GEO011H Midterm 1 Study Guide

How is the climate different than weather?

How is the climate different than weather?

climate varies more slowly than the weather and is highly predictable, as climate encompasses the typical patterns of temperature and precipitation caused by droughts, floods, hurricanes, tornadoes, blizzards, and heatwaves.

Define "climate".

average of many years' worth of weather while the weather is the actual state of the atmosphere at a particular time.

Why is climate predictable?

this predictability stems from the relatively fixed features of the Earth including Earth's spherical shape, the shape of its' orbit around the sun, a tilted axis of rotation, as well as the natural factors of oceans, continents, and a multilayered atmosphere composed of greenhouse gases GHGs.

What is meant by climate change?

The process of climate change refers to a change in global or regional climate patterns, in particular, a change apparent from the mid to late 20th century onwards and attributed largely to the increased levels of atmospheric carbon dioxide produced by the use of fossil fuel, ex: sea-level rise, temp increase, shift from one state to another state.

How is sunlight related to latitude?

The amount of sunlight depends on latitude, so the poles are cold as the solar radiation is dispersed and the tropics are hot as solar energy is concentrated.

What is the feature of seasonal contrast with latitude?What is the cause of the seasons?

Tropics have a low seasonality while mid to high latitudes have high seasonality, as seasons are caused by the tilt of Earth's spin axis. Seasonality determines how hot the summers are and how cold the winters are.

How and why do oceans influence seasonal contrast? How do oceans influence climate?

Water has a high capacity for storing heat, so coastal regions benefit from the ocean's moderating influence (oceans warm slowly in summer, cool slowly in winter).

Be familiar with several important warm currents and cold currents, such as the Gulf Stream, Kuroshio and California Current.

Gulf stream and Kuroshio warm currents low to high latitudes, CA current cold current high to low latitude

What kind of climate is in Southern California?

CA Mediterranean climate hot dry summers mild relatively wet winters (latitude about 32 degrees N and cold CA current) wet winters like climate around Med seas

Be familiar with atmosphere layers and vertical temperature distribution in each layer

Troposphere, stratosphere, mesosphere, thermosphere, exosphere; troposphere as height increases temperature decrease, stratosphere as height increases temp increases, zigzag pattern up

Where does weather occur?

Troposphere

Where is the ozone layer?

Stratosphere

Where is the ozone hole?

Antarctica

How are CFCs related to the ozone hole?

Chlorofluorocarbons (CFCs) accelerate destruction of ozone, reducing it's abundance and ability to protect the planet from UV radiation.

Be familiar with the general circulation of the atmosphere

3 cells, Hadley, ferrel and polar;

What is a Hadley cell?

a large-scale atmospheric convection cell in which air rises at the equator and sinks at medium latitudes, typically about 30° north or south; dry air towards the equator and tropical air away from the equator

What is the ITCZ (Intertropical Convergence Zone)?

An area of low pressure where air converges warm moist air rises as rising air in the tropics draws surface air in from the trade winds (higher latitude).

Why are the tropics rainy?

Water evaporates & becomes water vapor -a gas that composes the lower atmosphere.
Like a huge hot-air balloon, air near the ground in the tropics warms as a result of solar radiation, becomes buoyant, and rises.
As the warm tropical air rises, it expands and cools.
Cold air can hold less water vapor, so as rising tropical air cools, water condenses out as rain droplets, forming towering cumulus clouds and thunderstorms.

Where do most of the world's deserts exist

subtropical latitudes; Air rising in the tropics moves poleward once it reaches altitude. This poleward flow gets deflected and air sinks in the subtropics.
This air is dry because most of the water vapor was precipitated out of it when it previously rose. Also, as air descends, it gets compressed and warms.

Where are jet streams located?

