Cold

The prolonged drought in the Sahel, beginning in the 1970's was driven by large-scale anthropogenic changes in the climate. Sulfate aerosol emissions in the Northern Hemisphere locally suppressed some of the warming driven by greenhouse gases. This caused the ITCZ to shift further south , which triggered the drought in the Sahel.

Northern south

Which one of the following choices about the loss of sea ice is TRUE?

Sea-ice loss contributes to increased rates of shoreline erosion

Which of the following statements accurately describes the connections between heat, air pollution, and human health?

Heatwaves are often associated with stagnant air, which means that the concentration of pollutants can build up in the air. These conditions lead to high concentrations of near-surface ozone and particulate matter.

Which of the following accurately describes how scientists predict rainfall will change in the future?

Heavy rainfall events will happen more often, and they will be more intense

The loss of ice from mountain glaciers is important when accounting for rates of global sea-level rise. Why is their contribution significant?

Mountain glaciers are sensitive to increases in temperature because, for the most part, they are already subject to melting temperatures for at least part of the year.

First, just focus on the range (difference) between the maximum winter and minimum summer extent. This range is larger in Region B . Now inspect when in the calendar year the sea-ice extent is at its maximum or minimum for each region. Based on this timing, you can infer that Region A is showing the Arctic sea-ice extent (so Region B must be showing the other pole).

Region B the Arctic

True or False? The special IPCC report that came out in 2018 stated that some regions have experienced increased flooding, but that this is not a clear global trend.

True

In 2011, a NASA satellite observed this large iceberg drifting in the Labrador Sea, off the east coast of Canada (the star on the map shows the location). Based on what you know about the cryosphere, you can surmise that this iceberg ....

Was created as a result of a calving event from a Greenland ice stream, then drifted further south

True or False: Wildfires are always associated with heatwaves and heatwaves always induce wildfires.

False

Which of the following does NOT accurately describe what scientists predict about future extreme heat? (in other words, which statement below is false)

In regions that will become more humid, we expect lower nighttime temperatures

The largest differences in seasonal rainfall can be observed in which region? (in other words, which region sees the biggest difference between the top and bottom panels?)

India and Bangladesh

Within the Hadley cell, air masses descend from the top of the troposphere toward the surface close to which latitude(s)?

The horse latitudes (30 degrees N/S)

A glacier is initially in equilibrium, so the total accumulation is equal to the total melt. The glacier would transition to a negative mass balance if ... snowfall rates decrease OR the rate of surface melt increases .

decrease increase

If sea ice melts, sea level...

does not change

True or False: According to the IPCC's most recent report, as global average temperatures rise, all regions that are currently dry will experience more humid heat waves.

false

Deforestation increases the risk of a flooding event.

increases

Mid-latitude rainy storm events are associated with regions of low pressure.

low

Find the icon referring to a heat wave in Texas (in the Southern US), and click on it (The title that pops up is "Exceptionally warm'" Texas summer, 2011. The study found that the likelihood of a summer temperature as extreme as the one in 2011 was ....

10 times greater due to anthropogenic emissions

Sea ice in the Arctic is vulnerable to global warming: projections indicate that end-of-summer sea ice may disappear by the middle of the century. Four options are listed below, two of which accurately describe why the Arctic's sea ice is vulnerable. Which ones? Increased areas of open water in the Arctic Ocean absorb more incoming shortwave radiation. The persistent ozone hole above the Arctic permits high-energy shortwave radiation to reach the surface, causing further warming. The reduced extent of summer sea ice means there is a smaller proportion of thicker, multi-year ice. The orientation of Earth's axis means that the Arctic is the location on our planet that is consistently closest to the Sun.

Increased areas of open water in the Arctic Ocean absorb more incoming shortwave radiation. The reduced extent of summer sea ice means there is a smaller proportion of thicker, multi-year ice.

