Task 4: Climate Change

Question 1

What is radiative forcing?​

Answer 1

​

The change in the balance between the energy Earth receives from the Sun and the energy Earth radiates back into space, caused by changes in external factors (such as CO₂ levels or solar output)​

Imbalance of incoming and outgoing energy​

It is measured in watts per square meter (W/m²) and represents the energy imbalance in the Earth’s climate system​

Question 2

What is radiative balancing?​

Answer 2

Radiative Balance:​

The state where the energy Earth receives from the Sun incoming energy (IE) is equal to the energy Earth radiates back into space outgoing energy (OE)​

Simplified Explanation: ​

It’s like balancing a budget—if you receive as much energy as you spend, the climate stays stable​

Question 3

What is positive and negative radiative forcing?​

Answer 3

Positive radiative forcing is when the imbalance of incoming and outgoing energy causes an increase in temperatures on earth due to more incoming than outgoing energy ​

Incoming energy> outgoing energy​

Negative radiative forcing is when the imbalance of incoming and outgoing energy causes a decrease in temperatures on earth due to a greater outgoing energy than incoming energy​

Incoming energy< outgoing energy ​

Question 4

What are natural and anthropogenic drivers of positive radiative forcing?​

Answer 4

Natural drivers of positive radiative forcing​:
- Solar insolation​

Anthropogenic drivers of positive radiative forcing​:
- Burning of fossil fuels
- Livestock​ emissions

Question 5

What are natural and anthropogenic drivers of negative radiative forcing?​

Answer 5

Natural drivers of negative radiative forcing​: Volcanic eruptions (aerosols – enhancing albedo)​

Anthropogenic drivers of negative radiative forcing​: Land use change (deforestation – enhancing albedo)​

Question 6

Why is the concept of radiative forcing important for understanding climate change?​

Answer 6

It is important in understanding climate change, because it explains changes in climate by explaining imbalances between incoming and outgoing energy that can either warm or cool the earth surface temperature​.

Question 7

What would happen to the energy flows if we would add more GHG in the atmosphere(short and long term)?​

Answer 7

Short term​: Imbalance of energy flows causing positive radiative forcing. The heat from earth’s surface can not escape to space because of the increase of GHG absorbing all of the heat and re- emmiting it to the surface​

Long term : After imbalance of energy flows an equilibrium will be reached with higher temperatures​

Question 8

What are greenhouse gasses?​

Answer 8

Greenhouse gases are gases on the earth’s atmosphere that can trap heat​. They let in incoming solar radiation (short wave) and absorb infrared radiation (long wave)​, and re-emit infrared energy (heat) back to Earth’s surface as downwelling.

Question 9

What is the greenhouse effect?​

Answer 9

The natural greenhouse effect occurs when greenhouse gasses in the atmosphere absorb infrared(long waved) radiation and re emit this to earth’s surface​. Heating up the earth’s surface and causing a positive radiative forcing​

Question 10

What are Climate Feedbacks?​

Answer 10

Climate Feedback is an interaction in which a perturbation in one climate quantity causes a change in a second, and the change in the second quantity ultimately leads to an additional change in the first.​

A negative (balancing) feedback is one in which the initial perturbation is weakened by the changes it causes.​

A positive (reinforcing) feedback is one in which the initial perturbation is enhanced.​

Question 11

What are fast and slow Climate Feedbacks?​ Give Examples​

Answer 11

Fast feedbacks occur rapidly enough in response to a change in surface temperature that they will play an important role in the evolution of climate change over the coming century. ​

Fast feedbacks include the water vapor feedback, cloud feedback and ice albedo feedback due to melting seas ice or snow. ​

Slow feedbacks include processes that respond slowly to increasing surface temperature, so they require long periods of warmth before they significantly alter energy in or energy out. ​

Slow feedbacks include the carbon cycle feedback (as well as ice albedo feedback due to melting land ice e.g. glaciers or Antarctica).​

In general, slow feedbacks are much more uncertain than fast feedbacks because they are so slow that modern Earth science, which is really only a few decades old, simply does not have data extending over periods long enough to observe, understand, and quantify them. Thus, the net effect of slow feedbacks on the climate is uncertain. ​

