Past Climate

Mangroves and mud: Investigating past sea level

Dawn had already broken when our plane touched down on Mahé island, lighting up the cloudy shifting sky and the turquoise waters lapping at the runway’s edge. From my plane window I could already see sheer cliffs of pinky-grey granite rising up from the narrow coastal plain, covered in lush tropical vegetation. I was sleepy, but excited to be here. Mahé is the largest island of the small island nation of Seychelles – a tropical archipelago in the western Indian Ocean. I was visiting for three weeks to begin the field work component of my PhD research. My destination: the mangroves that fringe the western...

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...