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Y2 Climate Change Science > Recent and Long Term Changes in Climate > Flashcards

Recent and Long Term Changes in Climate Flashcards

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1
Q

IPCC reports creates a synoptic review of the current research on climate change
What is the purpose of this report?

A
  • To advance scientific knownledge about climate change caused by human activities examines all the relevant scienfic litrature
  • Including natural, economic and social impacts and risks
  • Contains projected changes in temperature, precipitation, droughts, sea levels, arctic sea ice etc
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2
Q

Define Climate

A

Average weather conditions in a particular area, over a particular time period
(temperture, precipitation, radiation, wind speed, humidity - long time scale)

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3
Q

Define Weather

A

Atmospheric conditions in a particular area, over a particular time
(temperature, precipitation, radiation, wind speed, humidity - shorter time scale)

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4
Q

What is climate change?

A

Changes in average weather in a particular area, over time

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5
Q

What is the relevancy of timescales to climate change?

A

Needs to be long enough to be a sensible average, and short enough to be relevant to animals (including humans) and plants

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6
Q

What is the Earth-Atmosphere energy balance?

A
  • The balance between incoming energy from the Sun (shortwave) and outgoing energy from the Earth (longwave)
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6
Q

When the radiation flux is out of balance….

A

It causes the climate to change

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7
Q

Here is a list of ERF values
What does ERF quantify?

A

The effect of a process of Earth’s energy balance, relative to 1750 pre-industrial baseline
It’s a globally average value expressed in W/m²

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8
Q

Why can solar insolation change (longterm)?

A
  • Changes in insolation caused by changes in the Earth’s orbit/axis (10-100ka cycles)
  • Called the Milankovitch cycles (change ±20%)
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9
Q

Why can solar insolation change (shorterm)?

A
  • Sunspots caused by changes in the magnetic pressure on the surface of the sun in association with decreases in the surrounding atmospheric pressure
  • 11-yr cycles
  • The warmer area around the sport gives out increased radiation, hence warming
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10
Q

How has land cover affected albdeo of this surface?

A
  • Darker forest vs lighter crop lands (due to deforestation)
  • Resulted in colour of the surface to change
  • Hence more light would be refleced on the lighter side, leading to a cooling effect
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11
Q

How has land cover affected albedo on this surface?

A

The black within the glacier is due to soot, which has been depoitted into the glacier
Results in increased absorption due to darker colour (warming effect)

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12
Q

Which are the main 3 gasses which contribute towards global warming?

A

CO₂, CH₄, N₂O

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13
Q

How can aerosols affect clouds?

A

Aerosols can scatter/absorb solar radiation AND act as cloud condensation nuclei: more clouds for longer period

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14
Q

Name some natural aerosols

A
  • Dust
  • Sea Salt
  • Sulphate from volcanoes
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15
Q

What are some Anthropogenic sources of Aerosols?

A
  • Biomass burning
  • Sulphate from fossil fuel burning
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16
Q

What affect do volanoes have on climate?

A
  • The increased debris and dust from a volcanic explosion will have a negative albdeo affect
  • Meaning more light is reflected and there will be cooling
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17
Q

“Climate” in this context generally means temperature (and CO₂)
There are 3 main categories of timescales
What are they?

A
  • Instrumental records (350yrs max, but genrally less than 150yrs)
  • The past c.1000yrs (tree-rings, ice-cores etc)
  • Long-term variability on any timescale over which reliable data can be obtained (Lake sediments, ice cores, fossils etc)
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18
Q

John Tyndall (1860) discovered…

A

That different GHG will produce different amounts of warming measured by his radio spectrophotometer

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19
Q

What is the Keeling Curve?

A
  • Daily measurements of CO₂ taken at the Mauna Loa Observatory in Hawaii
  • Daily fluctuations due to photosynthesis ceasing in the nightime
  • Record goes back to 1958
20
Q

When was the first temperature record (Central England Temperature) compiled by Gordon Manley

A

In 1974

21
Q

many intrumental temperature records can look like this due to background noise, and hence it can be difficult to observe any pattern
How can this be overcome

A
  • By selecting a reference year (or period which has been average)
  • And subtracting it from each annual temperature measurements
  • Hence allows a trend to be worked out like this
22
Q

What is the issue with past temperature data which has been measured using thermometers?

A
  • Hard to read thermometers to an accurate degree (e.g. there has only been 0.8°C warming in past 150yrs)
  • Different countries may have different resources and different ways of doing things
  • Hence need for standardisation is important
23
Q

Why is random error tolerable but systematic change not in records

A
  • Radom error are tolerable, if you have a long enough record to make good averages (anomalies can be spotted easily)
  • Systematic changes over time must be identified and corrected if possible e.g. Urban heat island effect
24
Q

What are two ways to measure the Urban Heat Island effect

A
  • Thermal Remote Sensing - how much heat is reflected from the surface, red is warmer and blue is colder
  • False colour composite - uses IR which will be particularly absorbed by vegetation, where there is more vegetation is will be cooler
25
Q

This graph shows the changes in annual surface temperature, between 1901-2023
What is the key trend?

