Introduction to greenhouse gases

Question 1

What does the IPCC stand for?

Answer 1

Intergovernmental Panel on Climate Change

Question 2

What is the purpose of the IPCC?

Answer 2

An intergovernmental body of the United Nations providing the world with objective, scientific information relevant to understanding the scientific basis of the risk of human-induced climate change, its natural, political, and economic impacts and risks, and possible response options.
These are released as reports (AR1, AR2 … AR6).

Question 3

What are the triple crises recognised by the IPCC?

Answer 3

• Biodiversity loss
• Pollution
• Climate change

Question 4

What does the UNFCCC stand for?

Answer 4

The United Nations Framework Convention on Climate Change

Question 5

What is the purpose of the UNFCCC?

Answer 5

“Seeks for the stabilization of greenhouse gas concentrations in the atmosphere at a level that would prevent dangerous anthropogenic human-induced interference with the earth’s climate system”

Question 6

What does COP stand for and which organisation runs them?

Answer 6

The UNFCCC holds an annual Conference of the Parties.

Question 7

What did COP29 achieve?

Answer 7

• Triple finance to developing countries (now USD 300 billion annually by 2035) via both public and private sectors

Question 8

Describe Huronian snowball Earth.

Answer 8

• 2.5 - 2.1 Gya
• Oceans froze (slightly slushy at the equator)
• Massive extinction

Question 9

How long might the next glaciation be delayed by as a result of global warming from fossil fuel combustion?

Answer 9

500,000 years

Question 10

What are Dansgaard-Oeschger cycles?

Answer 10

Rapid climate change (rapid warming then gradual cooling) during the last glaciation.

Question 11

What was the sudden warming then gradual cooling observed in Greenland ice cores in the last glaciation referred to as?

Answer 11

Dansgaard-Oeschger cycles

Question 12

What caused Dansgaard-Oeschger cycles?

Answer 12

Fluctuations in the Atlantic Meridional Overturning Circulation (AMOC), a major ocean current system that transports heat from the tropics towards the North Atlantic.

Question 13

What do Dansgaard-Oeschger cycles suggest for the future?

Answer 13

D–O cycles show that past fluctuations in the AMOC caused rapid climate shifts, especially in the North Atlantic region. This suggests that if global warming weakens the AMOC (as expected), it could lead to sudden and drastic regional climate changes in the future — not just gradual warming.

Question 14

Is the Atlantic Meridional Overturning Circulation (AMOC) predicted to change in future?

Answer 14

It is expected to weaken with rising temperatures due to increased freshwater influx from melting ice and changes in ocean salinity. This will make the water less dense, therefore less likely to sink, slowing the circulation.

Question 15

Is the greenhouse effect “good”?

Answer 15

It is critical to our survival - without it the planet would be uninhabitable.

Question 16

Describe the greenhouse effect.

Answer 16

1. Sunlight passes through the atmosphere and warms the surface of the Earth
2. Infrared radiation is given off by the Earth
3. Most IR escapes back to outer space, cooling the Earth
4. Some IR is trapped by gases in the atmosphere, reducing the cooling

Question 17

What do CFCs stand for? Where in the atmosphere are they found and how have their concentrations changed?

Answer 17

Chlorofluorocarbons.
They are found in the troposphere and have increased dramatically in concentration.

Question 18

What are three significant greenhouse gases other than CFCs?

Answer 18

• CO2
• N2O
• Methane

Question 19

Why are there oscillations in the concentration of carbon dioxide in the atmosphere over time?

Answer 19

Seasonal variations in natural sources and sinks:
- Seasonal growth in spring and summer in the northern hemisphere reduces CO2 atmospheric concentrations due to increased photosynthetic uptake
- The decay of plants in the northern hemisphere in autumn and winter causes an increase in CO2 concentrations again

Question 20

What are some of the causes of seasonal fluctuations in atmospheric methane?

Answer 20

Mainly microbial activity in wetlands and the seasonal variation of OH radicals.
Wetlands emit more methane in summer due to warm, wet conditions.
Methane is removed more quickly in the summer/early autumn because of high OH levels
Therefore: winter highs and summer lows in CH₄ concentrations.

Question 21

What two factors drive the global warming potential of a greenhouse gas?

Answer 21

• The compound’s infrared absorption spectrum at wavelengths not absorbed by water and CO2
• Residence times

Question 22

Which type of gas exhibits the greatest contribution to the greenhouse effect?

Answer 22

CFC-12

Question 23

What is radiative forcing?

