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The Science of Climate Change > fundamentals of climate > Flashcards

fundamentals of climate Flashcards

lectures

1
Q

what are the components of the climate system?

A

atmosphere

ocean - including its biosphere

land - including its biosphere

cryosphere - glaciers, ice caps, sea-ice, seasonal snow cover

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2
Q

koppen climate classification determines variation of climate with location and is broadly determined by….

A

latitude, altitude, disatnce from the ocean, seasonal variation of temp and rainfall

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3
Q

temperature falls strongly with height in the…

A

troposphere and increases again in the statosphere

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4
Q

what temperature emits radiative energy?

A

absolute 0 (0 K or -273 degrees celsius) which includes ME!

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5
Q

what is the perfect emitter of radiation called?

A

a black body

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6
Q

what is total energy of the sun emitted per second per metere-squared?

A

T~5800 K

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7
Q

how much energy do we emit? (T - K measurement units )

A

T~300 K

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8
Q

What are good emitters and absorbers of thermal infrared radiation?

A

clouds and many gases in the atmosphere such as CO2 OR H2O

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9
Q

what amount of energy is available to warm the earth and power the earths system?

A

340 W m-2

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10
Q

what amount of sun is reaching the earth? (totar solar irradiance - w m-2)

A

The amount reaching the Earth is called the “Total Solar Irradiance” So ≈ 1360 W m-2

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11
Q

is all of the suns energy absorbed by the earth and if no where does it go?

A

Not all this energy is absorbed by the Earth. Satellite observations show that 30% of it is reflected back to space by clouds (≈15%), the Earth’s surface (≈10%) and atmospheric gases (≈5%)

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12
Q

what is the 30 percent of energy which is not absorbed by the earth and is reflected back to space by clouds, the earths surface and atmospheric gases known as?

A

planetary albedo - normally given as a decimal fraction, 0.3

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13
Q

what amount of energy is absorbed by planet earth? (W m-2)

A

240 W m-2

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14
Q

where is the earths emission and why?

A

in the thermal infrared - because its relatively cold

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15
Q

what percent of what is emitted by the surface reaches space?

A

60 percent
This is because greenhouse gases and clouds absorb the infrared radiation emitted by the surface; because the atmosphere is cooler than the surface, the amount it emits is less than the amount it absorbs
And some of the atmospheric emission is down to the surface, which helps keep the surface warm

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16
Q

how much of the suns energy reaches the surface?(fraction ish number)

A

around two-thirds
– the role of the greenhouse gases is to essentially “trap” that energy in the system, keeping the surface warmer than it otherwise would be

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17
Q

atmosphere is made up of 99 percent of..

A

nitrogen and oxygen
These are simple molecules that are ineffective at absorbing thermal infrared radiation

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18
Q

which main greenhouse gases are responsible for the natural greenhouse effect?

A

h20 - 60 percnt

co2 25 percent
other gases…..ozone, methane nitrous oxide

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19
Q

what percent do clouds contribute of trapping thermal infrared radiation?

A

around 20percent

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20
Q

which parameters determine the earths energy balance?(3 things)

A

the total solar irradiance , the planetary albedo and the concentrations of greenhouse gases, such as CO2

If any of these change they lead to an imbalance in the Earth’s energy budget (called “radiative forcing” – see next week) and the climate system responds (“climate change”) to try to re-establish balance

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21
Q

what is an imbalance in the earths energy budget called

A

radiative forcing

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22
Q

signs of radiative forcing determine whether the climate system….

A

warms or cools

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23
Q

changes in components of the climate system which influence the earths energy budget are called..

A

feedbacks

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24
Q

what do feedbacks do?

A

they can either amplify or reduce the size of climate change

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25
Q

feedbacks + radiative forcing - determine …

A

how large climate change is

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26
Q

water vapour (powerful greenhouse gas) is expected to increase by…

A

7 percent for every degree warming - A POSITIVE FEEDBACK

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27
Q

snow and ice in a warming world are expected to ….

A

decrease the planetary albedo - a POSITIVE FEEDBACK

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28
Q

what is one of the biggest uncertainties in climate change?

A

how clouds respond to climate change? - probably a positive feedback

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29
Q

positive feedback…

A

either speeds up or slows down a warming trend

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30
Q

different types of observations include..

A

direct - temp

remotely sensed- satellites

proxy and paleo - ice cores, tree rings

re analyses sophisticated combo of observations and weather forecast models

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31
Q

issues in measuring climate variables such as precipitation and temperature include…

A

consistency

continuity of measurement method

spatial variability - how many observations are needed to build a reliable pic

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32
Q

observation systems were often designed for providing data for weather forecasting…… this matters because?

A

there are various potential pitfalls in using data for climate trends…. SCEPTICISM when you see this!

