GEOG 303 - Midterm 1

How did Mark Twain describe the difference between weather and climate?

How did Mark Twain describe the difference between weather and climate?

“Climate is what you expect. Weather is what you get.”

Climate

The long-term average weather at a specific location or region

• includes mean values and ranges of what is ‘normal’

Weather

The specific state of the atmosphere at any point in space and time

• precipitation

• temperature

• snow

• winds

How many years do we use to calculate the climate ‘normal’

~30 years → more or less a generation

Variability

the interannual + decadal fluctuations around climate normals (mean state or averages)

How are adjustments made to the ‘normal’?

Repeated anomalies (slow adjustments)

What is more important than absolute temperature

anomalies

In terms of climate change studies what is an anomaly?

difference from an average or baseline temperature (set from an average of 30 years)

Positive anomaly

temperature is warmer than the baseline

Negative anomaly

temperature is cooler than the baseline

UNEP

United Nations Environment Program

Formed in Stockholm 1972

IPCC

Intergovernmental Panel on Climate Change

Formed by the UNEP and World Meteorological Organization (WMO) in 1988

UNFCCC

Unite Nations Framework Convention on Climate Change

Formed in Rio 1992 to cut down on greenhouse gasses

COP

Conference of the Parties (those in the UNFCCC)

1997 Kyoto COP3

Kyoto protocol is the first GHG emission reduction agreement

2010 Cancun COP16

Green climate fund is established to help reduce emission in developing countries

2015 Paris COP21

Agreement to limit the global average temperature increase (<1.5 C)

What happened in 2020 in regards to the Paris agreement?

The US pulls out (Trump)

In 2021 they return (Biden)

2023 UAE COP28

Discussion to move away from fossil fuels

Solar irradiance

the energy received on Earth from the Sun

Does solar irradiance have an effect on current rising temperatures?

It’s unlikely, but it did play a role in historical climate change

Key GHG (5)

• carbon dioxide - natural and anthropogenic sources

• methane - natural and anthropogenic sources (cow toots, organic matter decomposition)

• nitrous oxide - mostly from fertilizers

• chlorofluorocarbons (CFCs) - refrigerants, solvents and spray propellants

• water vapour

Atmosphere

mixture of gases that surrounds the Earth

what role does the atmosphere play? (4)

• shields us from the UV rays of the Sun

• traps in heat to warm the planet

• allows us to breath

• prevents extreme temp. differences btwn. day and night

what are the layers of the atmosphere? (5)

• exosphere - satellites

• thermosphere - aurora

• mesosphere - meteors

• stratosphere - planes

• troposphere - clouds

where do we find the most ozone?

stratosphere

______ is what absorbs UV to warm the planet

ozone

what are the two main gases in the atmosphere?

78% Nitrogen

21% Oxygen

Why is water not considered a greenhouse gas?

The residence time → it doesn’t stay long in the atmosphere

If the atmosphere was a bed what would the clouds be?

a blanket to keep the planet warm

what happens to atmospheric pressure as height increases?

it decreases

How can volcanoes have a massive cooling effect?

sulphur dioxide and ash release

Aerosols

particles in suspension in the atmosphere → can either aid in retaining heat or in reflecting heat

what happens when SO2 reacts with water?

forms sulphuric acid and sulphate aerosols that stay for up to 3 years

how does atmospheric movement occur?

driven by air pressure → warm air rises (low pressure), cold air falls (high pressure)

Pressure Gradient Force

  F_PG = ∆P/∆x

change in pressure over the change in distance

Coriolis effect

the force caused by the Earth’s rotation that deflects free moving objects from a straight line path

*important for atmospheric circulation

what are the global atmospheric circulation patterns?

upward motion at the equator from the most direct, highest and consistent incoming solar radiation levels

what does global atmospheric circulation patterns do to pressure?

creates low pressure at the surface and high pressure above

pressure gradient force (PGF) drives distribution of air towards the ______

poles

does the PGF ever reach the poles?

no, as it cools it begins to sink around 30˚N and 30˚S

what does cold polar air do in terms of atmospheric circulation patterns?

creates high surface pressure and causes mass air movement away from the poles, it is forced upward due to warming when it hits larger land masses (~60˚)

what is created when cold polar air hits large land masses?

a major jet stream

Why do we see trade winds and westerlies?

Coriolis effect

what are the important atmospheric forces? (3)

• gravity

• pressure gradient force

• Coriolis effect

*these are the primary drivers but they change t/o the year (driven by solar insolation)

Jet streams

faster upper-air westerlies associated w/ strong pressure gradients where the polar, Farrel and Hadley cells meet

what happens to jet streams when they meet with large patches of water?

They rise?wha

what happens to jet streams when they meet with large patches of land?

they dip

why is it faster to fly to Europe then to return?

You’ve been loaded up with bread.

JK, jet streams!

From a climate change perspective why do we care about jet streams?

