Natural Drivers of Climate Change

PQS7.1. CONTRAST forcings and feedbacks on the climate system

Forcing processes of Earth’s surface temperature

an increase in solar irradiance

an increase in volcanic activity

an increase in the number of sunspots

an increase in the size of continental land masses

PQS7.1. CONTRAST forcings and feedbacks on the climate system

Feedback loop processes involving Earth’s surface temperature

An increase in boreal forest area.

An increase in sea ice cover

High Clouds

• Net warming effect

• Ice crystals

Less effective at reflecting solar radiation (lower albedo than low clouds)

Their effective radiating temp is much colder than that of Earth’s surface → Efficient at absorbing heat from Earth’s surface→ greenhouse contribution is large

• With climate change:

  → atmosphere warms,

  → tropopause height increases

  → high clouds rise higher

  → greenhouse effect increases

  → warm the planet

• low clouds

-thick

-effective at reflecting solar radiation → high albedo

-because they are low→ effective radiating temp is not different from that of Earth’s surface → greenhouse contribution is smaller than for high clouds.

With climate change:

→ fewer lower clouds in subtropics due to intensification of the Hadley Cell

→ fewer low clouds→ less cooling effect

→ Earth warms more

Forcing

An imposed change that triggers a change in climate change. I.e. the change is not dependent on the climate system response.

Forcing initiates the feedback.

Feedback

A change that results from the response of the climate system to an imposed change. I.e. the change is a next step change in X response to an initial change in X.

The feedback determines the amplitude of the change.

PQS7.2. CONTRAST forcings and feedbacks on the climate system

The increase in atmospheric from fossil fuel burning has a direct warming effect on climate by absorbing, then re-emitting, infrared radiation emitted by the Earth’s surface. This warming induces other environmental changes that further enhance warming (we call them amplifying feedbacks). Which of the following effects resulting from warming can be viewed as feedback mechanisms that amplify warming resulting from the increase in atmospheric ? Choose all that apply.

increasing the water vapor content of the atmosphere

decreasing snowfall

decreasing ice cover

PQS7.3. DESCRIBE the long-term evolution of solar radiation and its potential effect on Earth’s mean temperature

TRUE OR FALSE

If everything else (albedo, greenhouse gases) stays constant, increasing the solar constant would result in a higher temperature on Earth.

The “solar constant” refers to the flux of solar energy per square metre intercepted by the Earth’s cross-section.

TRUE

If everything else (albedo, greenhouse gases) stays constant, increasing the solar constant would result in a higher temperature on Earth.

The “solar constant” refers to the flux of solar energy per square metre intercepted by the Earth’s cross-section.

The “solar constant” of Earth is determined by the Sun’s temperature and size and by the distance between the Sun and Earth.

PQS7.3. DESCRIBE the long-term evolution of solar radiation and its potential effect on Earth’s mean temperature

TRUE OR FALSE

The “solar constant” refers to the flux of solar energy per square metre reaching the Earth’s upper atmosphere on average, taking into account that solar energy is distributed over the surface area of the upper atmosphere owing the Earth`s rotation.

FALSE

The “solar constant” refers to the flux of solar energy per square metre reaching the Earth’s upper atmosphere on average, taking into account that solar energy is distributed over the surface area of the upper atmosphere owing the Earth`s rotation.

PQS7.4. DESCRIBE the long-term evolution of solar radiation and its potential effect on Earth’s mean temperature

TRUE OR FALSE

The Sun is getting brighter with age because of nuclear reactions in the Sun’s interior that convert helium into hydrogen.

FALSE

The Sun is getting brighter with age because of nuclear reactions in the Sun’s interior that convert helium into hydrogen.

PQS7.4. DESCRIBE the long-term evolution of solar radiation and its potential effect on Earth’s mean temperature

TRUE OR FALSE

The intensity of radiation emitted by the Sun has gradually increased since the formation of the solar system.

We find evidence for liquid water and living organisms prior to 1.8 billion years ago.

With modern-day concentrations of atmospheric greenhouse gases and modern-day albedo, the early Earth’s surface would have been frozen prior to 1.8 billion years ago.

