GLOBAL WARMING
Cloud Feedbacks
- Low clouds tend to reflect more incoming sunlight; if warming causes lower clouds this leads to a negative feedback - High clouds tend to have a strong greenhouse effect; if warming causes more high clouds, this leads to a positive feedback
Water vapor (AKA humidity)
- The primary greenhouse gas: 60% of natural greenhouse effect - A feedback not a forcing
Attribution Studies...
-can help determine (in a probabilistic way) whether human-induced climate change increased the likelihood of a heatwave (or flood, drought, etc.) -Run climate models under scenarios with and without anthropogenic greenhouse gases, and calculate the probability of an event happening.
agricultural drought
-deficient in soil moisture -links characteristics of meteorological or hydrological drought to agricultural impacts -plant water demand -timing within the growth cycle of a crop -nearly 1.3 billion people rely on agriculture as their main source of income -severe droughts can lead to socioeconomic problems, famine and migration -drought affects places where hydropower provides a lot of electricity
hydrological drought
-deficit in water availability in lakes, reservoirs, snowpack, underground -often defined on a watershed scale -often lags behind meterological drought (but not always: can have one without the other)
meterological drought
-deficit precipitation -degree of dryness (as compared to some avg. amount) and the duration of the dry period -region specific
The world is predicted to warm much more over the next 100 years
-depends on how much we emit -and uncertainty in climate feedbacks
Can you explain why it is 342 W/m2 as a global average, but there are variations in space?
?
TRUE OR FALSE? Heatwaves only occur in years when the global average temperature is high.
False
According to a 2006 paper in the scientific journal Climate Dynamics (Jones, Sparks, and Valdes), the albedo of ash varies, but is, on average, approximately 0.5. Using this information, and the images above, did the albedo of the island increase or decrease after the volcanic eruption?
INCREASE
The gases that make up most of the atmosphere (nitrogen, oxygen, argon) are ---- greenhouse gases
NOT
The climate warms, so people choose to wear white t-shirts instead of black sweaters. This, in turn, slightly changes the albedo of the Earth's surface, reflecting away more incoming solar radiation. The climate then cools, because less sunlight is being absorbed, so people start to wear their black sweaters again.
Negative Feedback
The ____ wavelength of the Sun's radiation is in the Visible portion of the EM spectrum.
Peak
How does a volcanic eruption affect the climate in the short-term?
Strong cooling influence (our best guess is around -0.8 W/m2)
Shortwave Forcings (EXAMPLES)
Sulfate Aerosols -Most important shortwave forcing (from air pollution) -Direct effect of reflective aerosols: reflecting shortwave radiation away (Volcanoes are also a source of sulfate aerosols) Black carbon aerosols -small particles that absorb incoming solar radiation (have a low albedo) - aren't as abundant as sulfate aerosols Changes in the strength of the Sun (Solar variability is relatively small (0.2 W/m2 peak to peak) (Correlated with the sunspot cycle) Land cover changes -Negative forcing in total (clearing low-albedo forests leads to more reflection) Soot on Snow -positive forcing
The correct ranking for the following portions of the EM spectrum in terms of frequency, from higher to lower frequency.
UV, visible, infared
Weather V. Climate
Weather: varies from one day to the next Climate: average of the weather over a long period of time
Greenhouse gases ____
absorb and re-emit outgoing terrestrial longwave radiation.
A positive forcing results in...
warming of the climate
Monsoons: over certain land surfaces in the summer. The land warms/cools more quickly than the ocean. Can you explain some reasons why?
when you put more heat into the climate system, land should warm more quickly than oceans. This is because land has a smaller "heat capacity" than water, which means it needs less heat to raise its temperature.
CFCs (Chlorofluorocarbons: ozone depleting gases) and HFCs (replacements for CFCs)
- 12% of anthropogenic greenhouse effect - CFC concentrations are decreasing (due to recognition of ozone hole problem and Montreal Protocol) - Some HFCs are strong greenhouse gases though (their emissions are increasing, but are being somewhat curtailed by the Kigali agreement)
Carbon Dioxide (CO2)
- 26% of natural greenhouse effect - 64% of anthropogenic greenhouse effect (we emit a lot of it!) - Long-lived: average lifetime is 100 years, some remains in atmosphere for over 1000 years Does atmospheric lifetime make sense?
Urban Heat Island Effect
- Caused by heat from combustion, low-albedo surfaces, buildings keeping longwave radiation in, less vegetation for evaporative cooling - Within urban areas, temperatures can change over small distances—a function of vegetation and paved surfaces.
