CU2_HW_STUDENT_Fall2023
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Geography
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Apr 3, 2024
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1 Name _________________ Homework Questions for Climate and Us Week 2
Due the week of December 4 1. Past and Present Climate The Antarctic ice sheet, which is about 3 km thick, has yielded ice cores that provide a paleoclimate record extending back to as far as 800,000 years ago. Figure 1 below shows temperature estimates and atmospheric CO
2
data from a 400,000 year-long record from Vostok in East Antarctica. CO
2
data are derived from direct measurement of ancient air bubbles trapped in the ice and temperature data are derived from a proxy: the isotope ratios of frozen water molecules. Figure 1.
Ice core paleoclimate data for the past 400,000 years from Vostok, Antarctica. a) Variations in temperature (degrees Celsius) vs. time (present day is at 0, age increases to the right). b) Variations in atmospheric CO
2
(ppm) on the same timescale. From Petit J. R. et al. (1999)
1
1
Petit, J.R., Jouzel, J., Raynaud, D., Barkov, N.I., Barnola, J.M., Basile, I., Bender, M., Chappelaz, J., Davis, M., Delaygue, G., and Delmotte, M. 1999. Climate and atmospheric history of the past 420,000 years from the Vostok ice core, Antarctica. Nature, 399(6735), pp. 429-436.
2 A. Over the past three million years, Earth has swung between mild (warm) climate periods and cold ones during which much of the northern hemisphere was covered in glacial ice. From the temperature record in Figure 1a, we can see that there have been four complete ice age cycles in the last 400,000 years, each lasting ~100,000 years on average with somewhat shorter variations superimposed. What is thought to be responsible for these cycles? What are the time periods of these cycles?
B. Study the Vostok records shown in Figure 1. (i)
Describe the relationship between temperature (Figure 1a) and CO
2
concentration (Figure 1b).
(ii)
What mechanism(s) might explain this relationship?
C. The planet Venus has a much higher atmospheric concentration of greenhouse gases. Most dramatic among them is CO
2
, which constitutes 96% of Venus’s
atmosphere, as opposed to Earth’s current ~0.04%. Using your knowledge of greenhouse gases in Earth’s atmosphere,
which of the following statements is/are CORRECT? Select all that apply. a.
Earth would not be at a habitable temperature without greenhouse gases, but the far higher concentration of greenhouse gases in Venus’ atmosphere is one of the reasons that Venus is uninhabitable.
b.
Greenhouse gases play a major role in amplifying temperature via negative feedback loops in the climate system of Venus and Earth. c.
Greenhouse gases such as CO
2
, CH
4
, and water vapor in the atmosphere absorb and re-
radiate longwave energy emitted by Venus back towards Venus, just like on Earth. d.
All of the above. Explain the answer(s) you chose in 1-2 sentences: Obliquity
41,000
yrs
Eisentricity
100,000
yrs
Precession
26,000
yrs
when
CO2
is
intreased
temperature
also
increases
greenhouse
gases
102
is
one
causes
heat
to
be
trapped
on
earth's
surface
0
we
need
some
greenhouses
gases
to
achieve
our
goldilocks
temperature
This
effect
happens
on
Venus
but
it
is
much
hotter
3 D. Ice, which covers 10 percent of Earth’s surface, is disappearing rapidly. NASA’s Global Ice Viewer shows how climate change has affected glaciers, sea ice, and continental ice sheets worldwide. (i)
Visit the Global Ice Viewer, and select ‘Glaciers’. Click on ‘About Glaciers’ on the bottom right to learn more. Choose one of the locations on the world map. Describe the location you chose, and what the images show. Make sure to indicate the amount of time that has passed between images. (ii) At the top, switch to ‘Arctic’. Click on ‘About Arctic Sea Ice’ on the bottom right
to learn more. Describe the trend in Annual Arctic Sea Ice from 1979 to 2022. What explains the intra-annual variation in sea ice area?
(iii) At the top, switch to ‘Greenland and Iceland’. Click on ‘About Greenland’s Ice Sheet’ on the bottom right to learn more. Of the three types of ice you have explored (glaciers, sea ice, and continental ice sheets), which will contribute to sea level rising by melting? Which will contribute to global temperature rise?
Explain your answer in 1-2 sentences. (iv)
As discussed in lecture, the predictability of future climate is complicated by feedbacks between different components of the climate system. In the space below, draw a feedback loop related to the melting of one of the forms of ice from the previous question.
(v) Is the loop you drew above an example of a positive or negative feedback loop? Explain in 1 –
2 sentences.
