Evidence for Climate Change:
● Climate change = long-term change in Earth’s climate
○ Could be due to an increase in the average atmospheric temperature
● Quaternary period = period of geological time from 2.6 million years ago to the present day
○ Period marks a time when there was a global drop in temperature (ice age)
○ Period is split into 2 epochs
■ Pleistocene epoch → 2.6 million years to 12,000 years
■ Holocene epoch → 12,000 years to present day
○ Entire period is often called an ice age due to permanent ice sheet on Antarctica
● We live in the Holocene epoch, during the current interglacial episode (climate is relatively warmer and stable)
○ Glacial episode = colder period of time with ice expansion/ more ice → lasts 100,000 years
○ Interglacial episode = warmer period of time with less ice → lasts 10, 000 years between 2 glacial
periods
Evidence of climate change:
● Global climate change occurs slowly over 1000s of years but has only been reliable since 1914
○ Earth’s average surface air temperature has increased by 1°C over the last 100 years
○ Sea levels have risen by 19 cm since 1900
■ Due to thermal expansions and melting ice sheets
○ World’s glaciers/ice sheets are decreasing in size
■ eg/ NASA data shows that since 2002, volume of ice lost in Antarctica is 134 billion tonnes per
year
○ Ocean temperatures have been increasing since 1850
● Before reliable data records/modern technology, proxy data was used ( natural recorders) → not reliable
○ eg/ ice cores
■ The deeper the snow, the older the snow → can be drilled and analysed
■ Oxygen isotopes in ice cores are used to estimate how temperature has changed
● Ratio of 2 types of oxygen isotopes are measured to work out what the climate was
like
■ When ice cores are melted , trapped CO 2 and methane are released
● Amount can be compared to present day levels → shows differences in climate
○ eg/ ocean sediments
■ The deeper the sediment, the older the sediment
■ Organisms/remains of plankton in the sediment reveal information about climate change
● eg/ past surface water temperatures, levels of oxygen and nutrients