Climate Science Exam Summary

Question 1

Define resilience

Answer 1

The ability of a social or ecological system to absorb disturbances while retaining the same basic structure and ways of functioning, the capacity of self organisation and the capacity to adapt to stress and change (IPCC).

Question 2

Define vulnerability

Answer 2

The degree to which geophysical, biological and social-economic systems are susceptible to and unable to cope with adverse impacts of climate change (IPCC).

Question 3

Define maladaptation

Answer 3

Any changes in natural or human systems that inadvertently increase vulnerability to climate stimuli; an adaptation that does not succeed in reducing vulnerability but increase it instead (IPCC).

Question 4

Define mitigation

Answer 4

An anthropogenic intervention to reduce the sources or enhance the sinks of greenhouse gases (IPCC).

Question 5

Define adaptation

Answer 5

Initiatives and measures to reduce the vulnerability of natural and human systems against actual or expected climate change effects (Baede et al, 2007)

Question 6

Climatic impacts definition

Answer 6

Consequences of climatic change on natural and human systems. Depending on the consideration of adaptation, one can distinguish between potential impacts and residual impacts (IPCC).

Question 7

Climatic impacts

Potential impacts definition

Answer 7

All impacts that may occur given a projected change in climate, without considering adaptation (IPCC).

Question 8

Climatic impacts

Residual impacts definition

Answer 8

The impacts of climate change that would occur after adaptation (IPCC).

Question 9

The energy balance can be described via net radiation

This is…

Answer 9

the balance between the incoming and outgoing radiation for the planet- measured at the tropopause.

Question 10

What can cause a temperature change?

Answer 10

A perturbation (such as a change in GHG concentration) can drive a change in net radiation, temporarily disturbing the balance

Question 11

What is radiative forcing?

Answer 11

A change in net radiation driving a temperature change- not necessarily a change in radiation—e.g., incoming solar—but a change that affects net radiation.

Question 12

What happens in negative radiative forcing?

Answer 12

1. Less solar energy in (e.g change in solar constant )
2. Overall reduction of energy in system
3. Over time, temperature decreases
4. Over time, emissions decrease to reach new balance

Question 13

What happens in positive radiative forcing?

Answer 13

1. No change in radiation in but a temporary decrease in radiation out (more absorbing in troposphere)
2. Temperature increases over time as a result
   over time
3. Earth’s IR emissions adjust to restore balance

Question 14

What is a teleconnection?

Answer 14

Dynamics of atmosphere mean circulation conditions in one region may be linked to those in another.

e.g Existence of high pressure over Russia led to a deflection of jet streams that acted as a trigger for an abnormal start to the Asian monsoon (came before it should)- lots of heavy rain in a short period of time

Question 15

What determines the weather experienced in a place?

Answer 15

Atmospheric circulation and latitude

Question 16

What is atmospheric circulation driven by?

Answer 16

Energy exchanges, primarily the equator pole heat differential.

Changing the energy balance introducing more heating capacity into the lower atmosphere in the surface, energy comes in at the equator into these circulation systems and ends up being transported to polar regions which loses energy, distributing energy around the planet.

Question 17

What do intra-annual climate data show?

What do inter-annual climate data show?

Answer 17

seasonal patterns, short term variability- a seasonal or monthly value can be compared with a longer term mean.

Variation from year to year.

Question 18

What happens in a normal situation?

Answer 18

In the pacific, trade winds blow from east to west.
They blow warm water, which piles up on the western side of the ocean (asia).
On the eastern side, cold water upwelling replaces the warm water.
A temperature difference is thus created.
The warm water zone causes rising air- more cloud and rainfall.
This sets up atmospheric circulation- cool, dry air descends in the east.

Question 19

What is La Nina?

Answer 19

A turbo charged normal situation.
Normally the warm water pulls up in the western pacific, much more upwelling and colder conditions in the eastern pacific (drought).

Question 20

What is El Nino?

Answer 20

Trade winds weaken- warm surface water moves eastwards.
Reducing upwelling near South America.
Warmer ocean causes an intensification and southward shift of the jet stream = flooding, and warmer dryer conditions.

Question 21

What is ENSO?

Answer 21

El Nino southern oscillation

Question 22

What are the components of climate?

Answer 22

Atmosphere
Earth's Surface
Biosphere
Ocean 
Cryosphere

Question 23

Many other features contribute to radiative forcing ….