Alaska
Range
In
the
span
of
96
years
the
terrain
changes
from
snowy
and
icy
to
one
w
more
water
and
green
forestry
overall
negative
trend
in
arctic
sea
ice
in
this
time
frame
The
ite
is
melting
The
intra
annual
variation
in
sea
ice
are
is
due
to
the
ice
melting
in
summer
and
refreening
in
summer
glaciers
will
ion
tribute
to
sea
levels
rising
sea
ice
will
raise
global
temps because
it
helps
regulate
global
climate
through
sunlight
reflection
fossil
me
to
regulate
more
gh
gas
melts
ice
changes
global
climate
positive
because
the
more
we
change
the
climate
the
more
energy
we
need
It
can be
regati
e
if
we
change
our
sources
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4 E.
The CO
2
concentrations in Figure 1 are based on direct measurements from air bubbles in ice cores. What are two other methods that climate scientists use to study the past climate? For each method, identify i) what the method measures, and ii) how these measurements can be used to make inferences about past climatic conditions. 2. Predicting Future Climate Climate models are important tools that enable scientsists to predict future climates and its impacts. Models can be used to predict future CO2 emissions, temperature, precipitation, sea level rise, etc. In lecture, we focused on models that predicted different possibilities for global fossil fuel emissions that vary based on different emissions scenarios, as well as warming projections. Based on these models the Intergovernmental Panel on Climate Change (IPCC) predicted an increase in temperature of 3.7°C (relative to temperature between 1850-1900 CE) by 2100 according to the RCP 8.5 model (the “business as usual”
model). Comparing model outputs based on different emission scenarios allows us to assess the potential uncertainty or variability in future climate. Figure 2. Projected changes in mean global surface temperature under four emissions pathways The observed mean global temperatures are shown in black, while the ensemble model means for tree
rings
written
historical
records
people
wrote
down
1
0
0,6
rain
patterns
i
humidity
and
temp
plant
blooming
of
past
climates
patterns
can
teach
us
about
previous
climate
5 the global mean temperatures under pathways RCP8.5 (red), RCP6.0 (orange), RCP4.5 (light blue), and RCP2.6 (dark blue) are shown over the twenty- first century. The ensemble model spreads for the end of the century are represented by the vertical bars on the right (colored to match the corresponding RCP time series). Temperatures are relative to the 1986
–
2005 average. A.
Figure 2 is featured in this week's reading, and shows temperature increases predicted by an "ensemble" of different climate models. What do the different colored lines represent? What could contribute to the spread in model predictions as shown on the right-hand-side of the figure?
B. We can visualize these models using an interactive tool created by DKRZ, a laboratory for climate researchers working with climate models. Access the tool here: https://webvis.dkrz.de/ . You can explore different outcomes under models RCP2.6, RCP4.5, and RCP8.5, using the toolbar on the bottom right to move through time.
Set ‘
Climate Variable
’
to Mean Temperature Change over Time, and change ‘
Layout
’
to RCPs in Comparison.
(
i) Navigate to North America on the map. In what year do each of the RCPs reach above 3°C projected warming? (ii)
Navigate to the Arctic on the map. In what year do each of the RCPs reach above 3°C projected warming? (iii) Navigate to northern Africa on the map. In what year do each of the RCPs reach above 3°C projected warming? (iv)
Based on your observations (above), what area of the Earth will be impacted first by a changing climate? What does this suggest about global versus regional impacts of climate change?
In
all
RIPs
NorthAmerica
does
not
reach
3
oct
in
snorant
times
but
projected
2030
Around
2015
Afria
has
and
will
never
The
auctis
will
have
effects
first
This
means
that
global
warms
affect
diff
regions
at
different
paces
6 C.
Based on what you learned about climate models this week, what might lead RCP 2.6 to be closer to what will actually happen in comparison to RCP 8.5? N
ame three examples.
3. Reflections
A.
As you have seen in the different units of Frontiers of Science, converging evidence plays an important role in how scientists provide support for their hypotheses.
Describe how converging evidence relates to climate change using specific examples you learned about in this unit. B.
What methods of communication do you think might be most effective when speaking about climate change with someone who considers themselves a denier? C. Based on your expected major and career after Columbia, in what ways do you think you might be able to help address climate change and its consequences in the future? 1
used
renewable
resources
2
reduce
deforestation
3
Stop
using
fossil
fuels
climate
patterns
from
treerings
measuring
air
bubles
in
ice
and
written
records
it
all
points
to
the
earth
getting
warmer
Leave
them
in
a
burning
hot
building
so
they
can
know
what
it
feels
like
By
making
laws
that
prioritize
the
climate
future
of
developing
countries
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