Nitrous Oxide (N2O)
- Global warming potential: ~300 - 6% of anthropogenic greenhouse effect - Anthropogenic emissions come from agriculture, chemical industry, deforestation
Ozone (O3)
- Greenhouse gas that is formed through interactions between anthropogenic sources (industrial/automobile emissions) + sunlight - Also a pollutant near the surface (troposphere) - Blocks harmful incoming UV radiation in the stratosphere
To detect climate change
- Have to look at averages and long-term patterns to detect a trend -Often short-term hot or cold extremes in the mid-latitudes are caused by movements of the jet stream -In the US, very hot days have become more common, as have hot nights
Methane (CH4)
- Shorter-lived (8 yrs) but a more potent greenhouse gas - Global warming potential: 25 - 17% of anthropogenic greenhouse effect - Produced naturally in wetlands; anthropogenic changes due to farm animals, landfills, natural gas leakage, rice
How is the incoming energy allocated?
-20% absorbed by atmosphere -50% absorbed at the surface -30% reflected back to space
Total Emissions (facts)
-Humans emit 36 gigatonnes of CO2 (10 Gt of carbon) each year into the 3200 gigatonne atmospheric reservoir of CO2 -Big players are China, USA, E.U. -Large population countries are higher on this list
Humidity (water vapor)
-Makes it feel hotter b/c evaporation is less effective (heat index measures this) -The greenhouse effect of water vapor also keeps nights warmer (which is particularly bad for human health)
C02 Facts
-a greenhouse gas, greenhouse gases warm the planet -Co2 concentrations have increased rapidly (from 280 ppm to over 400 ppm & rising, Values over last 400,000 years: 180-280 ppm, Recent increase is human-caused (90% fossil fuels, 10% deforestation)
Water vapor feedback:
-a positive feedback -warmer air can hold more water vapor (a greenhouse gas)
ice-albedo feedback
-a positive feedback -Ice/snow melts with increased temperature. Lowers albedo. What would happen if the temperature cooled? (negative feedback)
The Earth has warmed around ? C over the last 130 years
1 degrees C
False Statements (2)
1.) The ozone hole is caused by global warming 2.) Global warming is caused by the ozone hole
As scientists predict climate change out to the end of the century, uncertainty primarily stems from....
1.) the rate and total amount of anthropogenic greenhouse gas emissions 2.) the climate's sensitivity to changes in radiative forcings
Δ T = λ Δ F If the change in temperature is 6 oC and the change in radiative forcing is 4 W/m2 what is the value for the climate sensitivity parameter (lambda) in oC/(W/m2)?
1.5
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
World capita average=
4.8 tonnes CO2/yr
A 9 degree increase in Fahrenheit is equivalent to a _____ degree increase in Celsius (think: temperature change)
5
Can you read and interpret the "Keeling Curve"? (Atmospheric CO2 at Mauna Loa, Hawaii)
?
Total forcings (longwave + shortwave) since 1750: 2.3 W/m2 Why is this # less than the longwave forcings?
?
temp change
A 1 degree change in C =1.8 change in F
Flooding (FACTS)
Affected by many factors in addition to just extreme rain events -No clear evidence that the frequency or magnitude of floods is currently going up Hurricane Harvey—attribution study showed that the odds of a Harvey-like event have increased because of warming Floods (and droughts) will be among the most important impacts of global warming: hard to predict - Rare events - Limited data/observations - Land used changes
albedo
Albedo measures what fraction is reflected back -Varies from 0 to 1, black = low albedo, white = high albedo -Clouds, snow/ice important for increasing the albedo of Earth
Future of Extreme Heat
Basic expectation: shifting the distribution of temperatures towards hotter everywhere - More likely hot extremes, less likely cold extremes Many places will experience an increase in heat index (higher water vapor concentrations) -More greenhouse gases mean hotter nights in locations that don't dry out Some land areas are expected to dry out though -These will experience more intense dry heat (especially in the daytime)
The greenhouse gas(es) that has led to most of the anthropogenic longwave radiative forcing since 1750 is....
Carbon Dioxide
Per capita emissions—do you know how the number for per-capita emissions is calculated?
Carbon emissions per capita are measured as the total amount of carbon dioxide emitted by the country as a consequence of all relevant human (production and consumption) activities, divided by the population of the country.
