Weekly Lectures

Week One: How Long Have We Known?

  • Society has become more polarized with its opinion of climate change

  • Stockholm Cosmic Physics Society was established in 1893, members included: Arvind Hogbom, Nils Ekholm, Svante Arrhenius, and Vilhelm Bjerkne

  • Hogbom identified six sources of carbon dioxide in the atmosphere:

    1. Erupting volcanoes

    2. Meteorites

    3. Vegetation as it decomposes or burns (ex: burning of coal and oil)

    4. Release of carbon trapped in rocks by chemical reactions

    5. Rock fracturing

    6. Seawater warming under the sun

  • Hogbom also found three carbon sinks:

    1. Rock weathering (carbon dioxide dissolves in rainwater → reacts with limestone → calcium bicarbonate)

    2. Absorption by plants

    3. Absorption by oceans

  • The first computation climate model was made by Arrhenius, it shows an energy balance model

    • Aimed to test his theory that the ice ages were caused by a drop in CO2

      • Predicted global temperature would rise 5.7C if CO2 is doubled

  • Joseph Fourier realized the two types of heat flow are different

    • Sunlight arrives mainly as visible light

    • Heat leaving the earth is mainly infrared because the earth is not hot enough to radiate visible light

  • Tyndall’s experiments were the first to show clearly that some gases block infra-red heat

    • Found that infra-red heat passes through oxygen and nitrogen easily

    • Ethane, methane, and carbon dioxide all block heat

  • Infra-red rays from each point on the earth radiate in all directions

    • Shallower angle → longer path through the atmosphere

    • When the moon is directly overhead its rays have a shorter path through the atmosphere than when it’s lower in the sky

  • Arrhenius’s model to calculate the effect of different amounts of greenhouse gases has four steps:

    1. Calibrate the equation for known (past) temperatures

    2. Set the “absorption parameter” for a different atmosphere (from lookup tables)

    3. Use the energy balance equation to calculate surface temperature for each grid square

    4. Group results for each latitude and global average

  • The longest running set of measurements of CO2 in the atmosphere were taken at the Mauna Loa observatory in Hawaii

    • The last 50 years of warming is unprecedented

Week Two: What Causes Climate Change?

  • Often times what we feel isn’t actually temperature but heat flow

  • In the atmosphere, greenhouse gases act like styrofoam, slowing heat flow away from the planet

  • Any object that’s warmer than its surroundings gives off rays

    • Wavelength will depend on how hot the object is (hotter the object = shorter the wavelength)

  • The atmosphere is transparent to shortwave radiation from the sun but opaque to (some parts of the infrared rays emitted by the sun

    • The earth’s atmosphere acts as an insulator

      • Heat leaving the planet is slowed down by the greenhouse gases

  • The atmosphere blocks rays on some parts of the spectrum but lets other rays through

  • Greenhouse gas consists of six major substances:

    1. Water

    2. Carbon dioxide

    3. Methane

    4. Ozone

    5. Nitrous oxide

    6. Tri-chloro-fluoro-methane

  • Across five different studies 2024 was found to be the hottest year since recordings began

    • First time the 1.5 C threshold was exceeded

  • The amount of energy received from the sun has changed a little over history → not responsible for warming over the last 50 years

Non-greenhouse gases - have very simple molecules that have very few ways they can vibrate

Greenhouse gases - have complex molecules with molecular bonds that can flex and twist in different directions

  • Gases in the atmosphere the absorb energy at some wavelengths of infrared radiation

  • Greenhouse gases trap outgoing heat from the earth, not heat from the sun

    • Absorb and re-emit energy at specific wavelengths in the infrared spectrum

  • Don’t stop infrared energy from escaping, just slows down the rate it leaves

Radiative forcing - change in the planet’s energy balance due to changes in how the atmosphere absorbs electromagnetic radiation

Keeling Curve - measures the rise in concentration of CO2 since 1960

  • Show that the warming over this period is caused by the rise of greenhouse gases

Climate - average (expected) weather conditions over time for a given region and time of year

Temperature anomalies - changes in average temperature over time against a baseline

Week Three: How Bad Is It?

  • Greenhouse gases act like an insulator, slowing the rate that the heat escapes to space

  • Carbon cycles, CO2 rises through the winter and peaks in late spring

    • Few forests south of the equator → boreal forests of Canada and Russia do most of the work sucking in carbon each summer

  • The PETM was much warmer than today since there was a lot more carbon in the atmosphere

    • Over millions of years the caron was captured by plants and animals → died → carbon was trapped under layers of sediment → pressure turns it into coal and oil

      • If we dig up all the coal and oil and burn it, we’ll return the earth to the PETM conditions (won’t go beyond that)

  • Models don’t predict the future, but rather show what would happen under different scenarios

  • Climate models divide the atmosphere into cubes and track each cube

    • Lakes and clouds are left out of climate models

Albedo - measure of how much the planet reflects sunlight

  • White ice sheets and clouds make the planet “whiter” and increase albedo

  • Dark forests reduce albedo

    • Cutting forests to make farmland → lighter area → reflects more sunlight → negative radiative forcing → cooling effect

Aerosols - tiny particles from industrial pollution that block sunlight → cooling effect

Net zero - condition in which anthropogenic carbon dioxide emissions are balanced by anthropogenic CO2 removals over a specified period

  • Two types of carbon removal

    1. Natural carbon sinks (ex: plants, soil, ocean)

    2. Anthropogenic removals (ex: planting more trees)

  • Until we get to net zero, the amount of carbon in the atmosphere will keep rising, and so will temperatures

  • The only way to stop warming is to go beyond net zero, and to remove carbon from the atmosphere faster than we are adding it

Week Four: Do We Have The Technology To Fix It?

