2, O2

Which of the following indicates that Earth is warming because of changes to the atmosphere? Choose all that apply.

Ocean temperatures show that warming has occurred in all ocean basins, with the greatest warming near the ocean surface. Glaciers and ice sheets are melting, contributing water to the oceans and thereby raising sea level. Boreholes in bedrock show that the ground has been warming from the surface downward.

Which of the following is true about the relationship between global temperature change and human inputs of CO2? Select all that apply.

Past global temperatures were strongly correlated with cumulative total human CO2 emissions, and are expected to continue to be highly correlated through 2050, regardless of the emission scenario.

Of the following, which best describes the "Faint Young Sun Problem"?

The Sun was much fainter than today for much of Earth's history. If the ancient atmosphere were similar to today, we would expect that there would not have been liquid water until ~1.5 billion years ago because temperatures would have been too cold. Instead, we have evidence of liquid water for almost all of Earth's history.

What is the likely cause of climate change since about 50 million years ago?

The collision of India with Asia created the Himalayan mountain range and Tibetan Plateau, increasing the "weatherability" of rocks in the region.

In lecture, we discussed the fact that ocean sediments are an important source of climate-proxy data, which are useful in reconstructing past climate. What makes ocean sediments so important?

The deep seafloor provides a quiet environment where sediments accumulate with few interruptions, preserving fossils and chemical traces of climate conditions.

In the sequence of events associated with a Snowball Earth glaciation, an initial cooling set off two main feedback cycles: ice/albedo and CO2/weathering. Which one of the following best describes what happened?

The ice/albedo feedback was more rapid, causing complete glaciation. The CO2/weathering feedback eventually caught up and returned climate to its original state.

Ocean acidification is a lowering of ocean pH due to higher CO2concentrations in the water. True/False: During the Paleocene-Eocene Thermal Maximum (PETM), a sudden increase in carbon dioxide in the atmosphere led to ocean acidification, making it much less likely for fossils of organisms that make their shells out of CaCO3 to be preserved in ocean sediments from that time.

True

Go to the website http://climatemodels.uchicago.edu/geocarb/Links to an external site.and use the GEOCARB model to determine how plants impact weathering, and hence climate. To do this, change the "Transition CO2 Spike" to 0 and change the "Plants" dropdown menu under the "Spinup" column to "no" (this will begin the model with no plants, and plants will immediately be added at the start of the simulation). See the image below for guidance. Once you have selected these parameters, scroll to the bottom of the page and choose "Show 1 million years".

Weathering increases with the addition of land plants, causing global climate to cool over hundreds of thousands of years.

Which of the following chemical equations shows the process by which carbon is removed from the atmosphere and added to the land reservoir of organic carbon?

Which of the following chemical equations shows the process by which carbon is removed from the atmosphere and added to the land reservoir of organic carbon?

The long-term rise in instrumental CO2 records is due to

an excess of organic carbon oxidation relative to organic carbon production land use changes ("deforestation") burning of fossil fuels (all of the above)

Earth's climate has largely ----- over the last 50 million years. This led to the growth of ice sheets in ----- around 35 million years ago, and the growth of cyclic ice sheets in the ------ around 3 million years ago.

cooled Antarctica Northern Hemisphere

During the Last Glacial Maximum (~20,000 years ago), temperatures were ---- in the Northern Hemisphere and ---- in the Southern Hemisphere relative to today's temperatures.

cooler cooler

A requirement for a molecule to function as a greenhouse gas is that it ________ .

has the ability to be asymmetric

The primary role of volcanoes in Earth's temperature on timescales of 1-10 years is

increasing sulfate aerosols in the stratosphere, thereby causing temperatures to decrease.

The primary role of volcanoes in Earth's temperature on timescales of greater than 1 million years is

increasing the greenhouse gas concentration in the atmosphere through emitting carbon dioxide, thereby causing temperatures to increase.

Choose all that apply. The addition of sulfate aerosols to Earth's atmosphere:

leads to greater scattering of incoming solar radiation sources from explosive volcanic eruptions and fossil fuel burning increases Earth's albedo through direct and indirect effects

A negative radiative forcing results when the amount of energy entering the Earth system is greater than the energy leaving the Earth system through the top of the atmosphere.What would be the radiative forcing associated with a 1.5 degree C decrease in temperature for a system with a climate sensitivity of 3 degree C/W/m2? [ Select ] W/m2

less than -0.5

Climate records indicate that, compared to interglacial times, during the glacial periods that occurred over the last eight hundred thousand (800,000) years: - CO2 concentrations were ---- - the amount of global forest cover was ---- - Northern Hemisphere ice volume was ---- - and sea level was -----

lower lower higher lower

Which of the following was NOT a feature of Earth's climate at the peak of the last ice age?

ncreased forest cover in northern North America

Match the following paleoclimate proxy archives with the time span that their records can cover.

ocean sediments -- 100 mil years ago today ice cores -- 1 mil years ago today instruments--150 years

Which of the following components of the Earth system has taken up the greatest amount of energy since 1955?

oceans

The processes of erosion and weathering mainly occur ----- , and sedimentation mainly occurs ----- .

on land in the ocean

An example of the dynamic in Question 1 from Earth's history is ----------------- An example of the dynamic in Question 2 from Earth's history is the ----------

the "Year Without a Summer," following the eruption of Mount Tambora in 1815. the processes that allowed Earth to "escape" Snowball Earth conditions.