Glaciers advance when temperatures are cool and retreat when temperatures are warm. Glaciers leave behind moraines, unconsolidated glacial debris, which contain organic data which can be accurately dated. From 1940s to 1970s evidence shows that glaciers were retreating i.e. warm temperatures. From the 1970s to 1980s there had been stable growth i.e. cool temperatures. And from the 1980s to present there has evidence that glaciers have been retreating i.e. our planet is warming.
Air from Greenland and Arctic ice sheets can be sampled from bubbles trapped in the ice as it was laid down over thousands of years ago. Carbon dioxide level from the former atmosphere can be reconstructed. This evidence shows that in the past carbon dioxide emissions have been very low, as low as 180ppm. When this evidence is put against rise in temperatures global warming seems to be happening!
Dendrochronology (Tree rings)
Dendrochronology examines trees and their growth. For example, a thick and fat tree ring means the soil and conditions were fertile hence good rainfall. Whereas, narrow trees indicate poor and low rainfall conditions. So just as with vegetation we can work out the climate of a period of a time as climate affects rainfall. Evidence shows that in the last 50 years ago that temperatures have been 1.5-2 degrees higher than the median and higher than ever before in 7000 years.
Palynology allows scientist to examine climate change through pollen analysis. From this we can infer past climates – up to thousands of years. Evidence from this kind of data shows a steep rise in temperature from1900s to present of about 1degree.
Paintings, poems and diaries
These evidence show that there was a mini ice age between 1000-1850. Then from 1850 to present we can just see evidence for warm conditions.
Records of dates from French grape harvests have usually been used to identify warm and cold periods. From the reconstruction of this data we have seen several warm summers like those of 1900s. However, Summer 2003 heatwave was by far the warmest of them all. Is this evidence for climate change?
The ice sheets of Greenland, the Canadian Arctic and Antarctica are aerially monitored continually. As we are all aware that evidence shows that these ice sheets are melting quicker than anticipated. This is claimed to have something to do with increased temperatures caused by climate change.
Analysis of vegetation through a time period gives evidence for climate change. This is because a change in climate affects precipitation and how well plants cope.We are witnessing extreme examples of this e.g. desertification in Africa.
1. What is Palynology?
2. What does evidence from polar ice caps show?
3. What is dendrochronology?
4. What does evidence from Glaciers show?
5. How does ice cores provide evidence for global warming? What is the evidence?
1. Palynology is the study of pollen to work out climates of different periods in history.
2. Evidence from polar ice caps shows that ice sheets are melting quicker than we anticipated.
3. Dendrochronology is the study of tree rings to work out climates of the past.
4. Evidence from glaciers shows that from the 1980s to presents glaciers have been retreating i.e. climate is getting warmer.
5. Ice core allow us to measure the amount of carbon dioxide that has been in the atmosphere is the past. This shows that in the past co2 emissions have been so little some as low as 180ppm. This shows a positive correlation with temperature increases.