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33
Q

sea surface temperature measurement methods used include…

A

buckets

measuring temp of water used to cool ship engines

recently - satellite observations

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34
Q

issues with satellites….

A

short lifespan

passing over the same spot different times of the day - makes it difficult to compare data

joining records together with sellotape

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35
Q

IPCC LANGUAGE….

A

“Virtually certain” = greater than 99% chance that the result is true
· “Very likely” = 90 – 99% chance
· “Likely” = 66 – 90% chance
· “Medium likelihood” = 33-66% chance
· “Unlikely” = 10-33% chance
· “Very unlikely” = 1-10% chance
· “Exceptionally unlikely” = less than 1% chance

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36
Q

how do scientists study ice cores?

A

Scientists can learn about Earth’s climate from the past by studying Antarctic ice cores, which are cylinders of ice drilled from deep within the ice sheets. These ice cores contain tiny air bubbles trapped within the ice, which provide a record of past atmospheric conditions.

One way scientists use ice cores is by measuring the concentration of carbon dioxide (CO2) trapped in these bubbles. By analyzing the air bubbles, scientists can estimate the levels of CO2 in the atmosphere going back nearly 1 million years. This helps us understand how CO2 levels have changed over time.

Another method involves studying the isotopic composition of water molecules in the ice cores. Different isotopes of water have slightly different weights, and the ratio of these isotopes can give scientists clues about past temperatures. By analyzing these isotopes, scientists can infer temperature variations over long periods.

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37
Q

how much has the earth warmed since the “pre-industrial” era?

A

1.2 degrees celsius

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38
Q

is land warming faster than the oceans?

A

yes

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39
Q

is the arctic warming faster than the rest of the globe?

A

yes

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40
Q

is the stratosphere cooling?

A

yes

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41
Q

why is the stratosphere cooling?

A

due to

ozone depletion
and
co2 increases

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42
Q

have hot extremes become more frequent and intense since 1950s?

A

yes

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43
Q

have cold extremes become less frequent and severe?

A

yes

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44
Q

is arctic sea ice at its lowest trend in the past 1000 years?

A

yes

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45
Q

how much is global sea level rise since the 1900

A

0.2 metres

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46
Q

what does ENSO stand for?

A

El Niño-Southern Oscillation,

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47
Q

During its positive phase, known as El Niño, ocean temperatures in the Pacific are warmer than usual. This can lead to….

A

various weather extremes globally, including storms, droughts, and floods.

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48
Q

a new el nino is starting…true false>

A

true

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49
Q

ipcc report human influence has warmed the atmosphere, ocean and land? true or false

A

true

50
Q

what is the best estimate of human-caused global surface temperature increase? in degrees celcius

A

1.07 degrees celsius

51
Q

since at least 1970s, there has been persistent imbalance in energy flows that has led to….

A

excess energy being absorbed by different components of the climate system

52
Q

imbalanced energy is….

A

incoming solar energy and less outgoing energy due to greenhouse gases

53
Q

a stable climate: in balance would consist of…

A

incoming solar energy and outgoing energy

54
Q

forcing means..

A

Forcing refers to a disturbance or perturbation in the balance of energy in Earth’s atmosphere caused by external factors, such as changes in greenhouse gas concentrations.

55
Q

forcing definition in simpler terms..

A

In simpler terms, forcing is like poking a delicate balance, such as a seesaw, causing it to tilt temporarily. In response, the climate system adjusts to bring things back into balance, which can lead to changes in temperature, weather patterns, and other aspects of Earth’s climate.

56
Q

the Radiative Forcing due to observed CO2 increases (since 1750) due to human activity is about( w m-2) ..

A

2 W m-2.

57
Q

Radiative forcing leads to ….

A

a temperature change as the climate system tries to re-establish planetary energy balance

58
Q

resulting temperature change depends on ….

A

how big the radiative forcing is,
size of climate feedbacks
how long the radiative forcing is applied for

59
Q

A 2 W m-2 forcing, if applied for a sufficiently long time, would cause a surface warming of about…

A

1.6oC

Uncertainties in the size of climate feedbacks, which determine the “climate sensitivity” means the “likely” range is about 1.2 to 2oC

60
Q

climate drivers:

A

Greenhouse gases: carbon dioxide, methane, CFCs, ozone … more means warming
Tiny particles (“aerosols”): reflect or absorb sunlight; depending on their properties can cool or warm; very likely cool
Tiny particles: also modify cloud properties, making them reflect more sunlight; cool, possibly significantly
Others: e.g., forest  farmland, aircraft contrails – mixed impacts but likely small
Natural changes: sun’s variations, volcanic eruptions … either warm or cool
Internal (unforced) variability (“chaos”): either warm or cool

We must rule out causes as well as rule in causes

61
Q

changes in energy from the sum is a powerful driver of climate change. it can happen in two ways:

A

Changes in the amount of energy emitted by the Sun
Changes in the characteristics of the Earth’s orbit around the Sun

62
Q

while changes in TSI might seem significant, the actual impact on Earth’s climate is smaller once factors like …

A

absorption and reflection are taken into account.

