Earth's climate in the past Flashcards
Name 3 different methods of reconstructing past climates
Tree rings
Ice cores
Fossils
Marine sediments
Lake sediments
How do Tree rings show us past climates?
Tighter rings = dryer year
Wider/thinner rings can indicate temperatures, rainfall, and events such as avalanches, earthquakes and tsunamis
Large cells can mean the tree suffered frost damage
How do Ice cores show us past climates?
In Antarctica there is snow that contains CO2 and water vapour
The snow traps these gases for millions of years
scientists drill down into ice and gather ice cores (young ice at the top, older ice deeper down)
based on the concentration of gases in the ice, we can determine what years had high concentration of greenhouse gases (high temp years) and which had low concentration (low temp years)
in recent years, the ice has had a higher concentration therefore proving the increase of GHG
How do Fossils show us past climates?
similar to ice cores, scientists can drill into rock or coral and examine the powder to view the composition
More CO2 = higher temp years
some of the fossils predate Antarcticas data but they are also far more tampered with compared to the ice cores
How do marine sediments show us past climates?
examine microfossil shells that use oxygen when being created
If the shell contains a lot of light oxygen, then it must have been created during a warm climate as light oxygen is present in rain during warm climates
If it doesn’t, then light oxygen stayed on land as snow and therefore it was a cold climate
How do Lake sediments show us past climates?
Pollen from thousands of years ago is trapped under swamp mud
mud cores can be created and searched for pollen
this pollen can tell scientists about the plants in the past and how if they were suited to high or low temp climates
the pollen can also tell us if plants were subject to droughts or other events and even if the population was shrinking or growing
What are the Milankovitch cycles?
Eccentricity - change in orbit of the earth around the sun - 100,000 years
Precession - wobble of the Earth on its axis - 26,000
Axial tilt - tilt of the Earth’s axis - 41,000 years
How do the Milankovitch cycles affect the climate?
Orbit - a more oval orbit causes the Earth to be closer/further from the sun at certain times during it’s orbit causing temperature differences and potential glacial periods
Wobble - the way that the Earth gyrates can shift the point on the Earth that is closest to the sun which causes seasonal differences. This can cause summers to be cooler and result in glacial periods
Tilt - alters the suns focus which can also cause seasonal differences and therefore more glacial periods
How has global climate changed over the last 100 million years?
100 mya - it was 8 degrees hotter and there were 5x the carbon levels
35 mya - dropped to lower than modern temps
300 years ago - temps increase due to human enhanced climate change - 9/10 hottest years on record were between 2013 - 2021