TRUE

The intensity of radiation emitted by the Sun has gradually increased since the formation of the solar system.

We find evidence for liquid water and living organisms prior to 1.8 billion years ago.

With modern-day concentrations of atmospheric greenhouse gases and modern-day albedo, the early Earth’s surface would have been frozen prior to 1.8 billion years ago.

Faint Young Sun Paradox

the contradiction between geological evidence of liquid water (and life) on early Earth and astrophysical models showing the Sun was ~30% less luminous 3.5–4 billion years ago.

The concentration of greenhouse gases in the early atmosphere was higher than today.

Faint Young Sun Paradox

Early in Earth’s history, lower energy from the then-fainter Sun would not have been enough to keep Earth’s temperature in the range of liquid water, yet there is early evidence for liquid water.

PQS7.7. EXPLAIN the feedback mechanism believed to have maintained Earth's average temperature within the range of liquid water over 100s of millions of years as the Sun got brighter

The Sun is still getting brighter. A billion years into the future, how do you think greenhouse gas concentrations will compare to today (think only of long-term, natural processes)?

Greenhouse gas concentrations will be lower than today.

PQS7.8. EXPLAIN the feedback mechanism believed to have maintained Earth's average temperature within the range of liquid water over 100s of millions of years as the Sun got brighter

A stabilizing feedback loop stabilizes atmospheric concentrations on multi-million year timescales because…

higher atmospheric increases the acidity of rain water, the reaction rate between carbonic acid and silicate minerals, and the removal rate of atmospheric by weathering.

Imagine a planet like ours, on which, over a long period of time, the area covered by continents grew larger and larger. How would you expect this trend to influence the planet’s climate?

The planet’s temperature would cool because more area would be available for chemical weathering.

PQS7.10. EXPLAIN the feedback mechanism believed to have maintained Earth's average temperature within the range of liquid water over 100s of millions of years as the Sun got brighter

As the Sun’s radiation increases → temperature on Earth INCREASES/DECREASES → weathering rates and CO2 uptake INCREASES/DECREASES → atmospheric CO2 INCREASES/DECREASES → greenhouse warming INCREASES/DECREASES, compensating for the higher solar radiation.

As the Sun’s radiation increases → temperature on Earth INCREASES/DECREASES → weathering rates and CO2 uptake INCREASES/DECREASES → atmospheric CO2 INCREASES/DECREASES → greenhouse warming INCREASES/DECREASES, compensating for the higher solar radiation.

PQS7.11. EXPLAIN the effect of tectonic activity on the long term evolution of greenhouse gas concentrations

Enhanced mountain building causes

an increase in weathering, and therefore a decrease in atmospheric .

EXPLAIN the effect of tectonic activity on the long term evolution of greenhouse gas concentrations

Enhanced tectonic activity causes

an increase in volcanism that will slowly be compensated by an increase in weathering, so that atmospheric increases first, and then stabilizes at a higher value.

EXPLAIN the effect of tectonic activity on the long term evolution of greenhouse gas concentrations

Tectonic activity suddently slows down, reducing the rate of volcanism. What happens next?

Atmospheric CO starts to ____ .

(a)

increase

(b)

does not change

(c)

decrease

As a consequence, atmospheric temperature _____ .

(a)

does not change

(b)

decreases

(c)

increases

As a consequence, the rate of silicate weathering ____ .

(a)

does not change

(b)

increases

(c)

decreases

When will the rate of silicate weathering stabilise?

(a)

When the atmospheric CO2 concentration is zero.

(b)

When it matches the rate of volcanism.

(c)

When it reaches a level lower than the initial rate.

(d)

When it reaches a level higher than the initial rate.

How does the final atomospheric CO concentration compare to the CO concentration before the perturbation?

(a)

It is the same.

(b)

It is higher.

(c)

It is lower.

What is the planet's new mean surface temperature, compared to before the perurbation?

(a)

It is higher than before.

(b)

It is lower than before.

(c)

It is the same as before.

Tectonic activity suddently slows down, reducing the rate of volcanism. What happens next?

Atmospheric CO starts to decrease.