Answer 23

Mt Pinatubo (Philippines) 1992 ash and aerosols caused global climate cooling (-ve forcing) over several years
Con trains also a radiative forcing component
Smog produced by industry or by agricultural fires (burn off fields for nutrients)
Bright ash clouds and smog -> negative forcing via reflection of incoming radiation
Sooty smog -> positive forcing (absorbs radiation and warms)

Question 24

Sink vs source

Answer 24

Sink: net going in of carbon
Source: net going out of carbon

Question 25

Carbon in biota roughly equals carbon in ATM

so..

Answer 25

Change in growth vs destruction of vegetation can alter the carbon balance—variable year-to-year

Question 26

Carbon in ocean mixed layer roughly equals carbon in ATM

so…

Answer 26

Ocean can absorb extra carbon
– ‘Missing’ anthropogenic CO2 – in ocean?
– Deep ocean reservoir - once in ocean sediments, C is locked
up

Question 27

Stores of carbon in the terrestrial system

Answer 27

Living biomass (photosynthesis)
Soil organics (especially peatlands)
Organic compounds in permafrost
Fossil fuels (oil, coal, gas)

Question 28

Human impacts on land-atmosphere carbon flux

Answer 28

Burning of fossil fuels (industrialisation)
Forest clearance and land cover change
Episodic release of CO2 via burning for clearance and icnreased decay rates
Agricultural practices e.g. ploughing, wet rice cultivation
Reforestation/ afforestation (temporary increase co2)
Uptake by regrowth/ young plantations

Question 29

What direction are natural and anthropogenic fluxes?

Answer 29

Natural fluxes are variable and bi-directional

Anthropogenic fluxes are largely unidirectional

Question 30

What is the highest of any flux component of the global carbon budget?

Answer 30

The uncertainty on land use change emissions

Question 31

What can be used to analyse climate changes?

Answer 31

Tree ring data

Thawing northern permafrost

Question 32

Carbon in the ocean

Answer 32

Ocean mixed layer dissolved inorganic carbon (DIC) <1% is dissolved CO2

Most DIC is in a buffering system
Carbon dioxide dissolves to form carbonic acid, which dissociates into ions of 2 valencies (plus protons, H+) and hold a lot of Co2 that’s not Co2 (has several different ionic identities in water)

Question 33

What is ocean acidification?

Answer 33

Production of more biocarbonate buffer soaks up some of the H+ but not all, and the consequence is that there is less CO3 2- .
This critical for shell-making fauna and corals that use CO3 2 – ocean acidity is reaching levels that may affect physiological function

Question 34

Why is there limits to weather forecasting?

Answer 34

The dynamics of atmosphere and ocean are partially chaotic.
Initial conditions are critical – the further from the present moment the simulation evolves, the greater the error of the forecast.
Climate models are less subject to the initial conditions problem. They generate [daily] weather over many years (not just a few days) and their output can be summarised as climate statistics.

Question 35

Start simple…….

Make process models of different components, e.g.

Answer 35

Make process models of different components, e.g.
Energy exchange- radiation
Land-surface

First test: Can the model reproduce observations? If so, what does it simulate with a perturbation? * it’s mean ought to be approximately the same as that of the real world

Then the model can be used to see what happens when you change things
*Changing something in the system

Question 36

Information to construct a model

Answer 36

Radiation fluxes
Dynamics of fluids
Moisture fluxes and processes
Surface processes
Surface-atmosphere energy exchanges

Question 37

An ocean (OGCM) model needs to deal with (for example)

Answer 37

Energy exchange among levels 
Salt transport 
Upwelling 
Horizontal and vertical circulation 
Sea ice

Question 38

All models must be provided with…

Answer 38

Starting values. Initial conditions affect subsequent output (“butterfly effect”)

Question 39

Data assimilation

Answer 39

Used particularly in weather forecasting but also in palaeoclimate modelling.
Start model, run forward, assess model output and compare with observed data. Repeat.
Can do this for daily weather, hurricane prediction, or use palaeodata on long time scales

Question 40

Parameterisation

Answer 40

Some processes happen at scales far smaller than the grid size processes represented with simplified (and thus probably inaccurate) equations example: many cloud-formation processes
Parameterizations can be evaluated using perturbed physics ensembles

Question 41

How fast do the components of the climate system respond to forcing?

Answer 41

“Fast” feedbacks and equilibration
Water vapour, clouds – ‘instantaneous’ (hours, days)
Snow, sea-ice – seasonally
Vegetation/carbon changes – minutes/hours, seasonally

“Slower” feedbacks and equilibration
Vegetation (drought, treeline shifts) – decades/centuries
Ocean carbon cycle, conveyor belt, other terrestrial changes (e.g. glaciers) – centuries

Question 42

HOW DOES A MODELLING EXPERIMENT GET DONE?

