Physical and human causes

There is evidence to show that our climate is changing. This is due to a combination of physical and human factors. Climate change can have a range of impacts in different areas. The map below shows areas presently at risk from climate change.

Water stress and drought

How our climate has changed

Our climate is continually changing. A variety of sources provide evidence of climate change over different periods of time:

Ice cores - locked inside ice are molecules and trapped air, which are preserved year on year as more snow falls. Subtle changes in temperature can be measured from ice cores extracted in Antarctica. This gives scientists long term evidence of climate change.

Rocks and fossils - these can be studied for information also covering longer time periods. For instance, limestone found in Yorkshire would have been formed on the bottom of a warm seabed millions of years ago.

The video below describes global warming and polar ice cap evidence.

Ice cover - areas such as Greenland and the Arctic have seen thinning of ice sheets. Overall the 2014 Arctic Sea ice maximum was the fifth lowest in the 1978 to 2014 records, with the amount of winter ice cover falling to its fifth lowest on satellite record, according to scientists at the US National Snow and Ice Data Centre. Arctic Sea ice extent for March averaged 14.80 m sq km. This is 730,000 sq km below the 1981-2010 satellite average.

The latest findings reinforce a trend that could see the Arctic losing all of its ice cover in the summer months within decades.

Glacial Lakes from Retreating Glaciers
Glacial lakes from retreating glaciers

Glacial retreat - photographs, satellite images and staking the changing position of the terminus, or snout, at the end of a glacier show that many mountain glaciers have retreated in the last 50 years. However, this could partly be due to a lack of snowfall as well as glacial melting.

Pollen analysis - Different types of plant are adapted better to different conditions. Study of plant pollen preserved in sediment can show changes in the type of vegetation in a particular area. This provides a guide to what the climate was like at different times.

There is also recent evidence such as changes in biodiversity, climate records and sea ice limits.

Since around 1950, there is evidence of a steep climb in global temperatures compared to the past. This trend is called global warming.

The video below discusses the evidence for global warming, specifically sea level change.