___ climates tend to have a large diurnal (day-to-night) temperature range.
DRY
Drought (facts)
Defined as meteorological, hydrological, or agricultural -Effects of droughts on people and ecosystems: California and the Sahel -Increased risk of wildfire, crop loss, energy shortages Like floods, there are not enough direct observations to suggest high confidence in observed trends globally -But there is medium-to-high confidence for attribution of some specific droughts, and a general expectation that droughts will be more intense in the future
Long wave radiation (infrared light)
Earth COOLS by emitting longwave radiation out to space (lower energy than the sun; everything emits radiation, but warmer things emit more and at higher energy) - Greenhouse gases stop longwave radiation from escaping directly to space - They instead absorb, and re-emit longwave radiation in all directions - This means that more energy is trapped near Earth's surface, and that the Earth is warmer than it would be without greenhouse gases (GHG make the Earth habitable).
True or False: There is sufficient data to show that, for the past several decades, all land surfaces have experienced an increase in precipitation intensity.
FALSE
What is "good" vs "bad" ozone ?
Good Ozone: stratosphere Bad Ozone: troposphere
Extreme heat effects
Human health -Can suffer from direct effects (heat stroke), or associated effects (pollutionà lung/heart problems) -Length of heatwave and nighttime temperatures are key -Tends to affect the elderly, ill, poor, or socially isolated -Other effects include increased likelihood of drought, fire, and problems for infrastructure and agriculture Examples: Europe 2003, Chicago 1995, Russia 2010, Australia 2019 & 2020
Over warm water in the tropics (where hot air rises) is the ____ (and center of the Hadley Circulation)
ITCZ
What does an increase in greenhouse gases do?
Increase in greenhouse gases ---> less energy released to space --> more energy trapped near-surface and in atmosphere ---> Earth warms ---> A warmer Earth releases more longwave energy until energy balance is re-achieved (i.e. the radiation that comes in is balanced by radiation that is released to space).
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 & Bangladesh
Increasing greenhouse gas concentrations lead to warming temperatures in the Arctic. This, in turn, thaws permafrost in the region, releasing more methane and carbon, further increasing the greenhouse effect.
Positive Feedback
Due to failure in storage tanks, a huge amount of methane was released into Aliso Canyon, CA in 2015/2016, increasing atmospheric concentrations of the greenhouse gas.
Positive forcing
A positive radiative forcing warms the surface of the Earth. This leads to a warmer ocean. As the ocean warms, its ability to take up CO2 from the atmosphere is diminished. This means that more CO2 remains in the atmosphere, rather than being absorbed by the ocean. The increased greenhouse gas concentration warms the surface temperature further
Process describes a positive forcing
Hadley Cell Circulation
STUDY
ITCZ
STUDY
Many land areas, especially in the subtropics, will dry out (more evaporation into the warmer air, without much rainfall to replenish it) Where do we see this occurring?
SW US & Southern Europe
DOES NOT occur after CO2 is emitted to the atmosphere?
Some of the CO2 is converted to carbon monoxide
Within the Hadley cell, air masses converge (come together) at the surface close to which latitude(s)?
The equator (0 degrees)
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
Why isn't water vapor a forcing?
Water vapor itself cannot force changes in the climate, due to its short atmospheric lifetime, but atmospheric water vapor concentrations respond to and amplify temperature changes.
GHG must be polyatomic meaning
a molecule made up of more than one atom
Deserts occur where ___ is sinking (and away from storm tracks)
air
Globally, the rainy regions are where ___ is rising
air
Positive feedbacks lead to...
amplification of a forcing
A negative forcing results in...
cooling of the climate
Negative feedbacks lead to...
damping of a forcing
Between 1980 and the present, the European Union (EU28) has ________their carbon emissions, while the US has ________ their carbon emissions.
decreased; increased
Dry Heat
deserts heat up much faster during the day, but cooler at night
Feedbacks...
determine how much the temperature will change in response to a given forcing
So why does the US have higher per-capita emissions?
differences in total population
Feedbacks roughly ____ the amount of expected warming
double
Longwave Forcings
greenhouse gases are positive longwave forcings (all the ones mentioned above except water vapor) - Current CO2 radiative forcing: 2 W/m2 and rising - Total greenhouse gas radiative forcing: 3 W/m2 and rising
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
Warmer air has a _____ concentration of water vapor
higher
Developing countries are lower—why?
higher population
Global warming potential takes into account...
how much a gas warms the earth relative to CO2
The worst heat waves, in terms of human health impacts are often ______ , with particularly high mortality associated with high ________ temperatures.
humid; nighttime
Deforestation leads to an _______ in flooding
increase
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 __ evidence of human influence.
is
The Sun's rays strike the ground at a ____ direct angle at the polar latitudes (compared to the tropics). This is why the polar latitudes are cooler than the tropics.