During Part 2 of the lecture, I showed a map of flooding volume worldwide during El Niño vs La Niña years. Here, I am showing just a subset of that map--I have zoomed in on just the US and then, in yellow boxes, highlighted the Pacific Northwest of the US. We will spend a day discussing El Niño and La Niña during week 6. But even without further background knowledge, based on the maps, you can infer that the likelihood of a major flood event in the Pacific Northwest increases during La Niña years--these episodes tend to bring more rainfall to our region.

La Niña La Niña

Which of the following does NOT accurately describe what is leading to the increased loss of the Greenland ice sheet?

Most precipitation is now falling as rain, instead of snow

Greenland's total cumulative ice loss between 1992 and 2018 was greater than Antarctica's. Which of the following is a logical explanation for this?

The Antarctic has not experienced as much warming as the Arctic, particularly in East Antarctica, where the ice is relatively stable

A scientist sets up an attribution study to test if a particular heat wave was caused by climate change. Which of the following outcomes would give the scientist confidence that the heat wave may have been influenced by global warming?

The scientist ran computer modeling experiments under different climate scenarios (with and without anthropogenic greenhouse gases), and showed that the likelihood of the heat wave increased under an anthropogenic global warming scenario

Unsurprisingly, more arid conditions lead to greater burn areas. But this relationship is not linear! As aridity increases, the area burned increases [ Select ] ["at a higher rate (the slope of the line gets steeper as aridity increases)", "at a lower rate (the slope of the line gets less steep as aridity increases)"] The areas burned in Washington State between 1984 and 2020 are all either in the Cascade mountains or on the [ Select ] ["eastern", "western"] side of the Cascades. The graph on the right shows the probability of the fuel aridity value from climate models. In the future we expect it to be more arid than in 1991-2020. This is primarily because overall temperatures will be warmer. These warmer temperatures, in turn [ Select ] ["increase", "decrease"] the amount of water that is able to be evaporated from the surface.

at a higher rate (the slope of the line gets steeper as aridity increases) eastern increase

The loss of sea ice has impacts other than feedbacks in the climate system. As the extent of summer sea ice in the Arctic decreases we expect that... rates of (and damage from) shoreline erosion will increase . high-latitude shipping routes will become more available. the length of the seasons for polar bears to hunt will shorten . the depth of snow in nesting sites for ringed seals will be thicker (more abundant, deeper)

increase more shorten thinner (less abundant)

Overall, between 1893 and the end of their monitoring periods, all four glaciers lost mass. Therefore, you can infer that the total mass balance over this time period was [ Select ] ["positive", "in equilibrium", "negative"] . The blue shading denotes a time period, beginning in 1983 when most of the glaciers began to re-advance instead of continuing their retreat. This re-advancement can be explained by either a local [ Select ] ["warming", "cooling"] OR a(n) [ Select ] ["increase", "decrease"] in snowfall. (The paper finds that it was the temperature effect, which in turn was a function of anomalous wind patterns) The only glacier in this set that did NOT experience a re-advancement phase was the [ Select ] ["Stocking", "Tasman", "Fox", "Franz Josef"] .

negative cooling increase Tasman

In regions of surface convergence (where two air masses meet) and subsequent uplift we expect it to be ...

rainy

During the monsoon's rainy season, land surfaces are relatively warm compared to the ocean, and surface winds blow the air from the ocean to the land .

warm the ocean to the land

Most of the ocean is showing a warming trend since 1982. From the linear trend, you can calculate that the parts of the Arctic Ocean that have the strongest warming signal (e.g. the ocean just north of Iceland) have warmed by about 0.1 degrees C over this 40-year period. As the area of sea ice cover decreases, [ Select ] ["more", "less"] incoming solar radiation is reflected away. In turn, the warmer ocean is unable to support sea ice growth. This is a [ Select ] ["negative", "positive"] feedback loop.

.1 less positive

The model suggests that between 1981 and 2000, you could expect a 300 mm rainstorm event once every __________ or so.

100 years

The global mass change from mountain glaciers between 1961 and 2016 was -9625 Gt of ice. Every 362 Gt of ice loss is equivalent to 1 mm of global sea-level increase. So how much have mountain glaciers contributed to global sea level since 1961? Approximately....