Answer 42

It is a controlled experiment
Baseline run (control: usually present day) – no perturbations
Experimental run – perturbation
Compare control and experiment

DEALING WITH TIME
Change is either executed instantaneously (2 equilibria: before and after)
OR change is executed gradually over many time steps (transient)

Question 43

COMPARING EQUILIBRIUM AND TRANSIENT RUNS Equilibrium runs

Answer 43

– cheaper

• exploratory
• often overestimate change in temperature compared with a transient run with the same overall forcing
• used for palaeoclimate experiments, eg the Eocene, Snowball Earth

Question 44

COMPARING EQUILIBRIUM AND TRANSIENT RUNS

Transient runs

Answer 44

• more expensive

- more realistic – and provide time series output - used for 21st century warming projections

Question 45

SOURCES OF UNCERTAINTY IN MODELLING EXPERIMENTS

Answer 45

1. Perturbation a complex set of responses
   The particular construction of a model (e.g. the specific parameterizations it uses) may make it more or less sensitive to a perturbation
   (Hence model ensembles – as in the IPCC)
2. Some feedbacks take time to kick in and may increase the initial forcing – but how much? Some of these are not yet incorporated in models (e.g. permafrost thaw).
3. Future scenarios (e.g. GHG emissions values that are input to models) form a wide range of possible futures

Necessary simplifications lead to inaccuracies

Question 46

Simulated annual global mean surface temperatures

Answer 46

Natural
- Sun and volcanoes
- Omits anthropogenic
Anthropogenic
- Human 
- Omits natural
All forcings
- Red doesn't change in all observations
- Key experiment : anthropogenic forcing becomes evident in past 30 yr
- Not possible to replicate observations unless anthropogenic GHGs added

Question 47

What is the aerosol thats most likely a positive forcing?

Answer 47

Black carbon/ soot landing on ice sheet and changing albedo

Question 48

What is attribution?

Answer 48

Attribution of recent climate change is the effort to scientifically ascertain mechanisms responsible for recent climate changes on Earth

Question 49

Main points of attribution?

Answer 49

Total radiative forcing is positive- energy uptake by climate system.
Largest contribution is increase of CO2 since 1750.
Human influence detected in warming of atmosphere, ocean. Plus snow/ ice reduction and sea level rise.
Warming has become clear since about 1980- extremely likely human influence is dominant cause.

Question 50

Example of water vapour (positive feedback)?

Answer 50

As air gets warmer, its capacity to hold moisture increases. Our atmosphere is getting warmer because of climate change and, as a result, is holding more water vapour. This is a potent greenhouse gas - when in the atmosphere, water vapour helps the Earth hold on to more energy from the sun. So a warming climate means more water vapour, which in turn warms the climate further - a classic positive feedback.

Question 51

Example of albedo (positive feedback)?

Answer 51

Global warming is causing ice and snow to melt, revealing the land or ocean underneath. Ice and snow reflect a lot of sunlight - certainly more than land and the oceans. So as the ice melts, more of the sun’s energy is absorbed and so the planet gets warmer still - which in turn melts even more snow and ice.

Question 52

Land carbon cycle (currently negative feedback)

Global warming could affect the process in two ways:

Answer 52

Oceans

As the ocean absorbs CO2 it becomes more acidic, reducing the amount of CO2 it can further absorb.
As the temperature of the ocean increases this reduces its capacity to absorb CO2.

Land - climate change can affect the land in a variety of ways, including:

Negative climate feedback as temperatures increase because the areas in which trees can grow will extend north to higher latitudes. New trees will absorb CO2, taking it out of the atmosphere.
Positive feedbacks around the tropical zones. As temperatures increase, soils, plants and trees in these areas will become more heat stressed - potentially releasing the huge amounts of carbon they store and even threatening the future of important areas such as the Amazon rainforest.

Question 53

Exemplify some alternative forces in the worlds oceans that are becoming barriers to adaptation?

Answer 53

• Input of nutrients such as nitrogen and phosphorus in coastal waters
• Mining
• Offshore windfarms
• Losing coral cover/mangrove areas for a host of reasons
• Heavy ship traffic

…all affect how species adjust to changing conditions.

Question 54

What is an ecotone?

What is an ecotonal boundary?

Answer 54

An ecotone is where one biome meets another.
Different biomes have different velocities (can move away from each other).

Ecotonal boundary opens - what happens in between = novice ecosystems