Answer 23

Incoming energy - outcoming energy

Question 24

Which year is RF expressed relative to? How is RF changing?

Answer 24

1750
It is increasing (greater proportion is incoming but not outgoing).

Question 25

What are the three major soil-borne greenhouse gases?

Answer 25

- CO2 - CH4 - N2O

Question 26

How much greater are the potentials of CH4 and N2O as greenhouse gases than that of CO2?

Answer 26

CH4 = 34 times N2O = 264 times

Question 27

What are the rough ppms for CO2, CH4 and N2O?

Answer 27

CO2 = 420 ppm CH4 = 1.9 ppm N2O = 0.32 ppm or 320 ppb

Question 28

Describe the positive feedback effects related to the evaporation of water.

Answer 28

- If the atmosphere is warmed, the saturation vapour pressure increases (air can hold more water vapor without condensation), and the quantity of water vapor in the atmosphere will tend to increase. - Water vapour is a greenhouse gas, therefore causing more atmospheric warming - This means more water vapour can be held by the atmosphere....

Question 29

Does the feedback loop driven by water evaporation produce a greater greenhouse effect than CO2 alone?

Answer 29

Yes

Question 30

What is the runaway greenhouse effect?

Answer 30

A positive feedback cycle where increasing temperatures cause increasing accumulation of greenhouse gases in the atmosphere, causing more warming...

Question 31

What are the implications of the runaway greenhouse effect? Where was this observed?

Answer 31

- Water-rich atmosphere reaches 1400K - Oceans evaporate - Life is extinguished Observed on Venus

Question 32

What is GWP and what does it stand for?

Answer 32

Global Warming Potential (GWP) = comparison of how much heat is trapped relative to CO2

Question 33

What is GTP and what does it stand for?

Answer 33

Global Temperature change Potential (GTP) = how much surface temperature change relative to CO2

Question 34

How can greenhouse gases be compared?

Answer 34

Using Global Warming Potential (GWP) and Global Temperature change Potential (GTP)

Question 35

Why is methane’s GWP₂₀ higher than its GWP₁₀₀?

Answer 35

Methane is a potent greenhouse gas with a short atmospheric lifetime (~12.4 years). Over 20 years, most of its warming potential is still active, giving it a high GWP₂₀ (84–86). By 100 years, much of it has broken down, so its GWP₁₀₀ drops to 28–34.

Question 36

Why is it important to compare GWP₂₀ to GWP₁₀₀?

Answer 36

It shows the long term effects -> this can be used to inform climate plans. For example: Reducing methane quickly can significantly lower near-term warming, which is why global initiatives like the Methane Pledge (COP26) target short-term methane cuts (as it has a short term atmospheric life).

Question 37

What is the main goal of the Paris Agreement?

Answer 37

To limit global warming to well below 2°C above pre-industrial levels, and pursue efforts to limit it to 1.5°C, in order to avoid the most severe impacts of climate change

Question 38

How many countries have ratified the Paris Agreement?

Answer 38

190 out of 197 parties to the United Nations Framework Convention on Climate Change (UNFCCC) have ratified the agreement.

Question 39

What are “Intended Nationally Determined Contributions” (INDCs)?

Answer 39

INDCs are climate action plans submitted by each country that outline how they plan to reduce greenhouse gas emissions. These form the core of each country’s mitigation commitments under the Paris Agreement.

Question 40

What is climate geoengineering?

Answer 40

Large-scale, deliberate interventions in the Earth's climate system to counter the effects of anthropogenic climate change. It is considered when GHG levels cannot be sufficiently reduced.

Question 41

What are example methods of climate geoengineering?

Answer 41

- Space satellites (reflect incoming solar radiation) - Aerosol injection in the stratosphere - Brightening marine clouds - Making the ocean surface more reflective - Growing more reflective plants - Whitening roofs and other built structures

Question 42

Why is climate geoengineering controversial?

Answer 42

- It only addresses the effects - not the cause - Inherent risks of unintended consequences - Efficacy difficult to determine - Unclear regulation of deployment

Question 43

What does NETs stand for? What do they aim to do and how is this achieved?

Answer 43

Negative Emission Technologies Aim to remove greenhouse gases (primarily CO2) from the atmosphere using either photosynthetic or chemistry techniques

Question 44

What are some examples of NETs?

Answer 44

- Afforestation or Reforestation (AR) - Biochar - Soil carbon sequestration

Question 45

What needs to be checked before NETs implementation?

Answer 45

- Are the tools ready for implementation - Assess the costs vs the potential (long term benefits and negatives)