They used to be more stable, but now especially in the winter they have started to fluctuate a lot

Drives the large weather systems (ex. -40 for two weeks, likely due to a jet stream)

How much of the Earth is covered by ocean?

~71%

How deep is the ocean?

Highly variably → average is 3800m, but the deepest point (Mariana’s Trench) is 11022m

what is the ocean’s composition?

96.5% H2O

3.5% dissolved salts, gasses, organics and other stuff

Why is the ocean salty?

run off from the rocks on land and openings on sea floor (lithosphere)

also plastic ☹ 🐢

salinity

refers to alll the dissolved ions in the water (ppt)

For a kg of sea water how much is salinity?

34.4g → 35 ppt

what are two factors that vary within oceans?

density and temperature

what drives the current in oceans?

Variety of density and temperature

why is density important?

in nature things want to reach equilibrium

How much denser is seawater compared to freshwater?

~3% → 1026 1026 kg/m³

with a salinity of 35 ppt, what does the freezing point become?

-1.8˚C

how do we gain a knowledge about the ocean?

Sampling!

monitoring buoys and remote sensing to collect data

Are the controls of salinity constant?

No, its a cycle of increasing and decreasing

Why might the controls of salinity increase? (2)

Evaporation of seawater

Freezing of seawater

Why might the controls of salinity decrease? (4)

Precipitation of rain and snow

Melting of ice

River runoff

Groundwater flow to ocean

*all of these dilute the ocean

What kind of forces cause the movement of oceans?

• friction from the winds and tides

• Internal friction btwn the layers of water

• friction against the ocean floor

• PGF and gravity also

what are Gyres?

large rotating ocean currents

oceans have a ______ thermal heat capacity

high

what is a high thermal heat capacity good for?

moving heat around the globe

What are slow deep ocean currents?

Cold + saltier (denser) water that sinks to the bottom, warm water then flows to fill the surface area

are currents 2 dimensional?

No! they’re 3 dimensional

Thermohaline Circulation

warmer water rising + colder water sinking

Why are ocean currents important?

• movements of nutrients and phytoplankton

• control of weather conditions

• Oxygen → circulates it around the Earth

Where is ice stored?

• Greenland and Antartic ice sheets

• Mountain glaciers, icefields, and ice caps

• seasonal snow

• sea ice

• ground ice/permafrost

what are the components of the Cryosphere?

• seasonal snow

  • most important part for global weather and community

  • important for water resource availability

• Sea ice

  • large influence on Arctic climate; changing sea ice also affects weather patterns

Sea ice formation:

• temperature must drop below 1.8˚C

• cover begins as “plates” or “pancake ice”

• pancake ice fuses to give continuous ice cover

what are breaks in sea ice called?

leads (linear) or polynya (large 2D openings)

how thick is sea ice

it depends how old it is but ~2-5 m thick

what is depth of sea ice controlled by?

• overlying snow (insulation)

• air temperatures

• ocean heat flux (melting from the bottom)

• ice ridging (smashing together)

How does sea ice move?

moves with the currents

what is the land distribution of Greenland?

• 84% ice

• 15% barren

• 1% cultivated pasteur (where people live)

what is the highest point of greenland?

Gunnbjorn → 3700m

what is the world’s largest desert?

Antarctica

what is the land distribution of Antarctica?

98% ice

2% bare rock

what is the highest point of Antarctica?

5140m

approximately how much ice per year has Antarctica lost btwn 2002 and 2023

150 gigatons

with ice melting in Antarctica how much does the seal level rise every year?

0.4 mm

approximately how much ice per year has Greenland lost btwn 2002 and 2023?

270 gigatons

with ice melting in Greenland how much does the seal level rise every year?

0.8 mm

which part of Antarctica melting the fastest and how much?

west

losing volumes that equal the weight of Everest every 2 years

Permafrost

Ground that stays below 0˚C for two years or more

continuous permafrost

90-100% of landscape

Discontinuous permafrost

50-90% of landscape

Sporadic permafrost

0-50% of landscape

in the northern hemisphere how much of land area is covered by permafrost?

25%

how much could an increase of 3˚C thaw the top layers of permafrost?

30-85%

what impacts does permafrost thawing have?

• slumping

• damage to infrastructure

• CH4 (methane) release allows microbes to consume organic material

• flooding hazard

Contents of Land Surface that influence Climate

• surface albedo (reflectivity) → increase in albedo decreases temp.

• evapotranspiration from vegetation and evaporation from bodies of water

• geochemical and hydrologic cycles - including the carbon cycle

• surface roughness and impacts on winds

• surface heat capacity

how do we identify anthropogenic CO2?

• isotopes → Carbon 13 (naturally occuring), 14 (radioactive doesn’t last long) - 12 (fossil combustion) is found in plant material and is increasingly replacing 13+14

• atmospheric O2 levels (ratio of O2:N2) is decreasing

what does the carbon cycle consist of?

Sources and Sinks (stocks and flows)