Evidence For Climate Change Flashcards
What is climate change?
Any significant change in the weather of a region over a period of at least several decades, e.g increasing average temperature or rainfall, or a change in the usual wind direction.
Long term climate change patterns
Temperatures have been much higher at some points in the past than they are today.
Over last 400,000 years there is fluctuations, climate shifted between cold glacial periods- lasting around 100,000 and warmer interglacial periods that lasted around 10,000 years- we’re in an interglacial period now.
Medium term climate change patterns
The last glacial period ended around 18,000 years ago.
The warming of the climate after this was fast at times, but it wasn’t constant- about 13,000 years ago the climate switched back to cooler conditions for about 1000 years.
Around 5000 years ago, temperatures were 1-2 degrees higher than today.
Short term climate change patterns
Global warming is the term used for the rapidly increasing global temperature over the last century.
Overall pattern = general increase in temp but pattern inconstant.
Global temp rose steadily from early 20th century until 40s (although they fluctuated annually), then dropped back down.
How do ice cores provide evidence for long term climate change?
1) Drill deep into ice sheets to extract cores- sheets are made of layers- one every year (ice at bottom very old).
2) Analysis of gases trapped- tells temp each year.
How does pollen analysis provide evidence for long term climate change?
1) Pollen from plants is often preserved in sediment.
2) The preserved pollen can be identified and dated.
3) Scientists know conditions plant lives in now
How does sea level change provide evidence for long term climate change?
1) Sea level is affected by things like the volume of water stored as ice.
2) Past sea levels are shown by raised beaches (formed when sea levels were higher). Raised beaches can be dated. They can indicate that less water was stored as ice (so it was warmer).
How do historical records provide evidence for medium term climate change?
Historical records can indirectly indicate different conditions in the past. E.g agricultural reports (such as harvest times) show changing conditions throughout human history.
How do tree rings provide evidence for medium term climate change?
1) A new tree ring is formed each year as a tree grows. If conditions that year were good the tree ring produced will be thick.
2) Scientists can take cores and count rings to find age. Thickness = climate
3) Tree rings can reliably show and date climate conditions up to 10 000 years ago.
How do retreating glaciers provide evidence for medium term climate change?
1) Scientists can tell how big a glacier was and how far it extended by looking at the position of the rocks deposited by it. These rocks can be dated.
2) Distance of rocks from the current glacier indicates climate change. E.g if the front of the glacier is now miles away from the rocks it indicates that temperatures have increased over that period of time.
How do weather records provide evidence for short term climate change?
1) Details of weather conditions have been consistently collected since 1861.
2) These can be used to show detailed climate changes over the short time period they’ve been collected
How does polar ice melt provide evidence for short term climate change?
1) Current research into the behaviour of polar ice shows a reduction in the amount of ice at both poles.
2) Changes in the extent of polar ice shows changes in the climatic factors affecting them, e.g increased melting shows increased temperatures.
How do ecosystem changes provide evidence for short term climate change?
Changes in temperature affect the availablity of food and shelter. This affects what species live in an area. So scientists can use changes in how species are distributed to indicate changes in the climate.
