Discussion 8. Feedback in the Earth System and Impact on Climate Change
EES18
Background: We learned this week that climate change contributes to more intense hurricanes, larger
wildfires, and in many areas, more frequent and damaging landslides and floods.
Feedback in the Earth System plays an important role in determining the amount of warming that occurs
for a given amount of emissions of carbon dioxide from the burning of fossil fuels (gas, oil, coal).
Rules about feedback loops:
1. A positive feedback loop is when an initial change in one element of a loop leads to changes in other
elements that reinforce the initial change (i.e., make it stronger).
2. A negative feedback loop is when an initial change in one element of a loop leads to changes in other
elements that weaken the initial change (i.e., dampen it).
3. Positive feedback loops are destabilizing, and negative feedback loops are stabilizing.
4. Two negative interactions between elements in a control loop cancel each other and make a net
positive interaction.
5. Positive feedback loops will have 0 or an even number of negative interactions; negative feedback
loops will have an odd number of negative interactions. (1, 3, 5, etc.).
Q1. At least two positive feedback loops amplify the warming caused by emissions of fossil fuels. One is
associated with increasing water vapor in the air that in turn traps more heat (water vapor is a greenhouse
gas!). The other is associated with the loss of snow and ice. Draw these feedback loops. The elements in
each loop are described below. Draw an arrow linking each element, define whether the arrow
(interaction) between each set of elements is negative or positive, and label with a Ô or S sign.
a. Air temp, water vapor,
Longwave (LW) heat trapping
b. Air temp, snow and ice, albedo,
energy absorption
Q2. There are negative feedbacks that balance these positive feedbacks and ensure we do not have a
runaway greenhouse effect that continues indefinitely. One important example of such a negative
feedback is the following. The hotter the Earthàsurface gets, the more longwave radiation is emitted
away from the Earth, particularly in deserts. When this radiation escapes into space, it cools Earth.
Please draw this negative feedback loop with two elements: surface temperature and LW radiation
emission.
Q3. Warming may induce carbon cycle feedbacks that keep levels of atmospheric CO2 high for centuries.
One example of such feedback that scientists are concerned with is called permafrost feedback. In this
feedback loop, warming causes frozen permafrost soil to melt, allowing the decomposition of previously
frozen soil organic matter. The decomposition of soil organic matter by microbes releases CO2 back to the
atmosphere, which in turn amplifies warming.
Please draw this positive feedback with 4 elements: CO2, air temp., soil temperature (thaw), and microbial
decomposition:
Q4. Draw one more feedback loop you design that may involve carbon loss from the biosphere with
climate warming. Possible examples include wildfire, loss of trees from drought, etc. Identify and label the
elements of the feedback loop you think are important and then label draw arrows and label the
interactions as positive or negative.

Purchase answer to see full
attachment