27 mm

The Hintereisferner glacier retreated the most since observations began: it retreated by approximately2750 meters. This is outside of the range of its expected length variability. However, if the Hintereisferner glacier retreated only as much as either the Koryto or South Cascade glaciers , there would still be a small (but non-zero!) chance that Hintereisferner's retreat would still be within the range of variations driven by year-to-year variability in the climate.

2750 either the Koryto or South Cascade glaciers

A 2-degree increase in Celsius is equivalent to a _____ degree increase in Fahrenheit (think: temperature change)

3.6

The total surface area of the Greenland ice sheet is 1.7 million square kilometers. Look closely at the peak melt day of 2021 in late July (the tallest peak). Approximately 50 % of the ice sheet experienced some melt during that event!

50

Since the Antarctic is made up of a landmass surrounded by oceans, ocean currents naturally cause sea ice to drift away from the continent and melt in warm waters; little sea ice remains by the end of summer. However, the Arctic region is best described as an ocean surrounded by landmasses, so sea ice is less mobile. Some sea ice is, therefore, able to remain throughout the summer in the cold, high-latitude waters Therefore, we expect more multi-year ice to be present in the Arctic .

Antarctic Arctic Arctic

First look only at the average projections (the bold future lines). There is little difference between the median change under a high vs. low emissions scenario in [ Select ] ["Antarctica", "Greenland"] . If we follow the SSP5-8.5 trajectory, a high-emissions scenario, we expect [ Select ] ["Greenland", "Antarctica"] to contribute more to sea level rise by the end of the century. Now, look at the ranges (the shading). If we again follow the SSP5-8.5 trajectory, the worst-case scenario indicates that [ Select ] ["Greenland", "Antarctica"] will contribute the most to global sea-level rise. But, if we follow the SSP1-2.5 trajectory, the best-case scenario indicates that [ Select ] ["Greenland", "Antarctica"] could actually begin to regain mass, and would not contribute to global sea-level rise.

Antarctica Greenland Greenland Antarctica

Which of the following statements about Antarctica's ice loss is TRUE?

Antarctica loses mass primarily through calving.

This graph shows the cumulative melt day area in Greenland for 2020, 2019, 2018, and 2012, as well as the 1981-2010 median and typical ranges. The melt day area is the sum of the area melted each day between April 1st through November 1 Therefore, the cumulative melt day area adds each day's melt area to the previous total. This is why each line gets larger over timeFor example, if on April 1, 5000 km2 experienced melt, and on April 2, 7000 km2 experienced melt, then the value on this chart for April 2nd would be 5000 + 7000 = 12,000 km2 You can see that 2012 experienced the most extensive melt on record. This is the same year that Arctic sea ice experienced a significant amount of loss (think back to earlier this week). By the end of the 2020 melt season, the cumulative melt area was greater than the 1981-2010 median, but within the historical interquartile range.

Arctic sea ice greater

True or False: Heatwaves only occur in years when the global average temperature is high.

False

The city of Rochester, NY (located in upstate New York, latitude, 43oN, elevation 153 m above sea level) receives, on average, 2.5 meters of snowfall each year. Why don't glaciers cover the whole city?

Warm spring and summer temperatures melt away any snow that has fallen in the winter--in order to grow a glacier, some amount of snow needs to survive through the summer season.

Humidity is an important factor in extreme heat events. Which of the following accurately describes the role of humidity/water vapor? (In other words, which one of the following statements is true?)

Water vapor and clouds trap outgoing radiation, which means that temperatures can remain high on humid nights.

Imagine that someone makes the following statement: On Feb 14-15, 2021, Dallas, Texas reached -19˚ Fahrenheit, the city's coldest temperature since 1930 and second-coldest on record. This is evidence that global warming is not real. Which of the following options is the best way to refute this statement?

We expect to see large snowfall amounts and cold temperatures--even record-breaking levels -- in some places, even as the global average temperature increases. A single event does not prove or disprove that the climate is changing.