63
Q

orbital parameters vary because of…

A

ellipse shape

tilt of the earths axis of rotation

timing we are closest to the sun occurs relative to the solstice

-By coincidence, we are in a period when the Earth’s orbit is close to being circular

64
Q

why do orbital variations matter?

A

they affect the seasonal distribution of radiation
E.g., if maximum tilt occurs when we are closest to the Sun, the Arctic gets more intense sunlight.

65
Q

“Milankovitch Effect” is a prime driver of ice ages - what it means….

A

means more winter snow and ice melt; glaciers and ice caps are less likely to form

At other times, glaciers and ice caps may be more likely to form

because of orbital variations which affect seasonal distribution of that radiation

66
Q

Explosive volcanic eruption: sulphur gases reach the stratosphere and form ….

A

sulphate aerosol particles; lifetime of around a year.

67
Q

what do sulphate aerosol particles cause?

A

negative forcing

68
Q

planetary albedo means…

A

Think of planetary albedo as the “reflectivity” of the Earth’s surface. Just like how some materials reflect light while others absorb it, Earth’s surface reflects some of the sunlight that hits it back into space.

Planetary albedo is a measure of how much of the Sun’s energy that hits the Earth is reflected back into space, compared to how much is absorbed by the Earth. It’s like a fraction or percentage that tells us how “bright” or “shiny” Earth looks from space.

For example, if Earth had a planetary albedo of 0.3, it means that 30% of the sunlight that hits Earth is reflected back into space, while the remaining 70% is absorbed by the planet’s surface.

So, in simple terms, planetary albedo is like Earth’s “brightness factor” from space—it tells us how much sunlight gets bounced back versus how much gets soaked

69
Q

Effusive volcanic eruptions: Sulphur gases and sulphate aerosol particles stay in …..

A

troposphere;

lifetime of ≈weeks. Little impact on climate

70
Q

Climate impact of eruptions depends on ….

A

amount of stratospheric sulphate aerosol

71
Q

The radiative forcing due to eruptions can be substantial (-2 W m-2) and have an observable effect on climate in the years immediately after it……
But the long-term effect of individual eruptions is small because of ….

A

the aerosol’s short lifetime compared to the climate response time – see earlier

72
Q

what is the most dominant anthropogenic radiative forcing mechanism (2.2 W m-2)?

A

CO2

73
Q

What are three major gases emitted by human activity what also occur naturally in the atmosphere?

A

CO2 CH4 AND N20 (NITROUS OXIDE)

74
Q

what is methane sometimes referred to as?in terms of long or short

A

long-lived and sometimes as short-lived

75
Q

is ozone o3 long lives or short lived?

A

classed as short-lived with tropospheric lifetimes of months

76
Q

methane sources

A

fossil fuel extraction and anaerobic environments

77
Q

methane lifetime?

A

around a decade

78
Q

what do methane increases lead to?

A

tropospheric ozone increases

79
Q

whats is the reason for recent methane growth rate?

A

could be increased anthropogenic sources

changes in its chemical destruction rate in the atmosphere

response of natural sources to climate change - feedback

80
Q

what shows success of international environment treaties?

A

chlorofluorocarbons outlawed by UN Montreal protocol to protect the ozone layer so production and emissions are now very low
but long lives gases so concentrations only slowly decrease

81
Q

what was chlorofluorocarbons eventually replaced with?

A

hydofluorocarbons

82
Q

what is the most significant contributor to negative radiative forcing?

A

aerosols

83
Q

what are aerosols

A

tiny particles emitted into the atmosphere by human activity or form in the atmosphere because of emissions of gases such as sulphur dioxide

84
Q

what are 2 contributors to aerosol concentrations?

A

sulphates and black carbon (Soot)

85
Q

when did sulphur concentrations peak?

A

in 1980s

86
Q

are aerosols short lived or long

A

short - a few weeks lifetimes

87
Q

what is aerosol-radiation interaction

A

the way aerosols affect incoming solar radiation

This depends on their size and their composition. Sulphate aerosols increase planetary albedo αp (by reflecting sunlight); black carbon aerosols decrease αp (by absorbing sunlight). The net effect is a negative forcing (i.e., increased αp)

88
Q

what are volcanic aerosols and what is the lifetime?

