Past Climate

Oxygen Isotopes in Speleothems

Stalactites and stalagmites (also called speleothems) are found in cave environments across the planet (see Figure 1). They form as water from the surface percolates into the ground and drips into the cave. Speleothems can be extremely sensitive to changes in climate and environmental conditions and they record these changes as variations in their chemistry. An excellent review of speleothem formation and their use for palaeoclimate reconstruction by Prof. Ian Fairchild can be found here, so this article focuses on the way that oxygen is stored in speleothems and how we can use this as a record of past climate conditions.   Why and how do we use oxygen isotopes? Oxygen...

Key Facts for Future Climate – COP21

COP21 – Paris Climate Conference 30th November to 11th December 2015 Key facts for future climate    What is COP21? And who is involved? COP21 has involved two weeks of talks between government officials from around the world. The goals are: To agree legally-binding, global targets on cutting carbon emissions to keep global warming below 2°C. To therefore reduce the impacts of man-made global warming beyond 2020. To discuss ways of helping developing nations to continue their development in a sustainable way. There have been over 50,000 participants from governments, the United Nations (UN), and Non-Governmental Organisations (NGOs). 195 countries were represented, and world leaders were present for...

Snail shells provide detailed records of environmental change

By Dr Jonathan Lewis and Prof Melanie Leng The shells of molluscs from all over the world – on land, in lakes, and in the ocean – contain very detailed imprints of past climate change. Using isotope analysis, we can extract these signals and start to piece together long-term climate variations. You will never look at a garden snail in the same way again! What are molluscs? Molluscs are soft-bodied (invertebrate) organisms that are widespread in terrestrial, freshwater, and marine habitats. We can split them into two basic groups: Gastropods: Molluscs with up to one shell or ‘valve’ (such as snails or slugs) Bivalves: Molluscs...

Understanding past sea-level change

Sea-level change is an important consequence of climate change, whether natural or anthropogenic.  Global mean sea level has been rising. For the 20th century, the average rate was 1.7 ± 0.5 mm yr–1 (IPCC AR5), and in some locations (such as the east coast of the USA) there is some evidence that the rate of sea-level change appears to have increased from the 19th to 20th centuries.  However, sea-level change is not a global process but in fact the sea level at any location and at any time is result of a complex combination of a range of factors.  Changes in sea level are a result of any...

Can isotopes help define the Anthropocene?

By Dr Jonathan Dean, Prof Melanie Leng and Prof Anson Mackay   The Anthropocene is a term that is increasingly being used to refer to the current interval in geological time in which humans have become a dominant force of global environmental change. It was coined by Prof Eugene Stoermer, a biologist, in the 1980s and popularised in the early 2000s by Prof Paul Crutzen, an atmospheric chemist. It is now indisputable that humans are leaving their mark on the planet (see the recent Climatica summary of the ‘Climate change: evidence and causes’ report here: http://climatica.org.uk/royal-society-national-academy-sciences-climate-change-evidence-causes). For instance, over the last century or so, atmospheric...