Global climate change | spring term 2025

First in person quiz

Week one lecture

The climate system

• atmosphere

• geosphere

• hydrosphere

• biosphere

Weather vs. Climate

Weather describes atmospheric conditions at a specific place at a specific point in time

Time frame is short:

• minutes, hours, days, weeks

figured out by real time measurements of the atmosphere’s pressure, temperature, wind speeds and directions. As well as humidity precipitation, cloud cover, etc.

Climates refers to the average pattern of weather over a longer time period

Time frame is longer:

• months, years, decades (the usual climate known/seen)

What determines the climate for a particular location?

• sunshine

• trees/vegetation

• wind, precipitation patterns

• topography, mountains

• greenhouse gases

What is climate change?

Climate change refers to significant alterations in temperature, precipitation, and other atmospheric conditions over extended periods, primarily driven by human activities such as the emission of greenhouse gases.

Week two lecture

Earth - The Geosphere

Earth is a complex system composed of four main components or spheres.

• geosphere - solid earth

all of the earths matter. earths surface down to core. rocks, and mountains.

layers like crust upper mantle, lower mantle, outer core, and inner core

• hydrosphere - water

• atmosphere - air

• biosphere - life

they all interact with each other

change in one sphere can lead to changes in the others

Volcanic Eruptions

Gases that come from eruptions

• CO2

• H2O

• SO2

Atmospheric Composition

our atmosphere is mostly

• Nitrogen (N2, 78%)

• Oxygen (O2, 21%)

• Argon (Ar, 0.9%)

Atmospheric Trace Gases

• CO2 - carbon dioxide

• CH4 - methane

• O3- ozone

• N2O - nitrous oxide

• CO - carbon monoxide

• NOx - nitrogen oxides

• SO2 - sulfur dioxide

• plus hundreds others

Called traces gases because they leave traces in the air while other gases don’t, they exist in low concentration, important for the atmosphere.

Water Vapor

• gaseous formed of water - H2O

• known as humidity

Water Vapor in the atmosphere

1. highly variable

2. strongly controlled by temperature

The saturation point

• The maximum (most) amount of water vapor that can exist in air

• The saturation point goes up exponentially with temperature - leads to atmospheric humidity goes up

Warmer places have higher saturation points for water vapor

• air has more water vapor = high humidity

How do we find out if the air is close to saturation point?

we use RH!!! (relative humidity)

RH = Actual humidity over Saturation humidity at the air’s temperature

Over 70% of the earth’s surface is water!

Because there is so much water it takes a lot of energy to change water’s temperature

• known as heat capacity

The big two

Temperature - in climate science we often look at sea surface temperatures, abbreviated SST

Salinity - how much salt is dissolved in the water (saltiness)

Differences in density of water help with?

global ocean circulation, helps distribute heat and gases like CO2 and O2

Cryosphere - Earths frozen water

can be:

• sea ice

• ice sheets

• permafrost

• glaciers

• snow cover

Biosphere

plants absorb CO2 from earth’s atmosphere for photosynthesis

Week three lecture

Energy cannot be created or destroyed, only transferred or transformed

• Energy = Conserved

Radiation means electromagnetic waves

Wavelength

• wavelength is the distance between two crests of the wave (units of length)

there are short wavelengths (more waves short distance) and long wavelengths (less waves more distance)

• high frequency = less distance between wave

• low frequency = more distance between wave

Radiation and Matter

All matter emits radiation - emission is controlled by the matter’s temperature

• higher temperature = more radiation emitted

• higher temperature = more energetic radiation emitted

Albedo

Albedo = A = Energy reflected over Energy in

Earth’s Albedo is about 0.3 mean of albedo measures indicates that approximately 30% of incoming solar radiation is reflected back into space, which plays a significant role in regulating Earth’s temperatures.

How do i know if it’s a Greenhouse gas?

• they rotate, vibrate. meaning they absorb long wave radiation

• molecule must have some level of polarity

Positive forcing: energy in causes climate to warm

Negative forcing: energy out causes climate to cool

Amplifying feedbacks: positive feedbacks

Damping feedbacks: negative feedbacks