Winguth Global Warming Final Review

Definitions of weather and climate and differences between the two

Weather is the instantaneous state of the atmosphere around us, consisting of short-term variations such as temperature, precipitation, humidity, air pressure, cloudiness, radiation, wind, and visibility. Weather is a daily effect. Climate is the statistics of weather over a longer period.It is the average weather that varies slowly over periods of months, or longer. Climate is potentially predictable if the forcing is known because Earth's average temperature is controlled by energy conservation. Climate varies from weather in that climate is the long-term, stable, and expected values of temperature and weather is the volatile and minimally predictable changes.

Predictability of weather vs. climate?

Climate is much more predictable than weather because climate is the consistent average of a given area. Weather is less predictable because it is observed on a much smaller scale and it is much more volatile due to a variety of factors.

What are the main components of the climate system?

Cryosphere, biosphere, ocean, carbon cycle, lithosphere

What is being exchanged between the different parts of the climate

system?

Energy, water, momentum, and carbon are being exchanged in the climate system.

Examples for these processes/exchanges?

Imagine water evaporating from the tropical ocean heated by the sun (Fig. 1). The air containing that water rises and cools. The water condenses into a cloud. The cloud is carried by winds over land where it rains. The rain sustains a forest. Trees are dark, having a low albedo. This influences the amount of sunlight absorbed by the Earth

What is radiative forcing? What causes it?

Rative forcing is the change in the radiative balance (The amount of energy reaching an object and the amount leaving it) at the top-of-the-atmosphere (the tropopause) for a given change in one specific process that affects those fluxes with everything else held constant. Examples for such a process are changes in greenhouse gas concentrations, aerosols, or solar irradiance.

What are positive and negative feedbacks? Examples from the climate system

Positive feedbacks are feedback loops wherein an initial force causes a response that becomes amplified. Negative feedback loops are loops wherein the initial response is reduced within the loop.

How have the numbers of "billion -dollar disaster events" and the costs in the US

changed over the past decades?

While the number of events has remained relatively the same, the intensity and cost of these events has increased significantly.

What is the relationship between extreme weather events and climate change?

Climate change is the steady increase in global temperatures whereas extreme weather events are a result of climate change.

Anthropogenic climate change = human-caused climate change

Anthropogenic climate change releases aerosols from the burning of tropical forests and fossil fuels and is a contributor to human-caused climate change.

Global temperature measurements: since when do they exist, how are they averaged globally? Why are temperature anomaly records used, rather Than absolute temperature values? What should be the minimum number of years used

as a base period?

The earliest global temperatures have been cataloged since the 1850s.

If only the absolute temperatures were recorded the change in temperature wouldn't be as easy to detect.

30 years

By how much has global temperature increased over the last century?

About 1 degree C

Which areas have heated up the most (and why)?

The area that has heated up the most is the arctic region. It is happening because of the albedo effect, as the sea ice disappears more of the heat from the sun is being absorbed causing an increase in temperature in the region.

What is Earth's cryosphere?

Sea Ice (Artic, Greenland, and Antarctic), Ice Sheets, Glaciers, seasonal snow cover, permafrost

Recent trends in Arctic sea ice extent, thickness, volume

Since about 1970, sea ice has been noticeably shrinking in thickness and volume. Also, the age of the sea ice has been reduced due to increased melt during the warmer periods.

By how much would global sea level approximately change if the

Greenland Ice Sheet, the West Antarctic Ice Sheet, or all of the Antarctic ice

Melted?

If all of Greenland's ice melted, then the sea would rise around 7 meters,

West Antarctica: 6 meters

All of Antarctica: 60+ meters

Why might collapsing ice shelves accelerate ice sheet decline?

As the ice shelves collapse they reduce the support for the ice sheets and reduce the structural integrity of the ice sheets; they are thinner areas of ice, thus they will melt quicker reducing ice albedo effect

What is permafrost? How does its melting influence the climate system?

Frozen soil that has been frozen for at least 2 years and the important thing to remember is that there is a lot of bacteria trapped within the soil and it produces a lot of methane and other greenhouse gasses. As permafrost melts, lakes and pools form where flat land once stood.

By how much has global sea level risen over the last century?

0.2 meters

How is the global sea level being monitored?

Thermometers, Statelights

What has been the rate of sea level rise during the past 2-3 decades? What are the

major causes for this rise?