Question 12

Explain the Water Vapor Feedback​

Answer 12

the higher the temperature the higher the concentration of water vapor in the atmosphere​

water vapor is a very potent GHG​

more water vapor -> stronger the Greenhouse Effect -> rising temperature -> more water vapor​

positive feedback = additional warming​

Question 13

Explain the Ice Albedo Feedback​

Answer 13

ice sheets have a higher albedo and therefore (usually) cooling effect​

melting ice -> lower albedo -> less reflection -> more warming -> melting ice​

positive feedback = additional warming​

Question 14

Explain the Carbon Cycle Feedback​

Answer 14

Decrease in Carbon Sink Function​
- most additional carbon is sequestered in the ocean and land. This excess of carbon might make these sinks less effective.​
- carbon sinks can eventually turn into carbon sources​

Several pathways for carbon cycle feedbacks: ​

Oceans: rising carbon concentration in oceans -> rising ocean acidity -> dying of ocean fauna -> fewer organisms to absorb oceanic carbon + decrease in efficiency of biological pump -> rising carbon concentration in the oceans + slow down in ocean circulation to deep ocean where carbon can be stored​

Terrestrial: increasing temperatures -> less optimal conditions for organisms -> less photosynthesis -> more carbon -> increasing temperatures​

​–> positive feedback = additional warming ​

Question 15

Table Projected Service Temperature ​

Explain which factors contribute to the uncertainty range in these IPCC’s model projections of future climate changes​

Answer 15

Climate Sensitivity​
- Definition: Temperature increase due to doubling of CO₂.​
Contribution to uncertainty: Different models predict varying temperature increases due to uncertain feedbacks (clouds, water vapor, ice-albedo)​

Future Emission Pathways (SSPs)​
- Definition: Scenarios based on socioeconomic factors, policy, and technology.​
- Contribution to uncertainty: Uncertainty in human activities and policy effectiveness leads to varying emission levels (e.g., SSP1-1.9 vs. SSP5-8.5)​

Feedback Processes​
- Definition: Carbon cycle, cloud feedbacks, vegetation changes.​
- Contribution to uncertainty: Uncertain net effect; can amplify (positive) or dampen (negative) warming, varying among models​

Natural Variability​
- Definition: Includes ENSO, volcanic activity, solar changes.​
- Contribution to uncertainty: Causes short-term temperature fluctuations, affecting near-term projections​

Model Structures and Parameters​
- Definition: Model resolution, process simulation (convection, cloud formation).​
- Contribution to uncertainty: Different structures and parameters lead to varying outcomes for the same scenario​

Socioeconomic & Technological Developments​
- Definition: Policy implementation, renewable energy adoption.​
- Contribution to uncertainty: Uncertainty in achieving net-zero targets affects future emissions and warming​

Question 16

What is the IPCC?​

Answer 16

IPCC = Intergovernmental Panel on Climate Change​

created in 1988 ​

195 member states​

It reviews and assesses, at regular intervals, the most recent scientific information​

goal is provide governments at all levels with scientific information that they can use to develop climate policies​

experts volunteer their time as IPCC authors to assess the thousands of scientific papers published each year to provide a comprehensive summary of what is known about the drivers of climate change, its impacts and future risks, and how adaptation and mitigation can reduce those risks​

Question 17

What is the AR6?​

Answer 17

The Sixth Assessment Report of the IPCC was published in 2023​

It is the most recent report from the IPCC and draws the most drastic conclusions on the state of our climate​

Question 18

What does the AR6 state about the human influence on our climate?​

Answer 18

It is unequivocal that human influence has warmed the atmosphere, ocean and land. Widespread and rapid changes in the atmosphere, ocean, cryo-sphere and biosphere have occurred.​

Question 19

How do we know that humans are responsible for climate change?​

Answer 19

The change in our climate is unprecedented. No natural factors (solar activity or volcanic activity) can explain this degree of change. IPCC uses multiple lines of evidence: ​

no climate model can explain climate change without taking human activity into account​

the rate of warming we have seen over the last decades is more rapid than other (natural) climate warmings seen in the past ​

evidence that CO2 from fossil fuels plays a key role in heightened Greenhouse Effect​

Question 20

What are the three types of Carbon Budgets?​

Answer 20

1.Remaining Carbon Budget:​

describe the total net amount of CO2 that human activities can still release into the atmosphere while keeping global warming to a specified level, like 1.5°C or 2°C relative to pre-industrial temperatures.​

