Lesson 9-What are the natural and human changes in the carbon cycle? Flashcards
How has climate changed over time?
- Over the past 2.6 million years global climates have fluctuated between interglacial (warm) and glacial (cold) periods
- Data from Antarctic ice core samples, show temperatures and carbon dioxide levels correlate
- Higher temperatures mean high concentrations of carbon dioxide in the atmosphere
Earths climate history
- The last 2.6 million years are theQuaternaryperiod when there have been 60 cold periods and warmerinterglacialperiods
- The lastice ageended approximately 25,000 years ago
Why has the climate changed over time?
- CO2 is a greenhouse gas, this means more solar radiation is kept in our atmosphere and less escapes back to space.
- This is known as enhancing the natural greenhouse effect
- Instead of increased CO2 causing temperature increase, temperature increase can cause more CO2 to go into the atmosphere due to melting of the permafrost releasing methane (positive feedback loop)
How does increasing temperature effect the carbon cycle?
Permafrost melts:
- Hotter temperatures mean decomposition happens as permafrost melts
- This means more carbon goes into the atmosphere (positive feedback loop) as carbon is a greenhouse gas
- Which causes further warming and further permafrost melting
Increased Plant growth: - Warmer temperatures cause increased plant growth so more carbon stored in biosphere
Ice Melts:
- Warmer temperatures mean less carbon stored in ice so less in cryosphere and more in hydrosphere.
How does decreasing temps effect the carbon cycle?
Colder oceans:
- Cold water can hold more carbon than warm water therefore when it’s cold more carbon held in hydrosphere
Colder Atmosphere:
- Less plants when its colder therefore reduced photosynthesis and respiration and less carbon held in biosphere
- Less decomposition when its colder so more carbon held in permafrost therefore less goes into atmosphere
Ice forms:
- Less water when it’s cold as more in ice therefore less sediment being moved by rivers into oceans so less pedosphere hydrosphere transfer of carbon
How can climate change naturally?
- Milankovic cycles
- Wildfires
- Volcanic eruptions
How can the climate change naturally-Milankovic cycles
- Milankovitch cycles are changes in the Earth’s movementschanging its climate over thousands of years
- Milankovitch suggested that variations in eccentricity, tilt, and wobble of the Earth’s orbitcreating cyclic changes in the amount of solar radiation reaching the Earth
- Changing climate over 1000s of years
What are the physical causes in the change in the carbon cycle- Milankovic cycles
- Eccentricity (shape)
- Obliquity (tilt)
- Precession (wobble)
What are the physical causes in the change in the carbon cycle- Milankovic cycles
- Eccentricity (shape)
- 100,000
- The Earth iscloser to the Sun in January than in July, meaning the seasons are more extreme in the Southern Hemisphere than in the Northern Hemisphere. Resulting in the northern hemisphere receiving roughly 7% less radiation in the summer, and 7% more in the winter, than the southern hemisphere because the Earth is closer to the Sun in January than in July
What are the physical causes in the change in the carbon cycle- Milankovic cycles
-Obliquity (tilt)
- 41,000
- If the Earth’s axis were vertical, there would be no seasons – the same part of the Earth’s surface would be facing the Sun throughout the year.
-The more angled the axis, the more extreme the seasons. Currently, the Earth is tilted at 23.44°, which is halfway between its maximum (24.5°) and minimum (22.1°) tilt and this angle is on the decreasing cycle
What are the physical causes in the change in the carbon cycle- Milankovic cycles
-Precession (wobble)
- 26,000
- The axis wobbles andhas a 26,000-year time period.
- This due to the tidal forces exerted by the Sun and the moon on the Earth, It changes which star we see as the North Star – currently it is Polaris, but 13,000 years ago, it would have been Vega
So how significant are orbital changes in changing Earth’s climate-Milankovic cycles
- The impacts of orbital change on insolation is small (±0.5°C)
- However its overall effect is enough to ‘tip’ the climate into a major change (5-7°C colder)
- This is due to Positive feedback mechanisms
What are the physical causes of change in the carbon cycles- Wildfires
More carbon in the atmosphere:
- Burning transfers carbon from the biosphere to the atmosphere as CO₂
- Extreme wildfires can turn vast areas from being carbon sinks to being a carbon source
- Warmer temperatures meansmore wildfires (EG 2019 Arcticwildfires which emitted 50megatons of CO2 into theatmosphere which is more than2010-2018 combined)
Encouraging plant growth:
- Burning can encourage the growth of plants in the long term and some plants need wildfires to grow (pyrophytic plants)
What are the physical causes of change in the carbon cycle-Volcanic activity
- Carbon, stored in rocks for millions of years, is released, as CO2 gas, to the atmosphere through volcanic eruptions
- This varies over time (temporal change):Volcanic activity hasn’t stayed the same throughout time - during the Palaeozoic era, between 542 and 251 million years ago, volcanoes were more active than now releasing more CO2 into the atmosphere
- Today, between 130 and 380 million tonnes of carbon dioxide is released annually through volcanic activity (much less than 30 billion tonnes from human activity)
So how significant are volcanic eruptions in changing Earth’s climate
- The USGS says volcanic activity has never caused significant atmospheric warming
- This is because CO2 released is counteracted by Sulphur dioxide which forms particles which block the sunlight / reflect it back into space.
- Volcanoes have released less than 1% of all atmospheric CO2.