The subtropical jet is located above near the convergence of the Hadley and Ferrel cells, and the polar jet is located above the Polar Front (convergence of Ferrel and Polar cells)

How will climate change affect the location of the polar jet stream and the subtropical dry zones?

shift poleward

What is the implication of this migration?

penetration of dry air in higher latitudes

What are greenhouse gases (GHGs)?

methane (NH4), water vapor, Nitrous oxide (N2O), carbon dioxide, CFCs (only non-natural)

Are they abundant gases in our atmosphere?

no, trace gases measured in ppm and ppb but large effect

What are the lifetime periods of GHGs (CO2, CH4 and N2O)?

CO2 very long, CH4 decade, N20 100 years

What are the primary sources of anthropogenic GHGs?

fossil fuel burning, deforestation, agricultural practices

What is meant by "global warming potential"?

Defined as the increase in greenhouse effect caused by the release of a kilogram of that gas, relative to that produced by an equivalent amount of CO2.

What evidence do we have that the world is warming?

Independent temperature data from the atmosphere, the ground, and the ocean sub-surface, combined with evidence such as melting snow, ice and permafrost, rising sea levels, and observed changes in plant and animal behavior make it clear that Earth is warming noticeably.

How much has global average surface temperature increased over the ∼20th century?

Global temperature has increased by nearly 1.0°C (1.8°F) since 1880. This is ~25% of the estimated change in global temperature during the last Ice Age, when NYC was covered by an ice sheet 0.5 km thick.
Rate of warming accelerating: 0.10°C/decade over the 20th century; 0.15°C/decade in past few decades

What is the preindustrial atmospheric CO2 level and how much has atmospheric CO2 increased since preindustrial times?

Has increased 1 degree celsius, preindustrial CO2 level was 280ppm (now 400 ppm) 40% increase

Are these changes of CO2 and temperature large relative to past CO2 and temperature variations over the geologic record?

Global CO2 records have been higher, but the rapidity of CO2 increase from anthropogenic factors makes Anthropocene dangerous

What is the IPCC?

Intergovernmental Panel on Climate Change (IPCC) was established in 1988 to evaluate the risk of human-induced climate change, and its periodic assessment reports are the authoritative source for accurate information.

What are some of their climate projections for the late 21st century?

Virtually certain: cold days and nights will be warmer and less frequent over most land areas; the extent of permafrost will decrease; oceans acidification will increase as the atmosphere accumulates CO2, northern hemisphere glaciation will not initiate before 3000; global mean sea level will rise and continue to do so

How does the IPCC account for uncertainty?

AR5 presents conclusions in terms of the likelihood of particular outcomes, expressed as a probability based on the quality, volume and consistency of the evidence of extent of expert agreement.

What is water vapor feedback?

Adding CO2 to the atmosphere warms the planet. This causes more surface water to evaporate, increasing atmospheric water vapor. Since water vapor is also a greenhouse gas, the planet will then warm even more "water feedback loop" positive feedback because it amplifies initial change.

ice-albedo feedback

a positive feedback climate process where melting of snow-covered land, ice caps, glaciers or sea ice decreases the albedo.

low cloud feedback

low clouds reflect solar energy to space- negative feedback

How are positive feedbacks different from negative feedbacks?

positive amplifies initial change while negative decreases initial change

What is the net impact of feedbacks on Earth?

Increase expected warming/cooling due to imposed change; positive feedbacks outweigh negative

What is albedo?

reflectivity of solar radiation back to space; the planetary albedo is about 1/3.

What are the natural factors that influence climate?

Solar radiation, Earth's orbit (milankovitch cycles) volcanic eruptions

What are the anthropogenic factors that influence climate?

fossil fuel burning, deforestation, agricultural practices

How do industrial aerosols affect climate?

some aerosols (carbonaceous black carbon) can, like GHGs, have a surface warming effect.

Volcanoes (on short time scales)?

cooling as aerosols reflect/absorb incoming sunlight that would otherwise warm Earth's surface.

What is the difference in climate impacts between aerosols and GHGs?

GHGs more global compared to regional influence

How do we know the increase in CO2 since preindustrial times is caused by human activity?

Fossil fuel burning more than accounts for the recent rise in atmospheric CO2.
In fact, the recent rise equates to only half of what we have released into the atmosphere-the other 50% has dissolved into the ocean or been taken up by forest growth.