As a consequence, atmospheric temperature _____ .

decreases

As a consequence, the rate of silicate weathering decreases.

When will the rate of silicate weathering stabilise?

When it matches the rate of volcanism.

How does the final atomospheric CO concentration compare to the CO concentration before the perturbation?It is lower.

What is the planet's new mean surface temperature, compared to before the perurbation?

It is lower than before.

Tectonic activity moves continents to a lower latitude, where it is warmer. As a result, silicate weathering becomes more effective, and the weathing rate increases. What happens next?

Atmospheric CO starts to ____ .

As a consequence, atmospheric temperature _____ .

As a consequence, the rate of silicate weathering ____ .

When will the rate of silicate weathering stabilize?

How does the final atomospheric CO2 concentration compare to the CO2 concentration before the perturbation?

What is the planet's new mean surface temperature, compared to before the perurbation?

Tectonic activity moves continents to a lower latitude, where it is warmer. As a result, silicate weathering becomes more effective, and the weathing rate increases. What happens next?

Atmospheric CO starts to decrease.

As a consequence, atmospheric temperature decrease.

As a consequence, the rate of silicate weathering decreases.

When will the rate of silicate weathering stabilize?

When it matches the rate of volcanism.

How does the final atomospheric CO2 concentration compare to the CO2 concentration before the perturbation?

It’s lower.

What is the planet's new mean surface temperature, compared to before the perurbation?

It’s lower than before.

PQS7.14. EXPLAIN the effect of tectonic activity on the long-term evolution of greenhouse gas concentrations

Consider a future time in Earth’s history, when the Pacific Ocean basin closes and North America and Asia are about to collide. What might you expect for Earth’s climate following that collision?

Earth’s climate will cool after that time, because the collision will increase chemical weathering and draw out of the atmosphere.

PQS7.15. EXPLAIN the effect of tectonic activity on the long-term evolution of greenhouse gas concentrations

Mountain ranges formed when two continental plates collide…

Mountain ranges formed when two continental plates collide, decrease atmospheric by increasing the removal of carbon from the atmosphere by weathering because mountain building increases the surface area of rock in contact with rain water.

PQS7.16. COMPARE the relative importance of the radiative forcing from shorter-term changes in solar radiation (sunspots), and volcanic activity, and their potential effect on Earth’s mean temperature

On short, one-to-two-year timescales, volcanic activity

On short, one-to-two-year timescales, volcanic activity cools the Earth, because of the emission of sulfate aerosols.
These aerosols:

• Reflect incoming solar radiation

• Increase Earth’s albedo

• Reduce the amount of sunlight reaching the surface

EXPLAIN the effect of seafloor spreading and continental drift on the long-term evolution of the Earths albedo and its impact on the long-term evolution of climate

During the most geologically-recent ice ages (the most recent “glacial maximum” was 20,000 years ago), sea level was about 120 m lower. How would this affect Earth’s albedo?

Due to lower sea level, albedo during the ice ages would have been higher than today, adding to the cooling from reflective ice sheets.

PQS7.18. EXPLAIN the effect of seafloor spreading and continental drift on the long-term evolution of the Earths albedo and its impact on the long-term evolution of climate

Higher sea level…

decreases the albedo of the Earth’s surface.

EXPLAIN the effect of seafloor spreading and continental drift on the long-term evolution of the Earths albedo and its impact on the long-term evolution of climate

The albedo of the Earth’s surface tends to be higher

when land masses are________ continents.

This is because the formation of large continents promotes the expansion of _______

The albedo of the Earth’s surface tends to be higher

when land masses are amalgamated in few large continents.

This is because the formation of large continents promotes the expansion of deserts.

PQS7.20. EXPLAIN the effect of seafloor spreading and continental drift on the long-term evolution of the Earths albedo and its impact on the long-term evolution of climate

Tectonic activity with slow seafloor spreading rate causes thin/thick mid ocean ridges. This cause higher/cooler sea level, which in turn results in higher/lower albedo and causes cooling/ warming.

Tectonic activity with slow seafloor spreading rate causes thin/thick mid ocean ridges. This cause higher/lower sea level, which in turn results in higher/lower albedo and causes cooling/ warming.

