ENV 101 - Module 1

Planetary boundaries and changing climate. Lectures 1-7

Planetary Boundaries

Safe operating spaces for the Earth to maintain the Holocene epoch.

Number of planetary boundaries

9

What are the planetary boundaries?

Climate change

Ocean acidification

Stratospheric ocean depletion

Biogeochemical fluxes (N and P)

Freshwater use

Biosphere integrity

Change in land use

Atmospheric aerosol loading

Novel entities

Holocene

Current geological epoch. Has certain climatic features that are fundamental for life, including human life.

Climate change

The warming of the planet and increased variability in the climate. Climate is a major driver of the Earth system.

Ocean acidification

Oceans dissolve CO2 from the atmosphere leading to the formation of carbonic acid. Average ocean pH has dropped by 0.1.

Stratospheric ozone depletion

CFCs created a hole in the ozone layer in the atmosphere. Since being phased out, the ozone layer had begun to recover.

Biogeochemical fluxes

Stores and fluxes of nitrogen and phosphorus have been altered, e.g. due to use of chemical fertilisers and runoff.

Freshwater use

Humans use more than 50% of the Earth’s freshwater and accessible runoff - 70% of this is for agriculture.

Which areas have the most water scarcity?

South/east Asia, Africa, Middle East, Caribbean

Biosphere integrity

Refers to the extinction rate, which is currently 100x greater than the ‘background rate’.

Change in land use

Human activity has transformed just over 50% of the Earth’s surface, due to agriculture, urbanisation, etc.

Atmospheric aerosol loading

Global aerosol concentrations have doubled since the 1800s. This is mostly black carbon from combustion.

Novel entities

Humans are creating, producing, and releasing chemicals at a pace greater than that for assessment and monitoring.

Doughnut economy model

Combines planetary boundaries with social boundaries, such as healthcare, education, justice.

Matauranga Maori model

Whakapapa, Kaitiaki, Mauri

Sustainable Development Goals (SDGs)

17 goals created by the UN to end poverty, reduce inequality, and build more peaceful and prosperous societies.

One Health Concept

Combines the health of people, animals, and the environment into a single model. Based on health sciences, but also looks at social, political, and economic factors.

Climate

A description of weather variables over a long period of time. Variables include temperature, precipitation, wind, humidity, etc.

How many years of data is required to determine the climate of a place?

30

What do weather variables depend on?

Flow of energy between the atmosphere, ocean, and land.

Energy

The ability to do work.

Electromagnetic waves

The form of energy that travels through space and Earth’s atmosphere to drive the climate.

Wavelength

The distance for one full cycle of a wave.

Composition of radiation from the Sun

44% visible light, 49% infrared, 7% ultraviolet

Infrared

Thermal radiation. Longer wavelength than visible light

Ultraviolet

Shorter wavelength than visible light

Watt

Unit for energy flux/rate of energy

W/m²

Unit for energy flux density/rate of energy over area

Insolation

Incoming solar radiation. 

Energy flux density over Earth from the Sun

340W/m²

Atmospheric scattering

An interaction between the insolation and atmosphere. A different relative angle between the source of the radiation (the Sun) and the observer causes different colours of light to be seen.

How does the atmosphere impact the insolation?

Atmospheric scattering, reflection, absorption and re-emission

Albedo

The proportion of insolation that is reflected from a surface.

Ocean has ____ albedo

low

Poles have ____ albedo

high

Deserts have ____ albedo

high

Forests have ____ albedo

low

Snow has ____ albedo

high

Where is albedo lowest?

Bodies of water.

Where is albedo highest?

Snowy regions and deserts.

Clouds have ____ albedo

high

What type of radiation is reflected at the surface?

Thermal radiation

What kind of gases interact with thermal radiation?

Greenhouse gases (GHGs)

Greenhouse gases

Gases that make up a small proportion of the atmosphere, but are heavy and interact with thermal radiation, trapping heat. These include water vapour, CO2, methane, ozone, N2O, and CFCs

CFCs

Chlorofluorocarbons. Freon-11 = CCl3F, Freon-12 = CCl2F2

Why do larger molecules act as greenhouse gases?

They are more complex and can interact with a larger range of wavelengths of thermal radiation.

Global energy budget

Where all the different types of energy go (absorbed, reflected, etc).

