- Biology notes that will help international a level students prepare for their unit 4 exam.
- Consist of Chapter 5C: Environment and Climate Change.
- 95% types notes with the other 5% being hand written usually in tables.
- Useful tools to help learn and memorise them like emojis, diagrams...
, 1) Evidence for climate change
• Climate change is a long term change in the average weather patterns that have
come to define Earth’s local, regional and global climates
Often used to refer to global warming
Atmospheric carbon dioxide
• Carbon dioxide levels have always
fluctuated throughout time e.g
analysing the gas composition of
bubbles formed in ancient ice cores
(the deeper into the ice, the older it is)
• But ever since the Industrial
Revolution, CO2 levels have risen to
their highest in Earth’s history
Data shows a correlation between changing atmospheric CO2 levels and temperature
(other factors can affect it too like sun sport activity, solar winds)
-
Correlation does not equal causation but with the knowledge of CO2 as a
greenhouse gas, this is strong evidence that CO2 released by human activities is
causing an increase in global temperature
Average global temperatures
• Temperature records collected over extended periods of time can be put
together to show average global temperature change over time
• The hockey stick graph shows us an
in temperature after the 1800
(corresponds with the time where human
began burning fossil fuels)
There are many temp fluctuations but
overall = increasing
, Pollen grains preserved in peat bogs
Peat is an accumulation of partially decaying vegetation or organic matter that
becomes compacted under its own weight
it builds up in layers peat becomes older as you dig down
Peat core layers can be analysed to asses the pollen grains that are trapped in it
We can analyse the different plant species that were growing around the bog at
different point in time
Different plants grow under different climatic conditions so we can measure the
climate at the time
Dendrochronology
Tree trunks grow in diameter each growing season as they produce more vascular
tissue which forms rings
Light coloured rings =
Dark coloured rings =
Tress grows faster when conditions are warmer, so
wider rings = warmer years
Analysis of the width of tree rings can provide a
measure of climate each year of growth &
2) Anthropogenic climate change
1. Radiation form the sun hits earth and some is radiated back from the surface
2. Greenhouse gases absorb this re-radiated radiation, trapping it in the earth’s
atmosphere (=greenhouse effect), warming the earth
This is important to ensure that Earth is warm enough for life
Increasing levels of CO2 and methane are
entering the atmosphere as a result of
human activities leading to the enhanced
greenhouse effect
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