Thermal expansion, ice cap melting, glacier, ground water

3.4mm +/- 0.4mm every year (about a 90mm increase during this period)

Observed trends over the past decades in ocean heat content, heat waves,

precipitation extremes and distribution

Increasing in all categories

How has hurricane intensity changed in recent decades, and what is the likely

cause for this change?

Intensity of hurricanes increases because warm air can hold more water.

Characteristics of the Sun, the driver of Earth's climate (e.g. TSI, temperature in

Sun's core and at the surface)

Core temperature: ~15 million Kelvin

Surface temperature: ~6000 Kelvin

What are sunspots, how do they influence the TSI? Recent sunspot activity?

Cyclicity?

Sunspots are produced by the magnetic field and are cooler regions that make the TSI overall higher; 11-year cycle, 22-year cycle, 2,300-year cycle, 6000-year cycle

Very active until 1978; does not explain global warming

Characteristics of orbital cycles/orbital parameters, their effect on incoming

radiation and Earth's climate; Milankovitch Cycles

These influences can reduce or increase the radiation. The Milankovitch cycle relates to periods in earth's history that the planet is farther and closer to the sun.

Orbital Eccentricity: Circular/slightly elliptic, distance from sun varies, 100,000-400,000 year-cycles

Obliquity: Tilt of Earth's axis, 22.1 to 23.4 degrees, 41,000-year cycles

Precession: Axis rotates, direction of tilt towards sun varies

Greenhouse gasses and their sources

• Carbon dioxide-fossil fuel burning, deforestation

• Methane-sometimes natural, wetlands/termites, but also energy/ruminates/landfills/ rice agriculture

• Nitrous oxide- sometimes natural, bacterial/microbial activity, but also Agriculture, Engines, Medicine, Aerosol, Biomass burning

• Ozone-naturally occurring in the stratosphere, but produced into the troposphere with biomass burning and car exhaust.

• Halocarbons- chlorofluorocarbons, from air conditioning, refrigeration, insulations

Keeling curve (current approximate CO2 level?)

The keeling curve is a graph that shows the concentration of carbon dioxide in the atmosphere since 1958. It rises in an awfully consistent way.

Ozone in troposphere and stratosphere, impact on climate

Ozone in the troposphere is BAD, that's a greenhouse gas. Ozone in the stratosphere is a good thing, that's normal.

Electromagnetic radiation: ultraviolet, visible, infrared - how do they differ in

wavelength and energy transport

Ultraviolet radiation as the wavelength is the tightest between the 3 and transports the most energy between the 3, visible is the middlemost wavelength in size/transportation, infrared is the loosest and biggest and transports the least energy between the 3. (Ultraviolet like ultra-violent, like this radiation could hurt you and is fast, infrared like red, like a lazy red-eyed stoner, it's slower and lesser)

Incoming solar radiation at top of atmosphere vs. ground level; Distribution of

incoming energy at ground level?

1.8% irradiance at the top of the atmosphere

0.3% irradiance at sea level (ground-level)

Distribution is clear at the top of the atmosphere; at sea level there is more "mixing"

What is the average irradiance received at the top of Earth's atmosphere?

The average irradiance according the textbook graph is above 1.5 and below 2, around 1.75 (W/m(to the second power))

Incoming vs. outgoing radiation

Incoming radiation is S=342Wm(-2)

General idea about Earth's energy budget, e.g. How much of the incoming solar energy is absorbed at ground level?

Out of the incoming value 341, the absorbed value is 161.

What happens to the "rest" of incoming solar energy?

The "rest" of the solar energy is reflected, or about 30% of the energy that is non-absorbed

How much incoming energy is reflected vs. emitted as heat energy?

About 29% of all incoming energy is reflected, 50% is emitted off earth as heat energy

What is the "atmospheric window"?

The atmospheric window is a section of the electromagnetic spectrum that can be transmitted through the atmosphere in specific channels.

Greenhouse effect and enhanced greenhouse effect

what makes greenhouse gasses different from the main constituents of the atmosphere

Greenhouse gasses have structures that absorb heat, and keep heat, while the main constituents of the atmosphere allow heat to pass and reflect off the surface of the planet

What is radiative forcing? What can cause it? Approximate total anthropogenic Forcing?