How are carbon isotopes involved? What are the isotopes of carbon?

C-14: radioactive, seen in tree rings, decreasing
Increase in radiocarbon dead C-12 from fossil fuel burning
Decrease in ratio b/w C-13 and C-12
bad carbon heats troposphere, decreases atmospheric radioactivity, no natural sources

What is the carbon cycle? Why is it important? What are the reservoirs of carbon in a carbon cycle?

Carbon is cycled through various reservoirs (air, plants, soil, decomposers)this cycle of uptake and release are balanced.

How have humans perturbed the carbon cycle?

added burning coal to carbon cycle increasing atmospheric carbon dioxide so more carbon dioxide produced than natural ratios

Do all of our CO2 emissions stay in the atmosphere? If not, where do they go? What does this imply in terms of the magnitude of global warming/climate change?

No, 50% into oceans and forests, double the Co2 emitted

What is the greenhouse effect and how does it work?

On Earth, the greenhouse effect occurs because we have greenhouse gases, which absorb heat, which then warms the atmosphere.

How will it affect atmospheric temperature (troposphere vs stratosphere)?

Warms troposphere and cools stratosphere

Does it occur naturally? How have humans perturbed it?

yes, but humans driven up atmospheric CO2 concentration with fossil fuel burning, deforestation, agricultural practices

Where is most of the GHG-induced heat going?

ocean

How does this affect sea level?

rise

What is ocean acidification?

refers to a reduction in the pH of the ocean over an extended period of time, caused primarily by uptake of carbon dioxide (CO2) from the atmosphere.

How does climate change affect O2 levels in the ocean? Why?

Less O2 dissolves into oceans, including the cold, dense polar oceans that sink to the deep sea and provide essential oxygen to organisms living at depth.
Warming also reduces the tendency for this water to sink by making it less dense, further isolating the oxygen-depleted deep waters from oxygen-rich surface waters.

List several climate "proxies". Why are they useful? What do they tell us?

tree rings, corals, ice cores, lake sediments, documentary evidence
Since there are no thermometer records or samples of ancient air from the geologic past geologic "proxies" are characteristics of sedimentary rocks that we can use to infer ancient environmental conditions.
Proxies may even include the pores (stomata) on fossils of leaves: when atmospheric CO2 levels are low, plants need more pores to bring in more CO2.
Comparing the pore density to a living plant allows an estimation of past CO2 levels.

Has Earth's climate been very stable over geologic time intervals?

no, glacial-interglacial cycle
EX: 20,000 years ago glacial climate with ice sheets covering much of North America and Scandinavia.
Prior to 2 million years ago no large ice sheets in the Northern Hemisphere.
Prior to 34 million years ago no large ice sheets anywhere.

How are ice cores used to infer past climates? What do paleoclimate data indicate about long-term temperature and CO2 variations?

Scientists extract the gas from tiny bubbles in the ice core to measure the concentration of ancient air; Three GHGs have been rising at dramatic rates for the last two centuries. CO2 increased by 40%;
CH4 by 150%; N2O by 20%
Driven by fossil-fuel burning, deforestation and agriculture, the recent skyrocketing trends greatly exceed the natural fluctuations of the preceding hundreds of thousands of years
From ice cores, the last interglacial had atmospheric CO2, CH4 and N2O levels close to pre-industrial.

Pleistocene, Last Glacial Maximum, Holocene, Eocene Optimum, Pliocene, Anthropocene, Little Ice Age, Medieval Warm Period, Last interglacial

Eocene optimum: 56-49mya alligators and sequoia forests were thriving above the Arctic circle.
Pleistocene Epoch: glacial 2 million years ago until 10,000 years ago; fluctuations in sea level are the result of 40,000 and 100,000-year "glacial-interglacial" cycles of the last 2 million years
Pliocene: 5.3 to 2.6 million years ago, was a time of global cooling
Last Interglacial: 125,000 years ago
LGM: 22,000 years ago,
Holocene: last 10,000 years-most recent interglacial period.
Medieval Warm Period: 10th-13th centuries
Little Ice Age: 15th-19th centuries
Anthropocene: Industrial Revolution to Present, unprecedented GHGs, human alteration of the atmosphere

Milankovitch cycles

Changes in the shape earth's orbit and tilt that cause glacial periods and interglacial periods (eccentricity, tilt of Earth's spin axis, precession-wobble)

What orbital cycles are important for climate? What are their periods, respectively?