A

volcanic emissions reaching the stratosphere and have a lifetime of a few years

89
Q

aerosols are a a vital component in…

A

cloud formation

90
Q

ipcc radiative forcing figure emphasises that the net effect of human activity is positive forcing from what years?

A

1750-2019

91
Q

what percentage of emissions does methane contribute to

A

60 percent

92
Q

in the past decade burning coal, oil and gas has added how many units of CO2 each year to the atmosphere?

A

5 units

93
Q

what has removed half of the emitted c02

A

land and oceans! - great favour to us

94
Q

fossil fuel emissions started to dominate after… what year?

A

1950s

95
Q

what do model simulations indicate about the uptake of emitted c02? most of it is by …….. in the….

A

that most of it is by land in the tropics and mid- latitudes

96
Q

ocean uptake of c02 is highest in the… (what ocean)

A

southern oceans

97
Q

what country is the biggest c02 emitter

A

china

98
Q

what are the percentages of countries historically responsible for emissions

A

Although China is the biggest current emitter, it is responsible for “only” 13% of all historical emissions. USA is responsible for 25%, EU27 for 17% and UK for 5%

99
Q

what is the carbon budget?

A

i.e., how much CO2 we can emit to meet a given temperature target) …
this concept led to the concept of net zero

100
Q

what does warming depend on…… what emissions? what gas?

A

the cumulative emissions of c02

101
Q

how much c02 have we already emitted?

A

We have already emitted ≈2500 GtCO2; caused a warming of about 1.1 oC (Red)

102
Q

to meet the 1.5 degree target how much more can we only emit now?

A

To be reasonably confident of meeting a 1.5 oC target, we can only emit ≈500 GtCO2 more (Blue) This is the remaining “carbon budget”

103
Q

definition of net zero c02 emissions

A

IPCC defines this as the “… condition in which anthropogenic CO2 emissions are balanced globally by anthropogenic CO2 removals over a specified period”

104
Q

we need to be NEAR net zero by what year?

A

2050

105
Q

what is a strong hint from ice core record?

A

C02 is higher in warm period

106
Q

the land and ocean will continue to take up much of the CO2 we emit, but……. what will make this less efficient?

A

but climate change will make this uptake less efficient
this = positive climate feedback

107
Q

For long-lived greenhouse gases, the current radiative forcing comes from …..

A

emissions over the past century

108
Q

For shorter-lived gases, the current radiative forcing comes from ….

A

more recent emissions.

109
Q

a pulse of methane (perturbation lifetime of…..

A

12.4 years

110
Q

The UNFCCC Kyoto Protocol (1997) and Paris Agreement (2015) are multi-gas agreements which put limits on emissions of a groups of gases (Kyoto) or require parties to ….

A

declare their intentions to limit emissions of a group of gases (Paris)

111
Q

Multi-gas agreements require an…

A

exchange rate” to compare, e.g., a 1 kg emission of CH4 with a 1 kg emission of CO2

112
Q

what is the most commonly used metric called? - comparing c02 and non c02 emissions

A

100-YEAR GLOBAL WARMING POTENTIAL (GWP (100)

113
Q

whose choice was the metric of GWP 100 ?

A

GWP(100) is a UNFCCC choice not an IPCC one

114
Q

The so-called “basket of gases” covered by multi-gas agreements generally include:

A

CO2, CH4, nitrous oxide, hydrofluorocarbons and a few other minor gases
They do not include emissions of ozone depleting gases; these are controlled under the Montreal Protocol that protects the ozone layer

115
Q

what is a alternative metric to GWP and what does it offer in comparison?

A

Alternative metrics, like the Global Temperature Potential (GTP), offer a more accurate representation of the temperature impact of methane over shorter timeframes. Policymakers originally chose the 100-year timeframe somewhat arbitrarily, based on limited information available at the time. While GWP(100) isn’t perfect, it’s still commonly used, even as methane emissions continue to rise. However, it can be misleading when emissions remain constant or decline. Additionally, there are uncertainties surrounding the input parameters used to calculate GWP values, highlighting the complexity of accurately assessing the climate impact of different greenhouse gases.

116
Q

methane GWP100 varies in numbers from….

A

21 to 30

117
Q

how much is the estimated uncertainties in GWP values? percentage

A

30 percent depending on what gas

118
Q

for developed countries what gas dominates at what percentage?

for agriculture dominated countries what gas dominates?

A

For many developed countries, CO2 dominates; ≈20% from non-CO2

For agriculture dominated countries (e.g., Brazil and New Zealand) non-CO2 emissions dominate, and more one-third is from methane. Hence their CO2 equivalent emissions are highly dependent on metric choice

119
Q

what do ipcc reports say as time goes on?

A

blame humans more and more

120
Q
A

The Science of Climate Change (9 decks)

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