Radiative forcing is the change in the balance between Earth's incoming and outgoing radiation. The changes can be caused by changes in greenhouse gas concentrations, solar irradiance, aerosols.

What is global dimming? Example: Mt. Pinatubo eruption in 1991

Reduced sunlight reaching the surface of the earth because of the increased pollution in the air. Global warming has increased global dimming.

What is the difference between climate sensitivity and radiative forcing?

Radiative forcing is the imbalance of incoming and outgoing energy resulting in climate change. Climate sensitivity is the degree of which the climate will be affected by the increase in carbon dioxide.

Carbon reservoirs in the Earth system, relative sizes

Atmospheric carbon reservoir - 750 GtC (gigatonnes)

Ocean - 40,000 GtC

Biosphere - 619 GtC

Examples - forest fires and fossil fuel combustion and outflows from plant growth and uptake by the oceans

Sources of anthropogenic carbon

Power generation, transportations, industrial sources, chemical production, petroleum production, and agricultural practices

What is the evidence for anthropogenic activities being the main sources for

atmospheric CO2 increase? What can be derived from atmospheric carbon

Isotope studies in this context?

The isotopic composition of atmospheric CO2 can be measured and shows that CO2 being added to the air now comes from combustion of fossil fuels. The increase also aligns with the industrial boom. This can help us understand the natural carbon cycle's response to human activities.

Why is the increase in atmospheric CO2 also causing ocean acidification?

Because of human-driven increased levels of carbon dioxide in the atmosphere, there is more CO2 dissolving into the ocean, this raises the oceans average pH and it becomes more acidic.

Unequal heating of the Earth's surface, resulting temperature gradient, energy

imbalance between low and high latitudes, meridional heat transport

Atmospheric circulation cells and surface winds, areas of high and low pressure

Clockwise patterns in the southern hemisphere cause high pressure and counterclockwise patterns in the northern hemisphere cause low pressure.

Coriolis effect, impact on flowing air and water

The Coriolis effect makes storms swirl clockwise in the Southern hemisphere and counterclockwise in the Northern Hemisphere, it is a force that explains the paths of objects on rotating bodies and is caused by the earth's rotation.

What are jet streams and ITCZ?

The Subtropical Jet Stream is a region of strong winds in the upper troposphere between 20°- 40° latitude. The Intertropical Convergence Zone (ITCZ) is a convective region of thunderstorms separating the northeast and southeast trade winds.

Latitudes with dry and wet conditions (location of deserts)

Many deserts are located around 30* while many wetlands are located around 60* both north and south as well as the equator.

How do phase transitions of water within the hydrological cycle contribute to energy transfer in the climate system?

The energy absorbed is latent heat and goes back to the environment when the phase changes reverse

What is latent heat?

Latent heat flux is the flux of energy from the Earth's surface to the atmosphere that is associated with evaporation or transpiration of water at the surface and subsequent condensation of water vapor in the troposphere

What is "special" about water's specific heat?

It takes a lot of energy to heat it, water has to absorb 4,184 Joules of heat for the temperature of one kilogram of water to increase 1°C

Resulting heat uptake of ocean vs. atmosphere?

Oceans have absorbed around 90% of excess energy (in the form of heat)

Ocean temperature distribution, because of circulation, is more of a gradient (gradual decrease of temperature towards the poles) In the atmosphere the temperature distribution is more direct (rapid changes in decreasing temperature towards the poles)

Surface ocean circulation:

gyres, warm vs. cold currents, tropical divergence

Warm water on the west side of the gyre and cold water on the east side.

Characteristics of the Gulf Stream and the Antarctic Circumpolar Current

brings very cold water up from the bottom.

The Gulf stream brings warm water to Europe and slows down with fresh water from melting ice. The circumpolar from the arctic brings very cold

Temperature and salinity distribution in surface ocean waters (general pattern)

Areas with higher evaporation tend to have more salinity, thus higher temperature and less precipitation directly causes an increase of salinity. Also areas with more ice also have higher salinity

Thermohaline circulation, its main driver, what are NADW and AABW?

The movement of water in the Earth's oceans

Colder and saltier water are more dense causing deepwater formations

NADW: North Atlantic Deep Water

AABW: Antarctic Bottom Water

Tropical cyclones:

formation over warm tropical ocean, important heat transfer mechanism