climate change - 1

Question 1

What is Climate change?

Answer 1

• Climate change refers to a statistically significant variation in either the mean state of the climate or in its variability, persisting for an extended period - typically decades or longer.
• Climate change may be due to natural internal processes or external forcing, or to persistent anthropogenic changes in the composition of the atmosphere or in land-use.
• Global climate change is a serious and urgent issue.

Question 2

Global warming and climate change

Answer 2

• Global warming causes climate change
• Global warming is a problem in which the combustion of coal, oil and other fossil fuels causes the atmospheric concentrations of GHGs such as carbon dioxide, to increase.
• This results in mounting global air temperatures that lead to climate change

Question 3

The basic science behind global warming - The Greenhouse effect

Answer 3

• Global warming is caused by greenhouse gases (GHG), a type of global pollutants
• The three most anthropogenic greenhouse gases are CO2, methane(CH4 ) and nitrous oxide (N2O), the levels of which have risen since the Industrial revolution.
• The sun sends energy in every direction some of which reaches the planet earth
• These global pollutants absorb the long-wavelength (infrared)radiation from the earth’s surface and atmosphere, trapping heatthat would otherwise radiate into space. Hence it is harder for energy to leave the planet than if there were no GHGs.
• This warms earth surface 30°C above normal

Question 4

Global warming over the years

Answer 4

• The world is now more than 1.10 C warmer than it was in late 19th century.
• Human activities - mostly post-industrial revolution, have changed the composition and level ofGHG in atmosphere.
• CO2 : 280 ppm (pre industrial) to (approx.) 430 ppm today! I.e. it has risen by 50% since the startof Industrial Revolution and it is increasing by 2 ppm each year! (ppm: parts par million – a measure that describes small concentration of substance in a large solution)
• Highest concentrations of GHG for 650,000 years!
• Even if concentrations remained constant from now on, the global temperature would still rise by 1-30 C above pre-industrial levels

Question 5

Global warming stats

Answer 5

• Atmospheric accumulations of GHG stays there for a long time
• The rate of warming currently at 0.130C per decade is increasing.
• IPCC (Intergovernmental panel on climate change) projects a temperature change of 1.50C to4.80 C by 2100!
• The global increases in CO2 concentration are due primarily to fossil-fuel use (e.g. in transport, energy, industries) and land-use (deforestation) changes; whereas methane and nitrous oxide concentrations arise primarily from agriculture
• Emissions are increasing at an increasing rate!

Question 6

Observed impacts and changes - Ocean warming and acidification

Answer 6

• Ocean warming dominates the increase in energy stored in the climate system, accounting for more than 90% of the energy accumulated between 1971 and 2020.
• Since the beginning of the industrial era, oceanic uptake of CO2 has resulted in acidification of the ocean; the pH of ocean surface water has decreased by 0.1corresponding to a 26% increase in acidity.

Question 7

Observed impacts changes - surface temperature

Answer 7

• Each of the last three decades has been successively warmer at the Earth’s surface than any preceding decade since1850.
• The globally averaged combined land and ocean surface temperature data show a warming of 0.85 [0.65 to 1.06] °C over the period 1880 to 2012.

Question 8

Observed impacts and changes - Sea level rise, declining Arctic sea, shrinking ice sheets

Answer 8

• Over the period 1901–2010, global mean sea level rose by 0.19 [0.17 to 0.21] m
• The annual mean Arctic sea-ice extent decreased over the period 1979 to 2012, with a rate that was very likely in the range 3.5 to 4.1% per decade.
• Greenland and Antarctic ice sheets have been loosing mass, glaciers continue to shrink.

Question 9

Projections and future impacts of climate change

Answer 9

• Consequently, people’s lives are changing where the poorest and most vulnerable countries are affected worst despite they usually being the lowest emitters.
• E.g. East Africa has suffered their worst draughts over 40 years, putting more than 20 million people at severe hunger; in 2022 and 2023 European heat waves led to abnormal increase deaths

Question 10

How will future climate change affect our world?