Mountain glaciers around the world have retreated and lost mass compared to 1976. To date, mountain glaciers in Western Canada and USA have, on average, lost the most mass compared to their 1976 values. If you were taking this class in 1995, which part of the world would have actually experienced mass gain (relative to 1976)? Scandinavia

Western Canada and USA Scandinavia

What is an ice shelf?

a permanent sheet of ice that floats on the water, but is attached to ice that is on land.

What is an ice stream?

a region of fast-flowing ice within an ice sheet, which moves a lot of the ice from the interior to the margins

The two panels show the average daily precipitation for two months of the year, January and July. Consider the seasonal movement of the Intertropical Convergence Zone (the ITCZ), and how this shifts the pattern of heavy precipitation north and south of the equator. With this in mind, you can deduce that the bottom panel is July (meaning the other one is January). (Hint: focus on differences between the panels in Africa, the Atlantic, N Australia, and India )

bottom

The figure above is modified for clarity from Bounoua et al. 2015, Environmental Research Letters. It shows the effect of the Urban Heat Island in three US metropolitan areas: Washington DC, Phoenix, and Kansas City. Summertime average hourly surface temperatures are shown for the urban areas (red lines), the surrounding rural areas (black lines), and for the most common vegetation in the surrounding rural areas (green lines). Local time on the x-axis begins at 1:00 AM and goes through to midnight (hour 23 = 11:00 PM) Use this figure to fill in the dropdowns. For DC, the greatest temperature difference between urban and nearby vegetated land occurs in the middle of the [ Select ] ["night", "day"] . At hour 13 (1:00 PM), which area experiences the smallest temperature difference between its urban and surrounding rural areas? [ Select ] ["Phoenix", "Kansas City", "Washington DC"] During the middle of the day which city is actually cooler than its surrounding vegetated environments? [ Select ] ["Washington DC", "Phoenix", "Kansas City"] Note: this occurs because introduced vegetation in the city like irrigated lawns and trees actually provides more cooling than the nearby natural vegetation! For all three areas, at what time of day is the urban area temperature most similar to the surrounding vegetated area?

day phoenix phoenix very early morning

Now we'll compare the historical time between the fires to the projections: Regardless of fire management strategies, in the future, we can expect that the time between fires will [ Select ] ["decrease", "increase"] (compared to the historical time between fires). Another way of saying this is that we expect fire FREQUENCY (how often fires occur) to [ Select ] ["increase", "decrease"] . Focus on the middle lines of the box plots--this is the median of the models, which we'll consider the most likely projection. In the future, we can expect that fire suppression strategies [ Select ] ["will not", "will"] make the years between fires longer. Why may this be the case? Let's look at the next figure!

decrease increase will

In the lecture, I noted that the expectation is that, for most regions of the world, future warming will look like a simple shift in the temperature distribution--the shape will not change. But some regions may experience a change in the shape of their temperature distributions. In this figure, the historical temperature distribution is displayed by a solid line, and the future temperature distribution is dashed. In this scenario, the variability and the symmetry of the distribution have both changed from the historical to the new climate. (Figure from Kristen Guirguis et al., Climate Dynamics 2018) The probability of hot days (shown in orange) is higher in the future climate. The probability of cooler days is higher in the historical climate.

future historical

Sailors have a saying "Cold is the night when the stars shine bright." A cloud-free night cools down faster because clouds...

have a greenhouse effect

Over the last decade (2010-2020), a reduced snowpack has led to declining streamflows in central-western Argentina. This, in turn, has reduced lake levels and groundwater storage. Taken as a whole, this is an example of a(n) _____ drought.

hydrological

The simplest expectation is that, in a warming world, the distribution of temperatures will simply shift toward warmer temperatures. (see the left figure above). An overall warmer climate will result in more hot summer days and fewer bitterly cold winter days. Dr. Joel Schwartz (from the Harvard School of Public Health) and his colleagues sought to understand how this shift in temperatures would lead to a shift in temperature-related mortality. Their work is summarized in the right figure above. In the future... there is a projected [ Select ] ["increase", "decrease"] in deaths due to warming in the summer months. there is a projected [ Select ] ["increase", "decrease"] in deaths due to warming in the winter months (since very cold temperatures will be less common). Overall there is expected to be a net [ Select ] ["decrease", "increase"] in deaths attributable to temperature.

