Climate Change Science Defenitions

Recent temperature trends

Land regions warmed faster than oceans in High latitudes of Northern hemisphere

Recent warming of oceans - all latitudes

Seasonal trends in temperature

Greatest warming in spring and winter in N. Hemisphere

Why is Antarctica less affected by temperature change than the Artic

Arctic is an ocean covered by sea ice

Antarctica is an elevated continent covered in more permanent ice and snow

Trends in precipitation

Strong negative correlation between precipitation and surface temperatures

Increases north of 30°

Downward trend in the tropics

Specific heat

air temperature (linked to a detectable temp change)

Latent heat

linked to water vapour (phase change)

Atmospheric circulation changes

Pole ward shift of Atlantic and southern polar jet

Increased and pole ward shift in NH winter storm-track activity

Increased storm activity in the extra-tropical HC

Future changes

Increase in the global mean temperature, Greatest degree of warming at high latitudes

Prediction of global increases in mean precipitation, Increased precipitation at high latitudes - less in the sub tropics

Temporal variation – increases at high latitudes pronounced in winter

IR Adsorption

How much light is absorbed due to gas presence

Ring down

How much light disappears once the light source is removed

Why did we switch to ring down?

It was more accurate

Which wavelength of UV is completely adsorbed by ozone

UV C (100-280nm) the shortest

Atmospheric window

The wavelength range not absorbed by Earth’s atmosphere.

Radiation balance of the earth

Amount of heat absorbed = heat radiation emitted

Radiative forcing (W m^-2)

The influence a given climatic factor has on the amount of downward-directed radiant energy impinging upon Earth’s surface.

Radiative efficiency (W m^–2 ppb^–1)

The capacity of each molecule to absorb long IR radiation

Global warming potential (GWP)

Ratio of the time-integrated radiative forcing from the instantaneous release of 1 kg of a trace substance relative to that of 1 kg of a reference gas (CO₂)

GWP rankings

N₂O = 310 > CH₄ = 21 > CO₂ = 1

GWP Formula

TH is the time horizon over which the calculation is considered

a_x is the radiative efficiency due to a unit increase in atmospheric abundance of the substance (i.e., Wm^-2 kg^-1)

[x(t)] is the time-dependent decay in abundance of the substance following an instantaneous release of it at time t=0.

The denominator contains the corresponding quantities for the reference gas (i.e. CO₂) Which always has a GWP of 1.

Dipole moment

Tension between a positive and negative pole within the molecule

Molecular vibrations

To absorb IR the electric dipole moment of the molecule must change when electrons are displaced

In order to be IR active the stretching of a molecule must be

Asymmetric

v1

stretching

v2

bending motion

v3

asymmetric stretch

What creates the dipole moment

v2 and v3

Electronic transition

Energy level where molecule can partake in reactions due to having adsorbed enough energy

Vibrational transition

Energy level when Bonds in a molecule start to vibrate

Rotational transition

Energy level where molecules start to rotate

Ranking of energy levels

Rotational transition<Vibrational transition<Electronic transition

Formula for GHG lifetime

τ = 1 / k’

k’

[OH] is the pseudo 1^st order rate constant. times concentration of GHG

Why is the formula pseudo first order?

Because we can say [OH] is constant due to its abundance.

Reactions that remove GHGs

CH₄ + OH → CH₃ + H₂O (followed by a chain of reactions in the troposphere)

O₃ + hv → O₂ + O (tropospheric photolysis)

O₃ + OH → HO₂ + O₂ (stratosphere)

N₂O ® N₂ → O (stratospheric photolysis) – major sink for N₂O 

Reactions in the bio(geo)sphere

CO₂, photosynthesis, carbonate formation

CH₄ methane oxidation CH₄ + O₂ → CO₂ and H₂O

Effectors of ERF

Solar and Albedo

Effect solar has on ERF

0.1%

Albedo changers

Change in land use, Black Carbon (soot) on snow causes, Aerosols, Volcanism

Effect of change in land use on albedo

Varies (Deforestation: increase, Urbanisation: decrease)

Effect of black carbon/soot on albedo

Lower reflectance: + 0.06 W/m2

Effect of aerosols on albedo

Can scatter/absorb solar radiation (- 0.45 W/m2) and act as cloud condensation nuclei: more clouds for longer period.

Effect of volcanism on albedo

Add to aerosols in quick high bursts which result in large dips in ERF. Though high levels of CO2 have resulted in a decrease in effect.

Climate (Climate data context)

Temperature (and CO2)

Categories of historical climate data

Instrumental records, The past c. 1000 years, Long-term variability on any timescale over which reliable data can be obtained

Difficulties with instrumental data

Errors, Calibration – the increase over 150 years has only been approx. 0.8 C.

Uniformitarianism

The idea that the Earth was shaped by the same natural processes still in operation today, operating at similar intensities. (Such as how glaciers behave like growing and shrinking)

Representative Concentration Pathways (RCPs)

SSP1-2.6 - Sustainable pathways, SSP2-4.5 - Middle-of-the-road, SSP3-7.0 - Regional rivalry, SSP5-8.5 - Fossil fuel-rich development, Plus SSP1-1.9 - 1.5°C Paris Agreement goal

Eccentricity

The shape of Earth's orbit

Obliquity

The angle that Earth's axis is tilted with respect to Earth's orbital plane

Precession

The direction that Earth's spin axis is pointed

Frequency of Eccentricity change

~100 kyr, with ‘supercycle’ every 413 kyr, nearly circular (low eccentricity e = 0) to slightly oval (high eccentricity e = 0.06)

Frequency of Obliquity

22° to 24.5° every ~ 41 ka.

Frequency of Precession

A cycle of approximately 22,000 years

Implications of greater climate variability on freshwater flow

Increasing in the Arctic,

Earlier spring peak flows (By 1 month)

Increased winter base flows (Northern Hemisphere, snow fed river basins)

Decreased summer flows

Increased climate variability’s effect on lakes

Warming, Increases/decreases in lake levels, Reduction in ice cover (including time), Changes in net water availability, (precipitation – evaporation) determined by changes in river inflows and balance between precipitation and evaporation.

Non-climatic stressors on freshwater systems

Water pollution, damming of rivers, wetland drainage, reduction in stream flow and lowering of the water table.

Fraction of water use taken by irrigation

About 90%

2026 Government Promises about freshwater

£104 billion of private investment

Water Special Measures Act to strengthen accountability

Banned unfair executive bonuses

Made pollution cover-ups a criminal offence