L4 - Observational evidence and uncertainties for climate change Flashcards

1
Q

When did water vapor condense to form oceans?

A

3.3 BYA

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2
Q

What was the first form of life to develop oxygen?

A

Photosynthetic cyanobacteria in shallow waters, around 3 BYA

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3
Q

What process contributed to the development of atmospheric oxygen 3 BYA?

A

Photosynthesis from blue-green algae (3 BYA) and green plants (2 BYA)

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4
Q

What is the chemical equation for photosynthesis?

A

nCO₂ + nH₂O → nCH₂O + nO₂

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5
Q

What is the photo-dissociation of water?

A

2H₂O + hv → 2H₂ + O₂

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6
Q

What major atmospheric change occurred 1.6 BYA?

A

Oxygen levels reached 1% of today’s levels, leading to ozone formation, which protected life from UV radiation.

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7
Q

What are the current percentages of major atmospheric gases?

A

Nitrogen (N₂): 78%
Oxygen (O₂): 21%
Argon (Ar): 0.93%
Carbon dioxide (CO₂): 0.03%
Methane (CH₄): 0.0018%
Water vapor: 0.2% - 2.6% (variable)

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8
Q

What did John Tyndall propose in 1863 about atmospheric heat?

A

The atmosphere allows solar heat to enter but prevents some of it from escaping, leading to heat accumulation.

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9
Q

What instrument did Tyndall use to study atmospheric gases?

A

A spectrophotometer to measure the electromagnetic spectrum.

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10
Q

What gases did Tyndall identify as absorbing heat?

A

Water vapor (H₂O) and carbon dioxide (CO2)

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11
Q

By how much have greenhouse gas concentrations increased since 1800?

A

CO₂: 35% increase
Methane (CH₄): 142% increase
Nitrous oxide (N₂O): 18% increase

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12
Q

How do scientists measure past atmospheric gas concentrations?

A

By extracting gases from bubbles trapped in ice cores.

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13
Q

What is the Keeling Curve?

A

The longest unbroken record of atmospheric CO₂ concentrations, showing seasonal variations.

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14
Q

What historical trend does the Keeling Curve show?

A

CO₂ concentrations have increased by 39% since 1750, peaking at 400 ppmv.

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15
Q

Why is the CO₂ increase considered man-made?

A

CO₂ from fossil fuels contains no ¹⁴C, unlike natural atmospheric CO₂.

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16
Q

What percentage of CO₂ emissions in the past 20 years came from fossil fuels?

A

75% from fossil fuels, with the remainder from deforestation and land use changes.

17
Q

How much anthropogenic CO₂ has the ocean absorbed?

A

30% of emitted CO₂, causing ocean acidification and a 0.1 decrease in pH.

18
Q

How do tree rings provide climate data?

A

They reflect water availability and record changes over 10,000 years.

19
Q

How do ice cores provide temperature records?

A

They contain oxygen isotopes and trapped air bubbles that reveal past temperatures up to 800,000 years ago.

20
Q

What does ocean sediment reveal about past temperatures?

A

The proportion of heavy oxygen isotopes in seashells increases when temperatures drop.

21
Q

How does CO₂ concentration correlate with temperature change?

A

There is a clear correlation over the last 160,000 years

22
Q

How has the CO₂ level changed in the last 420,000 years?

A

It is currently outside the natural variability range.

23
Q

What factors contribute to climate variability?

A

Solar variation
Volcanic activity
Internal climate variability
Human-induced CO₂ and aerosols

24
Q

How many temperature observations are recorded monthly?

A

1.5 million global observations.

25
Q

When did satellites start providing temperature data?

26
Q

What natural events temporarily alter global temperatures?

A

El Niño: Causes warming (e.g., 1998 spike).

La Niña: Causes cooling (e.g., 1999-2000 dip).

Volcanic eruptions: Cause temporary cooling (e.g., Mount Pinatubo, 1991).

27
Q

What is the trend in global mean temperatures?

A

Rising faster over time, with 2015-2024 being the warmest years on record

28
Q

How much has sea level risen since 1900?

29
Q

What are the main contributors to sea level rise?

A

Glacier melt (Greenland, Alaska, Arctic)

Thermal expansion of seawater

30
Q

What was the sea level rise rate from 1961-2003?

A

1.8 mm per year

31
Q

What was the sea level rise rate from 1992-2003?

A

3.1 mm per year

32
Q

What regions are most vulnerable to sea level rise?

A

Norfolk (UK), Netherlands, Bangladesh, Florida.

33
Q

What conditions are required for a hurricane to form?

A

Warm ocean water (energy source)
Converging winds forcing air upward
Humid rising air creating storm clouds

34
Q

How has total hurricane damage changed in the U.S.?

A

1980-1994: $100 billion
1995-2009: $475 billion
2010-2024: $800 billion

35
Q

What trend has been observed in hurricane wind speeds since 1980?

A

Consistently increasing.

36
Q

How has extreme precipitation changed over time?

A

Once-a-year precipitation events increased by 25-100% in the Great Plains.

Two-day precipitation events have become more frequent since the 1960s.