10 - feedback within and between the water and carbon cycles ✅

Question 1

what do most natural systems exist in

Answer 1

Most natural systems, unaffected by human activity, exist in a steady-state equilibrium.

They have variable inputs, outputs, flows + stores, but in the long term a broad state of balance is maintained.

Question 2

what is negative feedback

Answer 2

When a system adjusts itself to lessen out or cancel the effect of an initial disruption.

The disruption triggers changes in the system which work in the opposite direction to the initial change.

Equilibrium or balance is maintained because natural systems have internal checks that “put the brakes on” and restore balance.

Question 3

what is positive feedback

Answer 3

These are knock-on effects in natural systems that act to accelerate + amplify any changes that have started after an initial disruption.

When 1 element of a system changes, it upsets the overall equilibrium, leading to changes in other elements.

The system might start to “spin out of control”.

Question 4

how can climate change exemplify positive and negative feedback loops

Answer 4

global warming creates change which slows down warming = POSITIVE FEEDBACK

global warming creates change which speeds up warming = POSITIVE FEEDBACK

Question 5

what are the speculations of feedback within climate

Answer 5

widespread concern among the world’s climate scientists that the positive feedback effects will be far greater than the negative feedback effects in the coming decades.

As a result, there is a significant risk of a high rise in GMST of between 4-6 degrees C by 2100.

Question 6

what is a system threshold

Answer 6

This is a critical limit or level that must not be crossed if accelerated or irreversible changes are to be avoided.

If water or carbon cycles cross their system threshold the equilibrium could potentially be permanently damaged.

Question 7

what is the climates system threshold

Answer 7

Many scientists believe that a global rise in temperatures above 2 degrees C will cross the system threshold for the global carbon cycle and lead to widespread and irreversible changes.

Question 8

what is the effect of thresholds in vegetation

Answer 8

overgrazing of vegetation in an area might lead to desertification as widespread soil erosion follows.

Question 9

what is the effect of a loss of vegetation

Answer 9

Irreversible loss of vegetation will cross the system threshold for both the water and carbon cycles, leading to permanent changes.

Question 10

what are difficulties with predicting likely changes of climate change

Answer 10

• Pooling global data
• Identifying short term changes or long term trends
• Limited/unreliable historical evidence (proxy, instrumental records)
• Natural processes are highly interconnected
• Timescales of changes
• Gaps in atmospheric understanding

Question 11

how will permafrost be effected

Answer 11

• Significant (1672 Pg) organic carbon is estimated to be stored in the Arctic permafrost regions of the Northern Hemisphere.
• This is 50% of the Earth’s carbon that is stored in below ground pools.
• As the Arctic temperatures increase the extent of the permafrost declines releasing the stored carbon to the atmosphere.
• The more is released, the more it warmers, the more melts! Feedback!
• However, some modelling suggest a certain amount of increased SINK - rising temperatures increase the length of the growing season and bring more productive vegetation to northern latitudes

Question 12

what is the purpose of feedback

Answer 12

• Negative feedback between water and carbon cycles helps an equilibrium + balance to be maintained/restored.
• Positive feedback between water and carbon cycles may accelerate the rate of change beyond a “tipping point” of no return.

Question 13

what is evidence of feedback in the cryosphere

Answer 13

• Ice has a high albedo + reflects 4/5 of all incoming solar radiation.
• As temperatures rise, the loss of ice cover exposes more dark surfaces and the warming of the atmosphere is accelerated.
• Even a small change in sea ice coverage triggers a positive feedback, leading to accelerated global warming.

Question 14

is positive or negative feedback in the cryosphere significant

Answer 14

Most scientists believe that positive feedback will result from ice melting.

However, there is an alternative argument that negative feedback could occur as more clouds are created with a high albedo

Question 15

how is methane stored

Answer 15

Methane is a powerful greenhouse gas and huge volumes are stored in permafrost regions.

Question 16

what is the importance of permafrost

Answer 16

• About ¼ of the Earth’s surface is affected by continuous or sporadic permafrost in the tundra, polar + mountain regions.
• Permafrost covers 23 million square kilometres, forming in glacial periods, with most surviving 10,000 years in the Holocene era.

Question 17

what is the biggest threat to permafrost

Answer 17

• According to NASA, temperatures in Newtok, Alaska have risen by 4 degrees C since 1960 and by as much as 10 degrees C in winter months.
• This is leading to a rapid melting of permafrost at a rate not witnessed in human history.
• This is creating concerning positive feedback.

Question 18

what is the methane positive feedback loop

Answer 18

As the atmosphere warms, more permafrost is expected to melt.
Large amounts of methane are released.
The atmosphere warms up quicker.
Even more methane is released…

Question 19

what is the marine carbon feedback loop

Answer 19

• Increasing temperatures will lead to more evaporation.
• This might lead to a positive feedback loop where water vapour, as a greenhouse gas, traps more heat.
• However, it is also possible that a negative feedback loop will be created as water vapour forms more clouds, increasing the albedo in the atmosphere.

Question 20

what is the positive feedback in marine carbon

Answer 20

A reduction in the ability of oceans to absorb surplus CO2 from the atmosphere (as warm water is less effective than cold water) could lead to a positive feedback within the atmospheric carbon cycle.

Question 21

what is the effect of ocean acidification

Answer 21

Ocean acidification could create a positive feedback on the biological pump, impacting negatively on coral + marine ecosystems.

Question 22

what are the new IPCC future pathways

Answer 22

Due to the current debate and uncertainty, the fifth IPCC climate change findings has a range of nearly 4 degrees C difference by the year 2100.

Question 23

how is the water supply being affected

Answer 23

• There are potentially huge implications of the loss of cryospheric ice upon water security.
• One quarter of the global population relies upon Himalayan meltwater, predominantly in China and India.
• In the short term meltwater levels will rise, but when the glaciers are lost a critical water supply will be gone.