Climate Science Exam Summary Flashcards
Define resilience
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).
Define vulnerability
The degree to which geophysical, biological and social-economic systems are susceptible to and unable to cope with adverse impacts of climate change (IPCC).
Define maladaptation
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).
Define mitigation
An anthropogenic intervention to reduce the sources or enhance the sinks of greenhouse gases (IPCC).
Define adaptation
Initiatives and measures to reduce the vulnerability of natural and human systems against actual or expected climate change effects (Baede et al, 2007)
Climatic impacts definition
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).
Climatic impacts
Potential impacts definition
All impacts that may occur given a projected change in climate, without considering adaptation (IPCC).
Climatic impacts
Residual impacts definition
The impacts of climate change that would occur after adaptation (IPCC).
The energy balance can be described via net radiation
This is…
the balance between the incoming and outgoing radiation for the planet- measured at the tropopause.
What can cause a temperature change?
A perturbation (such as a change in GHG concentration) can drive a change in net radiation, temporarily disturbing the balance
What is radiative forcing?
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.
What happens in negative radiative forcing?
- Less solar energy in (e.g change in solar constant )
- Overall reduction of energy in system
- Over time, temperature decreases
- Over time, emissions decrease to reach new balance
What happens in positive radiative forcing?
- No change in radiation in but a temporary decrease in radiation out (more absorbing in troposphere)
- Temperature increases over time as a result
over time - Earth’s IR emissions adjust to restore balance
What is a teleconnection?
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
What determines the weather experienced in a place?
Atmospheric circulation and latitude
What is atmospheric circulation driven by?
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.
What do intra-annual climate data show?
What do inter-annual climate data show?
seasonal patterns, short term variability- a seasonal or monthly value can be compared with a longer term mean.
Variation from year to year.
What happens in a normal situation?
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.
What is La Nina?
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).
What is El Nino?
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.
What is ENSO?
El Nino southern oscillation
What are the components of climate?
Atmosphere Earth's Surface Biosphere Ocean Cryosphere
Many other features contribute to radiative forcing ….
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)
Sink vs source
Sink: net going in of carbon
Source: net going out of carbon
Carbon in biota roughly equals carbon in ATM
so..
Change in growth vs destruction of vegetation can alter the carbon balance—variable year-to-year
Carbon in ocean mixed layer roughly equals carbon in ATM
so…
Ocean can absorb extra carbon
– ‘Missing’ anthropogenic CO2 – in ocean?
– Deep ocean reservoir - once in ocean sediments, C is locked
up
Stores of carbon in the terrestrial system
Living biomass (photosynthesis) Soil organics (especially peatlands) Organic compounds in permafrost Fossil fuels (oil, coal, gas)
Human impacts on land-atmosphere carbon flux
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
What direction are natural and anthropogenic fluxes?
Natural fluxes are variable and bi-directional
Anthropogenic fluxes are largely unidirectional
What is the highest of any flux component of the global carbon budget?
The uncertainty on land use change emissions
What can be used to analyse climate changes?
Tree ring data
Thawing northern permafrost
Carbon in the ocean
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)
What is ocean acidification?
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
Why is there limits to weather forecasting?
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.
Start simple…….
Make process models of different components, e.g.
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
Information to construct a model
Radiation fluxes Dynamics of fluids Moisture fluxes and processes Surface processes Surface-atmosphere energy exchanges
An ocean (OGCM) model needs to deal with (for example)
Energy exchange among levels Salt transport Upwelling Horizontal and vertical circulation Sea ice
All models must be provided with…
Starting values. Initial conditions affect subsequent output (“butterfly effect”)
Data assimilation
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
Parameterisation
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
How fast do the components of the climate system respond to forcing?
“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
HOW DOES A MODELLING EXPERIMENT GET DONE?
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)
COMPARING EQUILIBRIUM AND TRANSIENT RUNS Equilibrium runs
– 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
COMPARING EQUILIBRIUM AND TRANSIENT RUNS
Transient runs
- more expensive
- more realistic – and provide time series output - used for 21st century warming projections
SOURCES OF UNCERTAINTY IN MODELLING EXPERIMENTS
- 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) - 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).
- Future scenarios (e.g. GHG emissions values that are input to models) form a wide range of possible futures
Necessary simplifications lead to inaccuracies
Simulated annual global mean surface temperatures
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
What is the aerosol thats most likely a positive forcing?
Black carbon/ soot landing on ice sheet and changing albedo
What is attribution?
Attribution of recent climate change is the effort to scientifically ascertain mechanisms responsible for recent climate changes on Earth
Main points of attribution?
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.
Example of water vapour (positive feedback)?
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.
Example of albedo (positive feedback)?
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.
Land carbon cycle (currently negative feedback)
Global warming could affect the process in two ways:
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.
Exemplify some alternative forces in the worlds oceans that are becoming barriers to adaptation?
- 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.
What is an ecotone?
What is an ecotonal boundary?
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
