How has climate changed since the beginning of the Quaternary period?

Climate change is any significant change in the Earth’s climate over a long period. Global temperatures have fluctuated (gone up and down) throughout the Earth’s history.

The Earth is estimated to be 4.55 billion years old, and its history has been divided into eras, periods and epochs through a geological timescale.

The current period, called the Quaternary period, spans from 2.6 million years ago to the present and is part of the Cenozoic era. The Quaternary period marks a cooling trend, starting the most recent ice age (out of five believed to have occurred). It is divided into two epochs: the Pleistocene and the Holocene.

The Earth’s climate was warmer and more stable before the Quaternary. Since then, things have changed quite significantly.

Global temperatures have shifted between cold glacial periods and warmer interglacial periods. As you can see from the graph below, glacial periods have lasted around ten times longer than interglacial periods.

Since the last glacial period, 15000 years ago, the climate has been warming. Global warming is the term used to describe the rapid increase in global temperatures over the last century.

What is the Evidence for Climate Change?

Global climate change occurs very slowly over thousands of years. Since 1914, the Met Office has recorded reliable climate change data using weather stations, satellites, weather balloons, radar and ocean buoys. The Earth’s average surface temperature has increased by approximately 1 °C over the last 100 years. Additionally:

• since 1900 sea levels have risen by 19 centimetres and are expected to rise due to thermal expansion and melting ice sheets.
• Ocean temperatures are the warmest since 1850, and glaciers are retreating.

Scientists have used a range of evidence to work out changes in the Earth’s climate.

Ice and Sediment Cores

An ice core is a sample taken from a glacier or ice sheet. It involves drilling down into the ice and removing a cylinder of ice. As ice is formed in layers, it is possible to analyse gasses from each year. From this, scientists can work out the temperature at the time. Ice cores can be taken from Antarctica, which provides information for the last 400 000 years. Samples of sediment taken from the ocean floor can also indicate temperature over time. It has been possible to gather data from the last 5 million years by using this technique.

Temperature Records

Thermometers have been used to measure temperature since the 1850s accurately. This provides reliable, short-term data on climate change.

Tree Rings

Each year a tree grows, it forms a new ring. The width of the ring indicates the climatic conditions for the year. The thicker the ring, the warmer and wetter the climate for that year. Tree rings help give an indication of climatic conditions over time.

Pollen Analysis

Analysing pollen preserved in peat bogs or the bottom of lakes indicates the species living in the past. This indicates temperatures based on what we know about the conditions different plants thrive in.