Answer 10

Limiting long-term temperature rises to 1.50 C is absolutely crucial because the consequences of20 C vs 1.50 C could imply more frequent occurrences of extreme events including the following:
 Sea-level rise would be 0.1m higher than at 1.5C, exposing up to 10 million more people to events including more frequent flooding
 Loss of land and forest areas including coral reefs and wetlands => loss of species, extinction of flora and wildlife, marine lives: More than 99% of coral reefs would be lost, compared with70-90% at 1.5C; Loss of agricultural outputs due to draughts.
 Impacts on people: Disruption of water supplies to cities and agriculture; Health damageand deaths due to spread of vector-borne diseases such as malaria, flooding and extremeheat. Several hundred million more people will be exposed to climate-related risks and susceptible to poverty by 2050 than at 1.5C.
 Threshold effects known as Tipping points will create irreversible changes such as complete destruction of ecosystems in the long run if crossed.
 Long term impact on growth and development especially in the poorer countries

Question 11

Net Zero

Answer 11

reducing greenhouse gas emissions as much as possible, and removing any remaining emissions from the atmosphere i.e. all emissions released by human activities are counterbalanced by removing carbon from the atmosphere in a process known as carbon removal

Question 12

Paris agreement

Answer 12

• In a landmark agreement signed inParis in 2015, almost 200 countries pledged to try to keep global warming to 1.5C.
• To achieve this, “net zero“ CO2emissions need to be reached by2050.
• Unfortunately we are nowhere near achieving this.
• In the most recent UN climate change summit, COP28 held in theUAE, countries for the first time, agreed to contribute to”transitioning away from fossil fuels”, although they are not forced to take action!!

Question 13

Pollution targets

Answer 13

o maximising social welfare
o economic efficiency
o sustainability
o minimisation of health risk

Question 14

Pollution flows, pollution stocks and pollution damage

Answer 14

o Pollution can be classified in terms of a damage mechanism.
o Damage can arise from the flow of pollution i.e. the rate of emission; or from the stock (or the concentration rate) of pollution in relevant environmental medium.

Question 15

Flow-damage pollution

Answer 15

Flow-damage pollution occurs when damage results only from the flow of residuals i.e. the rate at which they are being discharged into the environmental system.For pure cases of flow-damage pollution, the damage will drop to zero if emissions flows become zero: e.g. noise or light pollution.

D = D(M)

Question 16

Stock-damage pollution

Answer 16

Stock-damage pollution occurs when damages depend only upon the stock ofthe pollutant in the environment. For a stock of pollutant to accumulate, it is necessary that the residuals have a positive life-span and that emissions are being created at a rate that exceeds the assimilative capacity of the environment.

D = D(A)

Question 17

The efficient level of pollution

Answer 17

Note pollution level cannot be zero! Not economically efficient except for special circumstances. Production will generate some level of pollution in most cases.Hence goods can only be producible in non-pollution ways incurring large costs.

Question 18

Benefits from pollution

Answer 18

If a producing (i.e. a polluting) agent has to reduceits emission level e.g. below the unconstrained level of emission, it incurscosts - costs associated with emission reduction. Hence benefits of pollution = savings associated with emission increases. Hence another interpretation of pollution benefit function is the emission abatement cost function.

Net benefits function: NB(M) = B(M) - D(M)
Problem is to maximise NB(M), B’(M) = D’(M)

Question 19

efficient level of pollution minimises…

Answer 19

Graph on slides
the sum of total abatement costs plus total damage costs

Question 20

Stock pollutants

Answer 20

Damages depend upon the stock level of pollutant.

The majority of important pollution problems are associated with stock pollutants.

Pollution stocks derive from the accumulation of emissions that have a finite life (or residence life) e.g. GHGs - they have a very long residence life.

Analysis of stock pollution requires taking account of space and time

Question 21

Uniform mixing

Answer 21

measured concentration rate of the pollution does not vary from place to place

Question 22

Non-uniform mixing

Answer 22

measured concentration rate of the pollution varies from place to place

Question 23

Where should emission targets for each firm be set?

Answer 23

the private marginal benefit of its emission is equal to the total marginal damage of its emission borne by all receptors

Comment 1. Firms located at different sources have different pollution impacts: those sources with highest pollution impact should emit the least.

Comment 2. With uniform mixing, the above model reduces to the simple flow pollution model. For example, A = kM where k is fixed.

In practice, sometimes environmental regulators may deem that it is uneth-ical to have variations for A from place to place. So sometimes they might place constraints on the acceptable level of A to reflect this unethical position.