The last glacial period ended 15,000 years ago and since then the climate has been warming. Global warming is the term used to describe the sharp rise in global temperatures over the last century and is a type of climate change. Evidence of climate change: Modern evidence (temperature records): Climate change is the long-term change in the weather Occurs over thousands of years Earth’s average surface air temperature has increased by approximately 1 degree Celsius over the last 100 years – Sea-levels have by 19cm since 1900 due to thermal expansion and ice sheets melting temperatures are the warmest they have been since 1850 World’s glaciers and ice sheets are decreasing in size Antarctica loses 134 billion tonnes per year Past evidence: TREE RINGS: ICE CORES: FOSSIL As a tree it Ice sheets are made SEDIMENTS: POLLEN: forms a new ring up of layers of ice – Pollen from plants – each year the tree one layer is formed The remains of gets preserved in rings are thicker in each year. organisms found sediment, e.g. at the warm, wet in cores taken bottom of lakes or in conditions. Scientists drill into from ocean peat bogs. ice sheets to get sediments can Scientists take long cores of ice. also be analysed. Scientists can cores and count the identify the rings to find the By analysing the These can preserved pollen to age of a tree. The gases trapped in the extend the show which species thickness of each layers of ice they temperature were living at that ring show what the can tell what the record back at time. climate is like. temperature was least 5 million each year. years. Scientists know the Tree rings are a conditions that reliable source of Oxygen isotopes Plankton can plants live in now, so evidence of climate (the amount of reveal preserved pollen change for the past oxygen in the ice) information such form similar plants 10,000 years are used to estimate as past surface shows that climate temperatures. water conditions were temperatures similar. One ice core and levels of
The last glacial period ended 15,000 years ago and since then the climate has been warming. Global warming is the term used to describe the sharp rise in global temperatures over the last century and is a type of climate change. Evidence of climate change: Modern evidence (temperature records): Climate change is the long-term change in the weather Occurs over thousands of years Earth’s average surface air temperature has increased by approximately 1 degree Celsius over the last 100 years Sea-levels have by 19cm since 1900 – due to thermal expansion and ice sheets melting temperatures are the warmest they have been since 1850 World’s glaciers and ice sheets are decreasing in size Antarctica loses 134 billion tonnes per year Past evidence: TREE RINGS: As a tree it forms a new ring each year – the tree rings are thicker in warm, wet conditions. Scientists take cores and count the rings to find the age of a tree. The thickness of each ring show what the climate is like. Tree rings are a reliable source of evidence of climate change for the past 10,000 years ICE CORES: Ice sheets are made up of layers of ice – one layer is formed each year. Scientists drill into ice sheets to get long cores of ice. By analysing the gases trapped in the layers of ice they can tell what the temperature was each year. Oxygen isotopes (the amount of oxygen in the ice) are used to estimate temperatures. One ice core SEDIMENTS: The remains of organisms found in cores taken from ocean sediments can also be analysed. These can extend the temperature record back at least 5 million years. Plankton can reveal information such as past surface water temperatures and levels of FOSSIL POLLEN: Pollen from plants gets preserved in sediment, e.g. at the bottom of lakes or in peat bogs. Scientists can identify the preserved pollen to show which species were living at that time. Scientists know the conditions that plants live in now, so preserved pollen form similar plants shows that climate conditions were similar.
AQA_GCSE_Geography_Paper_1_Revision_Guide_2018(4).docx