2. Historical Carbon Budget​

a way of describing all past and present sources and sinks of CO2. - It describes how the CO2 emissions from human activities have redistributed across the various CO2 reservoirs of the Earth system -> oceans, atmosphere & land vegetation.​

3. Total Carbon Budget​

Adding these historical CO2 emissions to estimates of remaining carbon budgets allows an estimate of the total carbon budget consistent with a specific global warming level.​

Question 21

What is the Earth’s Energy Budget and how does it relate to Climate Change?​

Answer 21

The Earth’s energy budget describes the flow of energy within the climate system. ​

​Since at least 1970 there has been a persistent imbalance in the energy flows that has led to excess energy being absorbed by the climate system. ​

​By measuring and understanding these energy flows and the role that human activities play in changing them, we are better able to understand the causes of climate change and project future climate change more accurately.​

Question 22

What does the AR6 say about limiting future climate change?​

Answer 22

From a physical science perspective, limiting human-induced global warming to a specific level requires limiting cumulative CO2 emissions, reaching at least net zero CO2 emissions, along with strong reductions in other greenhouse gas emissions. Strong, rapid and sustained reductions in CH4 emissions would also limit the warming effect resulting from declining aerosol pollution and would improve air quality.​

Question 23

How does the AR6 predict possible climate futures?​

Answer 23

The IPCC uses a combination of climate models, scenarios, and observational data to predict possible climate futures. The key method involves the use of Shared Socioeconomic Pathways (SSPs) and climate models to simulate how the climate may respond to different levels of greenhouse gas emissions and socio-economic developments. ​

Question 24

What uncertainties come with the emissions scenarios ?​

Answer 24

Scenario uncertainty: How much CO2 and other GHGs are emitted until 2100?​
- Model uncertainty: How do we model the climate systems response to drivers in change? How do we model effectiveness of CO2 sinks, feedbacks, sensitivity etc. ?​

Scenario uncertainty: to give us an idea of what emission to expect this century the IPCC’s fifth assessment report uses what they called illustrative scenarios. They are estimations about how much CO2 might be emitted or taken out of the atmosphere​
- Model uncertainty: uncertainty in the response of the climate system to a radiative forcing scenario. This is related to:​
- Climate sensitivity​
- Effectiveness of CO2 sinks​
- feedbacks​

Question 25

What aspects of climate change does the AR6 analyze ?​

Answer 25

The AR6 covers projections about:​

Global temperature rise: likely global temperature increases under different SSP scenarios. In the worst-case SSP5-8.5, global temperatures could rise by over 4°C by 2100.​

Sea level rise: Predictions vary depending on emissions levels, but sea levels are expected to continue rising due to thermal expansion and ice melt.​

Extreme weather events: Increased frequency and intensity of heatwaves, droughts, storms, and heavy precipitation are predicted across most regions.​

Ocean changes: Ocean warming, acidification, and reduced oxygen levels are projected to continue, affecting marine ecosystems.​

Regional impacts: Specific projections are made for different regions, considering local variables like topography, ecosystems, and socio-economic conditions.​

Question 26

What is Climate Sensitivity ?​

Answer 26

The change in the surface temperature in response to a change in the atmospheric carbon dioxide (CO2) concentration or other radiative forcing.​

It is measured in °C​

Question 27

What is Equilibrium Climate Sensitivity ?​

Answer 27

CS is defined as the temperature rise associated with a doubling of CO2 above its pre-industrial concentration once the planet has come to equilibrium.​

It is measured in °C​

Doubling of CO2 -> warming -> feedbacks -> ECS​

Question 28

What Data is ECS based on?​

Answer 28

ECS based on multiple lines of evidence​
- observations of historical warming ​
- evidence of past climates (“palaeoclimate” data) ​
- physical understanding of climate processes ​
- does not rely directly on climate models; climate models are not considered a line of evidence in their own right​

Question 29

How does ECS relate to future warmings ?​

Answer 29

there are high uncertainties related to ECS. We do not know how climate feedbacks will play out. ​

Models with high ECS lead to more drastic projections, ergo higher degrees in warming projected by the model.​

The AR6 concludes that there is a 90% or more chance (very likely) that the ECS is between 2°C and 5°C.​

Although these higher warming levels are not expected to occur, high-ECS models are useful for exploring low-likelihood, high-impact futures.​