increase decrease increase

The researchers sought to understand the effect of evaporation on local and global temperatures. The results of this study show the following: The process of evaporation leads to a(n) [ Select ] ["increase", "decrease"] in the presence of low clouds. Low clouds [ Select ] ["absorb", "reflect"] a lot of sunlight. Therefore, the evaporation of water leads to local cooling and global cooling .

increase reflect cooling cooling

The colors of the pins show whether human influence altered the likelihood or intensity of the heat event. The vast majority of the studies found that there is evidence of human influence on these extreme heat events.

is

Sweating is less effective in a humid environment because condensation cannot happen as readily.

less evaporation

As Dr. Caldeira mentions, local evaporative cooling might actually cause more warming on a broader scale. How could this be possible? Two of the following explanations are mentioned in the video and could explain this phenomenon. Evaporation increases the concentration of water vapor in the atmosphere. Because water vapor is a greenhouse gas, it absorbs and re-emits longwave radiation to the surface, increasing surface temperatures. The process of evaporation requires energy, so when the water vapor condenses again, this causes local heating where the condensation occurs in the atmosphere.

longwave heating

According to the IPCC's 2018 special report, there is low confidence in the significance of recent drought and dryness trends at the global scale. However, in terms of future drought, the 2021 IPCC AR6 report projects that when droughts occur in the future, they are likely to be more frequent and severe .

low more frequent and severe

Note that this question is worth 2 points The image below is modified for clarity from Gurguis et al. (Climate Dynamics, 2018). The graph shows the distribution of daily maximum summertime temperatures in Odessa, Texas. The distribution drawn with solid line shows historical observations, while the dashed line shows the same distribution, but shifted 4 degrees C warmer. The orange shading shows temperatures above the historical 95th percentile (heat waves), and the red shading indicates temperatures that have not yet been encountered in Odessa. For your reference: 30oC = 86oF; 40oC = 104oF Historically (solid line), the probability of experiencing "hot weather" is [ Select ] ["higher", "lower"] than in the warmer climate (the shifted distribution) Historically, Odessa has been [ Select ] ["more", "less"] likely to experience a daily maximum temperature of 30 degrees C than it would in a world that is 4 degrees warmer (shifted distribution) Historically, Odessa has been [ Select ] ["less", "more"] likely to experience a daily maximum temperature of 40 degrees C than it would in a world that is 4 degrees warmer (shifted distribution) Based on what you know about our city's climatology, Seattle's threshold for "hot weather" (days hotter than the 95th percentile) is [ Select ] ["more than/warmer", "less than/cooler"] than in Odessa, Texas.

lower more less less than/cooler

In the Arctic, sea ice reaches its maximum extent in March and its minimum extent in September .

march September

In 2020, Las Vegas went 240 consecutive days without rainfall. It rained on April 19, 2020, and no measurable precipitation fell again until December 17, 2020. (The previous record was 150 days in 1959) This kind of measurement describes a(n) ....

meteorological drought

It is lush on the west side of the Cascade Mountains and drier on the east side. This precipitation pattern is driven by...

midlatitude storm systems and the orographic rain shadow effect

By the end of the century (2081-2100), the models project that a 300 mm rain event will happen more frequently than in the recent past (1981-2000).

more

The image below comes from NASA's Earth Observatory and shows a false-color image of Providence, Rhode Island on July 31, 2002. The map data was acquired from NASA's Landsat 7 satellite and shows the temperature, ranging from dark purples (cooler temperatures) to bright yellows (hotter temperatures). Based on what you know about urban heat islands, you can surmise that the areas in purple have more vegetation (compared to the areas in yellow).

more

In the short term, more droughts likely mean more fires, because vegetation will be dried out. However, if the drought is intense and long-lived (megadrought conditions), we may expect a(n) decrease in fires. This is because a prolonged drought leads to conditions where landscape cannot support plant growth.

