Evidence For Climate Change Flashcards
Is climate change staying the same or changing
Constantly changing
What is climate change
Any significant change in the weather of a region over a period of time of at least several decades
Eg. increasing average temperature or rainfall, or a change in the usual wind directions
Climate change is constant over what scales of time
Long, medium and short scales of time
It has and always will be
Explain long term climate change
Taking temperature as an indicator of climate, there have been huge changes over earths history-temperature has been much higher at some points in the past than they are today
Over the last 400,000 years there has been greatest fluctuation
Climate shifted between cold glacial periods that lasted around 100,000 and warm interglacial periods that lasted around 10,000 years-currently in an interglacial period
Explain medium term climate change
The last glacial period ended around 18,000 years ago
The warming of the climate after this was fast at times, but it was not constant-about 13,000 years ago the climate switched back to cooler conditions for about 1,000 years
Around 5,000 years ago, temperatures were 1-2degrees warmer than today
Explain short term climate change
Global warming is the term used for the rapidly increasing global temperature over the last century-there’s been a sharp rise in temperature when you look at the last 1,000 years
Overall pattern over the last century shows a general increase in temperature, but the pattern has no been constant
Global temperatures rose steadily from the early 20th century until the 1949’s (although they fluctuated annually), then dropped back down-scientists thought there would be another glacial period,but temperatures have rise rapidly again since the 1970’s (this is global warming)
3 evidences that support long term change
Ice cores
Pollen analysis
Sea level change
Explain ice cores (long)
Scientists drill deep into ice sheets (huge masses of ice) to extract ice cores. Ice sheets are made up of layers of ice p-one layer is formed every year. So the ice at the bottom of the core is really, really old
They can analyse the gases trapped when the ice formed to tell what the temperature was each year. Then they can figure out how temperature has changed over time
Eg. a core has been extracted from an Antarctic ice sheet to a depth of 3,000m and has been used to show temperature for the last 400,000 years
Explain pollen analysis (long)
Pollen taken from plants is often preserved in sediment
The preserved pollen can be identified and dared to show when it was released
Scientists know the conditions that plants live in now. When they find preserved pollen from similar plants, it indicates the conditions were similar when that pollen was pollinated
Explain sea level change (long)
Sea level is affected by things like the volume of water stored as ice
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 (ie. it was warmer)
3 evidences that support medium term change
Historical records
Tree rings
Retreating glaciers
Explain historical records (medium)
Historical records can indirectly indicate different conditions in the past, eg agricultural reports (such as harvest times) show changing conditions throughout human history
Explain tree rings (medium)
A new ring is formed each year as a tree grows
Of conditions that year were good, the tree ring produced will be thick
Scientists can take cores and count the rings to find the age of the tree, then they look at the thickness of each ring to see what the climate was like each year
Tree rings can reliably show and date climate conditions up to 100,000 years ago
Explain retreating glaciers (medium)
Scientists can tell hoe big a glacier was and how far it extended by looking at the position of rocks deposited by it-these rocks can be dated to show when they were deposited
The distance of the rocks from the current glaciers in dictates climate change, eg if the front of the glaciers is now miles away from the rock it indicates that temperatures have increased over that period of time
3 evidences that support short term change
Weather records
Polar ice melt
Ecosystem changes