  • The SSPs are complex scenarios for the future that take into account how society will change, with issues of international trade, economic growth, inequality, population, climate policy, economic policy, etc

  • Sustainability is a property of human behaviour

  • Project Drawdown emphasizes that we need to work on reducing sources of GHG emissions and increase existing carbon sinks

  • The relationship between cumulative emissions and temperature is a straight line

  • Under the Paris Agreement, countries had to commit saying what emission cuts they would make (INDC)

    • Every few years they are challenged to make more targets

  • We’re above either of the emission pathways for staying within the UN’s temperature thresholds

    • Also burning through carbon budgets

  • GHG emissions mainly come from electricity + heat production and agriculture + land use (global)

    • Climate solutions needed will vary from region to region

Mitigation - reduction of emissions to mitigate the problem of future warming

Adaptation - changes that allow communities to cope better with the impacts of warming

Solar Radiation Management - directly controls the temperature of the planet by altering the radiative forcing

Week Five: Who Is Affected?

  • Climate change causes oceans to warm → energy to make a hurricane → hurricanes form over warm ocean waters

    • Not clear if climate change will cause more hurricanes, but it will make them bigger

    • Climate change slows down how fast hurricanes move, but increases the wind speed within the hurricane

  • Major consequences of climate change include:

    • More frequent heatwaves

    • Stronger storms and hurricanes

    • Increased drought, forest fires

    • Sea level rise, coastal flooding

    • Ocean acidification

    • Ecosystems wiped out

    • Lower food production

    • Disease and death

    • Poverty and displacement

  • Under climate change there tends to be two effects for any given weather variable

    • Ex: temperature rises and becomes more variable

  • Warming is directly related to cumulative emissions

    • North America and Europe are responsible for half of all historical emissions

  • Countries that are most responsible for causing climate change are the least vulnerable

  • The Bali Declaration on Climate Justice was developed in June 2002, and aimed to redefine climate change in terms of human rights and environmental justice

    • Made of a set of principles to “put a human face” on climate change

    • Consisted of 27 core principles, including rights of people impacted, and measures needed to address climate change

    • Identifies causes of climate change (deforestation, fossil-fuel production and consumption, corporate-led globalization)

    • Identifies who is impacted most (local communities, Indigenous peoples, women, etc)

Week Six: Can We Agree To Fix It?

  • The UN adopted the 2 C threshold in 2009 and added an aspiration to stay below 1.5 C at the Paris agreement in 2015

  • The Paris agreement suggested that sources and sinks of carbon should balance by “the second half of this century” → net zero by 2050

    • Jame Hansen (climate scientist) says we should aim to get back to 350 ppm in the atmosphere (currently at 425 ppm)

  • The UNFCCC set up in 1992, agreed a framework to tackle climate change

    • Brings all 197 member nations together every year for a conference of the parties (COP)

    • Never really worked

  • The Paris agreement was the first big step towards a comprehensive plan for global emissiosn reduction

    • Doesn’t mention key phrases like net-zero, zero emissions, or fossil fuels

    • Paris agreement has started to bend the global stocktake curve downwards

  • There are three main options for climate policy

    1. Market-based mechanisms - preferred by capitalist countries

      • Carbon tax

      • Subsidies

      • Cap-and-trade

      • Clean energy standards

    2. Regulatory instruments

      • Non-tradeable permits

      • Technology and emission standards

      • Produce bans

      • Government investment

    3. Voluntary agreements

  • Canada’s carbon tax doesn’t apply to all provinces and territories

    • Federal scheme consists of two parts:

      1. Price on fuels

        • Applied to fuels based on how much GHGs they produce

      2. Output-based pricing system on companies that produce emissions

        • Fees charged to industrial emitters

        • Allows companies to trade permits with one another if they can’t reduce emissions fast enough to bring down operation costs

    • All revenues are returned to the people

      • Majority of households are better off with the carbon tax

Week Seven: What Will It Cost To Fix It?

  • GDP strongly correlates with carbon emissions

    • Poorer countries have lower emissions per person, while richer countries have higher emissions per person

  • The IPAT equation says that out overall impact is the result of three main factors multiplied together:

    1. Population growth

    2. Affluence

    3. Technology

  • The Kaya identity breaks down consumption into two separate terms:

    1. Dollars we spend (GDP)

    2. Energy we consume in things we spend these dollars on

  • When accounting for carbon emissions they fall into three categories:

    1. Scope 1 - emissions that arise from an organization’s direct activities (buildings and vehicles it operates)

    2. Scope 2 - emissions from purchased energy

    3. Scope 3 - all the emissions that arise elsewhere as a result of the organization’s activities (ex: employee travel)

  • There are two models to “solving” climate change

    1. Ecomodernism - assumes the small amount of decoupling we’ve seen over the last few decades can be ramped up rapidly → can continue to have economic growth while emissions drop

      • Aims to emphasize new technologies without changing the economy

    2. Degrowth - regards economic growth as the problem and looks at how you can have a prosperous society without it

      • Includes things like: redistributing wealth from rich to the poor and universal basic income

  • A sustainable society has three main factors:

    1. Must not harvest a renewable resource faster than it can regenerate

    2. Must not generate waste faster than the environment can absorb them

    3. Must not use non-renewable resources

Neoliberalism - emphasizes the idea that the markets are self-regulating and don’t need government interference

  • Sets economic growth as its primary aim (growth is how the owners of capital can keep making profits)