less
With relatively few sunspots, the year 2005 was a time when the sun was emitting ____ radiation
less
Consider a scenario where the Earth is initially in energy balance and has a steady average global temperature. If the Sun suddenly dimmed, and put out less solar radiation, the Earth would no longer be in energy balance: the Energy In would be ____ than the Energy Out of the Earth system. In response the Earth would ____ until energy balance was restored.
less; cool
Sweating is ____ effective in a humid environment because ______________ cannot happen as easily.
less; evaporation
Scientists estimate that it is likely that the global average temperature will increase by 3 oC if CO2 concentrations double (compared to pre-industrial temperatures and concentrations). There is uncertainty within this estimate though. It is ______ that the temperature could warm by 4 oC in response to a doubling of CO2 It is _______ __________ that the temperature will warm by only 1.5 oC in response to a doubling of CO2
likely; virtually impossible
Mid-latitude rainy storm events are associated with regions of ___ pressure.
low
Midlatitude storm tracks determine where the other main rainy areas are. Series of high and low pressure systems generally move from West to East rainy areas are associated with _____ pressure
low
The aerosol indirect effect leads to a negative shortwave radiative forcing--more incoming sunlight is reflected away. This is because the presence of these tiny aerosols gives rise to clouds that are composed of ....
many small droplets
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
To get rain you need ____ __ & _____ ____
moist air & rising motion
This reduction in aerosols has also allowed ____ incoming solar shortwave radiation to reach the Earth's surface.
more
If Earth's planetary albedo increased, then ____ incoming solar radiation would be reflected away from Earth's surface/atmosphere. The Earth would no longer be in energy balance and so Earth's temperature would ____ until energy balance was maintained again.
more; cool
In the future, we expect that the tropics will experience ____ total rainfall, and that the subtropics will experience ____ total rainfall.
more; less
The sum of the "long-lived greenhouse gases" is higher than the "net total due to human activities." This is because _______ __________ forcings offset the greenhouse gas forcings.
negative anthropogenic
A particularly hot or cold year in a given location is ___ ________ indicative of climate change
not necessarily
Greenhouse gases are...
polyatomic (contains more than one ion)
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
Forcings are measured by
radiative forcing (W/m2) relative to preindustrial levels
Rainy places will get ______.
rainer -Also downpours will get stronger (rain intensity)
In regions of convergence (where two air masses meet) and uplift we expect it to be ...
rainy
Earth is heated by _____ radiation from the sun (high energy)
shortwave -342 W/m2 is the average incoming solar radiation (visible, near infrared and a small amount of UV)
US is rather high on this list, also oil-producing countries -why?
smaller population
The _________ part of the US is expected to experience the most months of the year that are similar to the worst days in the present. This is due to the projected regional increase in both temperature and ______ .
southeast; humidity
During heat waves, the air often becomes stagnant, trapping pollution. What does NOT accurately describe why pollution worsens heat effects on human health?
sulfate aerosol concentrations increase, absorbing more incoming shortwave radiation
Tropical monsoon migrates with ITCZ what season is the rainy season?
summer
anomaly
temperature anomaly means a departure from a reference value or long-term average. A positive anomaly indicates that the observed temperature was warmer than the reference value, while a negative anomaly indicates that the observed temperature was cooler than the reference value.
Earth would experience no distinct seasons if...
there was no tilt to Earth's rotational axis (the axis was vertical)
Scientists who are studying this stretch of warm days designated it a heat wave because...
these temperatures are among the hottest recorded for this area, which could cause stress for organisms that have adapted to live there.
Sunspots appear dark because
they are cooler regions & have a lower temperature
Shifts in rising motion can affect precipitation significantly this can lead to much
uncertainty in projections
During the monsoon's rainy season, land surfaces are relatively ____ compared to the ocean, and surface winds blow the air from __ _____ __ ___ ____.
warm; the ocean to the land.
Why will some places experience floods while other places will experience a drought?
warmer temp -> increased evaporation from the oceans --> a world with more water vapor -more energetic molecules that evaporate more readily more water vapor ---> increased rainfall -intensity increases water temperatures ---> increased evaporation from land surface -increased intensity of droughts warmer temperatures ---> shifts in oceanic patterns -pole-ward shift of arid subtropical zones (widening of Hadley cell) -Changes to el nino event (will discuss in ocean week) warmer temperatures ---> increased rainfall v. snowfall -water supply being out of phase with water demands
Carbon leakage:
when production of goods moves to a location with less strict regulation of emissions
When an air mass that contains water vapor meets a mountain it is forced to rise. The water vapor condenses, leading to more rain on the _________ side of a mountain. As the air descends on the other side of the mountain, it is dry. This describes ___________ ____
windward; orographic lift
the equation for climate sensitivity
ΔT =λ ΔF