Orbital ellipticity (100,000 year cycle)
Precession: wobble (19,000 and 23,000 year cycles)
Tilt (41,000 year cycle)

Are these fast or slow processes (on human timescales)?

slow

Why is the last interglacial warm enough to melt the Greenland icesheet?

Northern Hemisphere received 10% more solar radiation than it does today (not because the sun is brighter, but because Earth's orbit around the Sun was different than it is today).
Due to slow changes in Earth's orbit around the sun, caused by gravitational tug of the Sun, moon, & the large planets ("Milankovitch Cycles").

How will climate change affect drought?

intensifies drought especially in western US; Drought pattern has afflicted much of western North America, American tropics, Africa, Asia, Indonesia, & Australia.

For the western U.S., how is drought related to tropical Pacific sea surface temperatures (SSTs)?

La Nina like conditions; Anomalous cold eastern tropical Pacific SSTs with hot western tropical pacific SSTs

What is El Nino?

warming in E pacific; an irregularly occurring and complex series of climatic changes affecting the equatorial Pacific region and beyond every few years, characterized by the appearance of unusually warm, nutrient-poor water off northern Peru and Ecuador, typically in late December.

La Nina

cooling in equatorial E. pacific; A cooling of the ocean surface off the western coast of South America, occurring periodically every 4 to 12 years and affecting Pacific and other weather patterns.

How will climate change affect record high temperatures/heat waves?

more record highs and heat waves

Record low temperatures/cold snaps? How will extreme warm/cold events change with global warming?

does not affect overall climate change; more record highs less record lows

How will climate change likely affect hurricanes?

stronger hurricanes, more stronger hurricanes, less hurricanes in general

Why is Hurricane Sandy so powerful?

It merged with an extra-tropical, wintertime cyclone.
Climate change raised sea surface temperatures (SSTs) along the eastern coast of the U.S.

How has climate change affected the cryosphere (Arctic sea ice, mountain glaciers, ice sheets, etc.)?

melting

How does this (land-based ice), in turn, generally affect sea level?

causes it to rise

What is a "simple" climate model based on

focus on the balance of incoming solar energy and outgoing terrestrial (heat) energy.
This balance determines a planet's surface temperature
accounts for the greenhouse effect, feedback loops

What are General Circulation Models (GCMs)? Should they be trusted? Why or why not?

take into account the 3D structure of atmosphere and ocean, arrangement of continents, surface topography, ocean basins, coastlines, etc.; trustworthy as grid boxes obey laws of physics

What do climate models tell us about natural variations and the warming since the 1970s?

Indicate natural variations do not explain the warming since 1970s
Indicate GHGs have driven the bulk of the warming since 1970s
Reproduce observed T trends when both natural and human factors are included.

What is the climate zone of Southern California?

Mediterranean

What are the impacts of climate change on climate zones and biological diversity?

Loss of Arctic sea ice polar bears
Disappearance of Alpine tundra in North America American pika
Amazon Basin forest loss due to aridification; wildfires
Tropical species may be especially threatened, as tropical temperatures vary over a smaller range and the natural range of animal species are inherently smaller. Small shifts in Temperature greater adaptive challenge.
Many areas where existing climates may disappear (Andes, Mesoamerica, southern and eastern Africa, Himalayas, Philippines) are regions of currently large biological diversity potential for species loss is particularly high.

In the context of climate change, what is meant by a "fingerprint"? Why are finger- prints useful? What do they tell us?

One way to distinguish between natural and human causes is to look for "fingerprints" specific patterns of change that help to identify the likely underlying factor associated with that change.
Natural factors include changes in solar output and volcanic eruptions.
Human factors include greenhouse gases and industrial aerosols.