Climate Feedbacks and the Carbon Budget

Question 1

How does positive and negative feedback typically affect systems

Answer 1

Positive feedback amplifies system changes and tends to destabilize the system; negative feedback inhibits system changes and tends to stabilize the system.

Question 2

What is Climate Feedback?

Answer 2

Climate feedback

A process that either amplifies or reduces a climatic trend toward either warming or cooling.

Question 3

What is ice-albedo feedback?

Answer 3

This feedback arises from the simple fact that ice is more reflective (that is, has a higher albedo) than land or water surfaces. Therefore, as global ice cover decreases, the reflectivity of Earth’s surface decreases, more incoming solar radiation is absorbed by the surface, and the surface warms.

This is an example of positive feedback.

Question 4

What is the carbon cycle?

Answer 4

Many climate feedbacks involve the movement of carbon through Earth systems and the balance of carbon over time within these systems. The carbon on Earth cycles through atmospheric, oceanic, terrestrial, and living systems in a biogeochemical cycle known as the carbon cycle

Question 5

What are carbon sources?

Answer 5

Areas of carbon release are carbon sources

Question 6

What is a carbon sink/reservoir?

Answer 6

Carbon sink
An area in Earth’s atmosphere, hydrosphere, lithosphere, or biosphere where carbon is stored; also called a carbon reservoir

Question 7

What is the global carbon budget?

Answer 7

Global carbon budget (11)
The exchange of carbon between sources and sinks in Earth’s atmosphere, hydrosphere, lithosphere, and biosphere.

The overall exchange of carbon between the different systems on Earth is the global carbon budget, which should naturally remain balanced as carbon moves between sources and sinks

Question 8

What are some important carbon sinks?

Answer 8

• The ocean is a major carbon storage area, taking up CO2 by chemical processes as it dissolves in seawater and by biological processes through photosynthesis in microscopic marine organisms called phytoplankton.
• Rocks, another carbon sink, contain “ancient” carbon from dead organic matter that was solidified by heat and pressure, including the shells of ancient marine organisms that lithified to become limestone
• Forests and soils, where carbon is stored in both living and dead organic matter
• The atmosphere is perhaps the most critical area of carbon storage today, as human activities cause emissions that lead to increasing concentrations of CO2 into the atmosphere

Question 9

What are some ways that humans have impacted the Carbon Budget?

Answer 9

• Clearing of forests for agriculture, which reduces the areal extent of one of Earth’s natural carbon sinks (forests) and transfers carbon to the atmosphere.
• The burning of fossil fuels became a large source of atmospheric CO2 and began the depletion of fossilized carbon stored in rock These activities have transferred solid carbon stored in plants and rock to gaseous carbon in the atmosphere.

Question 10

What is ocean acidification?

Answer 10

Studies suggest that uptake of carbon by the oceans is offsetting some of the atmospheric increase. When dissolved CO2 mixes with seawater, carbonic acid (H2CO3) forms, in a process of ocean acidification.

Question 11

What are the consequences of the ocean absorbing the rising concentrations of atmospheric carbon?

Answer 11

Scientists estimate that the oceans have absorbed some 28% of the rising concentrations of atmospheric carbon, slowing the warming of the atmosphere. However, as the oceans increase in temperature, their ability to dissolve CO2 is lessened. Thus, as global air and ocean temperatures warm, more CO2 will likely remain in the atmosphere, with related impacts on Earth’s climate.

Question 12

How is the uptake of excess carbon effecting earth’s terrestrial environment?

Answer 12

Uptake of excess carbon is also occurring in Earth’s terrestrial environment, as increased CO2 levels in the atmosphere enhance photosynthesis in plants. Research suggests that this produces a “greening” effect as plants produce more leaves in some regions of the world

Question 13

What is the permafrost-carbon feedback?

Answer 13

For example, the permafrost–carbon feedback is now underway in the Arctic. This process occurs as warming temperatures thaw permafrost, and eventually leads to a greater amount of carbon emitted to the atmosphere rather than stored in the ground that accelerating warming

Question 14

What is the most abundant natural greenhouse gas?

Answer 14

Water vapour is the most abundant natural greenhouse gas in the Earth–atmosphere system.

Question 15

What is the water vapor feedback? Is it a positive or negative feedback?

Answer 15

Water vapour feedback is a function of the effect of air temperature on the amount of water vapour that air can absorb, a subject discussed in Chapters 7 and 8. As air temperature rises, evaporation increases because the capacity to absorb water vapour is greater for warm air than for cooler air. Thus, more water enters the atmosphere from land and ocean surfaces, humidity increases, and greenhouse warming accelerates. As temperatures increase further, more water vapour enters the atmosphere, greenhouse warming further increases, and the positive feedback continues.

Question 16

How can the cloud formation of increased water vapour affect earths climate?

Answer 16

As atmospheric water vapour increases, higher rates of condensation will lead to more cloud formation. Remember from Chapter 4 (Figure 4.8) that low, thick cloud cover increases the albedo of the atmosphere and has a cooling effect on Earth (cloud albedo forcing). In contrast, the effect of high, thin clouds can cause warming (called cloud greenhouse forcing).

Question 17

What is a carbon climate feedback?

How can we explain the slight lag time between CO2 and methane concentrations and temperature trends?

Answer 17

We saw earlier that over long time periods, CO2 and methane concentrations track temperature trends, with a slight lag time (Figure 11.11). One hypothesis for this relationship is that warming temperatures caused by changes in Earth’s orbital configuration may trigger the release of greenhouse gases (both CO2 and methane), which then act as a positive feedback mechanism: Initial warming leads to increases in gas concentrations; elevated gas concentrations then amplify warming; and so on.

Question 18

Describe the main points of the CO2 weathering feedback.

Answer 18

• increasing CO2 stored in the atmosphere increases global warming, which increases the amount of water vapor present in the atmosphere (warm air masses absorb more moisture).
• Greater atmospheric moisture in a warmer climate generally leads to greater precipitation. With increasing rainfall comes an increase in the breakdown of exposed rock on Earth’s surface by chemical weathering processes
• This process occurs over long time periods as CO2 in the atmosphere dissolves in rainwater to form a weak acid (carbonic acid, H2CO3), which then falls to the ground and works to chemically break down rocks.
• The outputs of this weathering, consisting of chemical compounds dissolved in water, are carried into rivers and eventually oceans, where they are stored for hundreds of thousands of years in seawater, marine sediments, or corals.
• The result is that, over long time periods, CO2 is removed from the atmosphere and transferred to the ocean carbon sink. This creates negative climate feedback because the overall effect is to reduce the global warming trend.