Evidence for climate change

Observations

• Historical records: such as agricultural reports can show us that there was different conditions in the past
• Weather records: These have been collected since 1861 and can be used to show detailed climate changes over the short period that they have been collected

Physical

• Ice cores: Analysing the gases trapped in the ice cores that scientists drill out of ice sheets they can tell what the temperature was each year, and how it's changed 
• Sea floor sediments: Sediments that are deposited on the see floor can be tested for the chemical composition of the sea water when they were deposited, which again can indicate the temperature of the time period
• Sea level change: Sea level is affected by the volume of water stored as ice. Some valleys formed above sea level are now submerged showing that sea level is rising for example (Poole harbour in Dorset)
• Retreating glaciers: Looking at historical photos scientists can tell where these glaciers were originally and the distance they are now from them indicates climate change

Biological 

• Pollen: Pollen is preserved in sediments, upon analysis scientists can see what plant it came from and therefore the climatic conditions that it needed to live in, this allows them to compare it to what climate pollen is produced in now
• Tree rings: A tree grows a new ring each year, the thickness of the rings indicate the climatic conditions they were in. By taking a core of a tree scientists can see how the climatic conditions have changed each year.