more decrease

Snowfall rates over New Zealand's Franz Josef glacier (pictured below) are increasing; so is the rate of melt. Is the glacier going to grow or retreat (compared to today)?

not tell from the information provided

The graph displays the minimum annual extent of Arctic sea ice, from 1985 to 2020. The thickness of each color represents how much of the total extent was made up of ice of a particular age. The total height of the line (all of the colors stacked on top of one another) represents the total minimum sea ice extent in a given year. In 1985 most (>50%) of the total extent of the ice was [ Select ] ["younger", "older"] than 3 years old. As of 2020, most (>50%) of the remaining ice was [ Select ] ["older", "younger"] than 2 years old.

older younger

The ice-albedo feedback is a negative feedback. So as the Arctic warms in response to recent climate change, this feedback mechanism serves to amplify the warming.

positive amplify

A heat wave occurs in a dry climate. This dries out the moisture that was in the soil. As the soil moisture dries, more of the incoming solar energy goes to heating the land's surface (rather than evaporation). Therefore, the surface will get warmer during the daytime.

positive feedback

When an air mass that contains water vapor meets a mountain it is forced to rise. The water vapor condenses, leading to rainy conditions on the windward side of a mountain. This describes orographic lift .

rainy orographic lift

During heat waves, the air often becomes stagnant, trapping pollution. Which of the following choices does NOT accurately describe why pollution worsens heat effects on human health?

sulfate aerosol concentrations increase, absorbing more incoming shortwave radiation

As scientists predict climate change out to the end of the century, uncertainty in global average temperature projections primarily stem from the rate and the total amount of anthropogenic greenhouse gas emissions and...

the climate's sensitivity to changes in radiative forcings

According to a 2013 research paper ... Despite their adverse impacts, definitions and measurements of heatwaves are ambiguous and inconsistent... (Perkins and Alexander, Journal of Climate) According to your textbook and the lecture, the best definition of a heatwave is based on....

the number of days that are among the hottest in that month's long-term record (e.g. the past few days have been among the hottest 5% of days in the past two decades!)

The figure above comes from the US Center for Disease Control and shows the number of emergency department visits for heat-related illness for the states in the Health and Human Services Region 10: Alaska, Idaho, Oregon, and Washington. Spend some time interpreting this figure to select the appropriate dropdowns: In May and June of 2019, emergency department visits related to heat illness were mostly in the rest of the United States . In May and early June of 2021, emergency department visits related to heat illness were mostly in Alaska, Idaho, Oregon and Washington . In the last week of June of 2021, emergency department visits related to heat illness were mostly in Alaska, Idaho, Oregon and Washington .

the rest of the United States Alaska, Idaho, Oregon and Washington

Early in 2020, during the Antarctic summer, Casey Research Station (shown on the map above) and the nearby Windmill Islands experienced their first recorded heatwave. For three days, the maximum temperatures were all above 7.5°C, and on January 24, a temperature of 9.2°C was recorded. This value is almost 7°C above the station's 30-year mean for the month of January. Scientists who are studying this stretch of warm days designated it a heatwave because... only one option below makes sense

these temperatures are among the hottest recorded for this area, which could cause stress for organisms that have adapted to live there.

The figure above comes from the 2018 Nature paper that I showed in the lecture slides--mass change in Antarctic ice between 1992 and 2017. The uncertainty of one standard deviation is shown by the shading around the bold lines. In the lecture, we focused on the cumulative loss over the continent, and how this loss was mostly from West Antarctica. Now, look at the mass change in East Antarctica. Cumulatively, the East Antarctic Ice Sheet has contributed very little/not at all to sea level rise over this time period. the cumulative contribution of each area over the whole time period is the value at the end of the time series--so the 2017 value. The uncertainty in terms of mass change in East Antarctica is larger than the uncertainty in the mass change in West Antarctica.uncertainty is shown by the width of the shading around the bold lines.

very little/not at all larger than