Latent heat

Energy required to change liquid water to water vapour, which causes a cooling effect. 

Sensible heat

Heat moved by turbulent motion in the air. This causes a transfer of heat between the surface and atmosphere.

Ground heat

Heat movement in and out of the ground - absorbed during the day and released at night. This has a net zero effect over the course of a day

How much is the global energy imbalance?

1W/m²

Where does the imbalance in energy go?

It is absorbed by the oceans.

How does insolation vary and move around the Earth?

It varies with latitude, with more at the equator and less at the poles. This means that it moves from the equator towards the poles.

Seasonal change in insolation

Due to changes in the Earth’s tilt, the amount of insolation varies across the surface of the Earth.

Planetary albedo

30%

Composition of planetary albedo

20% clouds, 6% atmosphere, 4% surface

How much radiation is not reflected or absorbed at the surface?

100W/m²

What has been used to create a proxy record for Earth’s climate?

Fossil records, deep-sea sediment cores, oxygen isotopes. 

Eocene

Warmest period in Earth’s history. 

What was the average temperature in the Eocene?

28 degrees

What was the average deep-sea temperature in the Eocene?

16 degrees

What were the atmospheric CO2 levels during the Eocene?

500-1000ppm

What caused the decline in temperature following the Eocene?

Reduction in atmospheric CO2 due to declining volcanic activity and seafloor spreading and increased weathering.

Pleistocene

The last period of glacial-interglacial cycles.

Milankovitch cycles

Small variations in solar radiation levels due to variations in Earth’s orbit and tilt.

What were the atmospheric CO2 levels during the last glacial maximum?

180ppm

When did the Holocene begin?

Around 10,000 years ago.

What were the atmospheric CO2 levels during the interglacial periods of the Pleistocene?

300ppm

When was the Medieval Warm Period?

950-1250CE

When was the Little Ice Age?

1500-1800CE

Sunspot cycles

11 year cycles where the amount of solar radiation fluctuates due to the appearance and disappearance of sunspots.

How much has the average global temperature changed over the last 150 years?

+1 degree

What are the factors leading to the recent temperature increase?

Land use change, atmospheric aerosols, greenhouse gases.

How long does CO2 last in the atmosphere?

100 years

How long does methane last in the atmosphere?

12 years

What happens to methane after 12 years in the atmosphere?

It breaks down into CO2.

What are the atmospheric CO2 levels today?

420ppm

Ocean-atmosphere interaction

The exchange of heat, temperature, aerosol, gas, and momentum between the atmosphere and ocean.

Teleconnection

Relationship between climate variables at the equator and other parts of the world.

How much of the ocean interacts with the atmosphere?

The top 50m.

How much of the Earth’s surface does ocean cover?

70%

What is the average depth of the ocean?

4km

El Nino Southern Oscillation (ENSO)

Ocean-atmosphere interaction that causes temperatue fluctuations across the Pacific ocean and changes global weather patterns.

How long is the ENSO cycle?

2-10 years

What are the 3 states of ENSO?

Normal/neutral state, El Nino, La Nina

Normal/neutral state

Trade winds blow east-to-west along the Pacific equator. Warm water piles up on the western side, and upwelling results in more nutrients in the cold water on the eastern side.

What is the climate like in the western Pacific during the normal/neutral state?

Wetter

What is the climate like in the eastern Pacific during the normal/neutral state?

Drier

El Nino

Trade winds weaken or even reverse, so warm water remains on the eastern side.

What is the climate like in the western Pacific during El Nino?

Drier

What is the climate like in the eastern Pacific during El Nino?

Wetter

What is the climate like in New Zealand during El Nino?

There is a high to the north, southwesterly winds, and typically wetter in the west than the east.

La Nina

Trade winds strengthen, so waters in the western Pacific are warmer and deeper than usual.

What is the climate like in the western Pacific during La Nina?

Wetter

What is the climate like in the eastern Pacific during La Nina?

Drier

What is the climate like in New Zealand during La Nina?

A high over the South Island, northeast winds, more rain in the north/east of the North Island and dry in the south/southwest of the South Island.

How does ENSO affect weather predictability?

Weather tends to be more predictable during El Nino and La Nina than during the normal/neutral state.

What happens to global temperatures during La Nina?

Cooling

What happens to global temperatures during El Nino?

Warming