EXPLAIN the effect of seafloor spreading and continental drift on the long-term evolution of the Earths albedo and its impact on the long-term evolution of climate

The albedo of the Earth’s surface tends to be lower

when continents that are located closer to the                                   Equator/ poles.       

This is because continents located near the poles are…

The albedo of the Earth’s surface tends to be lower

when continents that are located closer to the                                   Equator/ poles.       

This is because continents located near the poles are a prerequisite to producing continental ice sheets but does not guarantee that ice sheets will form.

The albedo of the Earth’s surface tends to be higher when continents that are located closer to the Equator/ poles.

This is because continents located near the poles are…

The albedo of the Earth’s surface tends to be higher when continents that are located closer to the Equator/ poles.

This is because continents located near the poles are…a prerequisite to producing continental ice sheets but does not guarantee that ice sheets will form.

PQS7.22. DESCRIBE how different types of clouds affect Earths climate differently

Cirrus are low/high altitude clouds consisting of ice crystals/water droplets that warm/cool Earth’s surface.

Cirrus are low/high altitude clouds consisting of ice crystals/water droplets that warm/cool Earth’s surface.

DESCRIBE how different types of clouds affect Earths climate differently

Cirrus are high/low altitude clouds consisting of … that warm/cool the Earth’s surface.

Cirrus are high altitude clouds consisting of ice crystals that warm the Earth’s surface.

Stratus are high/ low altitude clouds consisting of water droplets/ice crystals that warm/cool the Earth’s surface.

Stratus are low altitude clouds consisting of water droplets that cool the Earth’s surface.

DESCRIBE how different types of clouds affect Earths climate differently

TRUE OR FALSE

The mean temperature of a planet increases as its albedo increases.

The oceans are the most important contributor to the Earth’s albedo.

Clouds are smaller contributors to the Earth’s albedo than deserts.

The albedo of a planet is the fraction of sunlight absorbed by the planet.

FALSE

The mean temperature of a planet increases as its albedo increases.

The oceans are the most important contributor to the Earth’s albedo.

Clouds are smaller contributors to the Earth’s albedo than deserts.

The albedo of a planet is the fraction of sunlight absorbed by the planet.

DESCRIBE how different types of clouds affect Earths climate differently

TRUE OR FALSE

The albedo of a planet is the fraction of sunlight reflected to outer space by the planet.

TRUE

The albedo of a planet is the fraction of sunlight reflected to outer space by the planet.

DESCRIBE how different types of clouds affect Earths climate differently

With climate change, high clouds are predicted to be higher in the atmosphere. How is this going to affect their warming/cooling effect and why?

Clouds will warm the planet more, because they will be even colder than Earth's surface.

DESCRIBE how different types of clouds affect Earths climate differently

With climate change, polar low clouds will have more liquid (rather than ice) content. How will this affect their warming/cooling effect on Earth's surface and why?

They will cool the surface more, because liquid clouds are thicker and more reflective.

DESCRIBE the amplifying feedback between ice cover and climate

If temperature decreased due to an external forcing such that an ice sheet started to grow on Canada, what would the presence of the ice sheet do to Earth’s temperature?

Amplify the cooling and make it even colder.

DESCRIBE the amplifying feedback between ice cover and climate

Create a sequence that correctly describes an amplifying climatic feedback involving changes in the albedo of the Earth's surface:

Climate warming → expansion of tundra/forest →

decreased/increased winter albedo further warming/cooling.

Climate warming → expansion of tundra/forest →

decreased/increased winter albedo further warming/cooling.

DESCRIBE the effect of changes in vegetation cover and associated feedbacks on albedo

If spruce forest expands into the tundra as Earth’s temperature warms, what would this do to Earth’s temperature?

Amplify the warming and make it even warmer, because forests have a lower albedo than tundra.

DESCRIBE the effect of changes in vegetation cover and associated feedbacks on albedo

At times in Earth’s history when there have been just a few large continents, how has Earth's albedo changed?

Albedo is higher, because there are more deserts in the middle of large continents.