A
  • That there is more warming in the N.Hemisphere - especially at the poles
  • Increased warming over land rather than oceans
  • This trend is seen more greatly in recent yrs however
26
Q

How has the likely range of total human-caused global surface temperature increased from 1850-1900 to 2010-2019 changes?

A

Increased from 0.8°C to 1.3°C

27
Q

Internal variability changed global surface temperature from 1850-1900 to 2010-2019

A

-0.2°C to +0.2°C

28
Q

Why is the is great deal of studing done into past climate change?

A
  • Future climate change is unknown, but past climate change is recorded in the world around us
  • By understanding archives of past climate change, we can increase our understanding of current climate change
29
Q

Charles Lyell (1797-1875) came up with the theory of Uniformitarianism
What does it involve?

A
  • The idea that the Earth was shaped by the same natural processes still in operation today, operating at similar intensities
  • Pioneering explanation of climate change, in which shifting boundaries between oceans and continents could be used to explain long-term variations in temperature and rainfall
30
Q

What is Palaeoclimatology?

A
  • The study of past climates that have existed during Earth’s different geological ages
31
Q

What is a direct way in which past atmospheres can be studied?

A
  • Can use fossilised air from bubbles within ice cires, to work out what past atmospheric air composition was like
32
Q

What is the indirect way we can study past atmospheres and climate?

A
  • Through using proxies
33
Q

So how are the Palaeoarchives used?

A
  • The Earth system has and will continue to respond to various forcings (volcanic, solar and orbital) and to changes in atmospheric composition
  • Palaeoclimate data and models provide quantitative information on how the Earth system responsed to these perturbations
  • Enables understanding of feedbacks over longer timescales
34
Q

What are some core proxies used to measure climate over the past c. 1000yrs

A
  • Tree rings (rates of growth and ring densities)
  • Coral composition (elemental ratios)
  • Peatland (oxygen isotope ratios, pollen)
  • Sediment composition (fossils, isotopes, chemistry)
35
Q

The following graph shows the different types and geographic location of proxies measuring back c. 2000yrs
What is the key issue shown?

A

The N.Hemisphere is very heavily sampled compared to the S.Hemisphere
Hence may create knowledge gaps

36
Q

Name some key climate events over the past 12kys?

A
  • Interglacial-Glacerial transition - including the Bolling Allerod and Younger Dryas events
  • Rapid warming at 11.7ka due to leaving the last glacial
  • Natural Fluctuations including: 8.2 event, MWP and LIA
  • Current contempory warming
37
Q

What causes the changes between Glacial and Interglacial periods

A
  • Driven by changes in insolation due to Milankovitch cycles
38
Q

The most accurate climate data from the past 1.5 million years has come from…

A

Ice cores from Antarctica and Greenland
Through measuring both atmospheric gases which are trapped in the ice and also the elements/isotope compositions within the ice

39
Q

What are the 3 different types of Milankovitch cycles?

A
  • Eccentricity
  • Obliquity
  • Precession
40
Q

What is Eccentricity?

A
  • shape of Earth’s orbit
  • It can vary from being nearly circular (low eccentricity) to slightly oval (high eccentricity)
  • Changes every ~100kyr, with a ‘supercycle’ every 413 kyr
  • More ellipitcal = cloeser to sun = more ice melting = interglacial
41
Q

What is Obliquity?

A
  • the angle that Earth’s rotational axis is tilted with respect to Earth’s orbtial plane
  • varies from 22°-24.5° every ~41ka
  • Affect amount of energy received by largest landmass (N.Hemisphere)
  • Greater tilt = greater N.Hemisphere summer warming/melting
42
Q

What is Precession?

A
  • ‘wobble’ of the earths axis
  • Changes moment when N.Hemisphere is pointing towards the Sun
  • Effectively changing N.Hemisphere summer into winter and S.Hemisphere winter into summer
  • Cycles of 22kyrs
43
Q

Which cycle is the main driver of temperature variations over the past c.1 Myr

A

Eccentricity cycle

44
Q

What is the significance of models and how do they work?

A
  • They are an important tool for understanding past, present and future climate change
  • Based on fundamental laws of physics of the atmosphere, ocean, ice and land
  • Calculations on a three-dimersional grid made of ‘gridcells’ of about 100km across
45
Q

How can we evalute the performance of climate models?

A

By comparing historical climate model simulations to observations
(model predictions in recent yrs have gotten a lot more reliable and consider additional factors like aerosols, carbon cycles, vegetations, atmospheric chemistry and land ice etc )

46
Q

What are the main Representative Concentration Pathways (RCPs)

A
  • SSP1-2.6 - sustainable pathways
  • SSP2-4.5 - middle of the road
  • SSP3-7.0 - Regional rivalry
  • SSP5-8.5 - Fossil fuel-rich development
47
Q

What 4 key indicators of the climate system may be affected by future (and current) climate change?

A
  • Global surface air temperature (increase)
  • Global ocean heat content and thermosteric sea level (increase)
  • Arctic September sea ice area (decrease)
  • Global land precipitation (increase)
48
Q

What 4 changes may occur within our oceans due to future/current climate change?

A
  • Marine heatwaves (increase)
  • Dissolved oxygen (decreased)
  • AMOC (slowdown)
  • Ocean acification

Y2 Climate Change Science (8 decks)

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