Past Climate

Extinction: the changing face of the biosphere

In the Earth’s 4.6 billion year history, over 99% of all the species that have ever existed have become extinct. In the majority of cases, these extinctions are due to competition between species for space, food, or other resources; or that a species did not adapt sufficiently or quickly enough to changes in the environment. Extinction is a natural and on-going part of the biosphere’s engineering that continues at a background rate. This constant cycle of extinction, adaptation, and evolution means that as one species meets its demise, another will take its ecological niche. Over long time periods (thousands or millions of years), this can...

Alpine plants and recent climate change

Alpine plants grow above the altitudinal tree-line in mountains around the world. Because alpine plants grow in areas with low summer and winter temperatures, very low night temperatures, frost, short growing-season, high winds, or extended snow-lie, and grow very slowly, it is widely accepted that alpines grow in such extreme habitats because of their physiological tolerance or requirement for cold conditions and/or their intolerance to competition from taller, more rapidly growing lowland or montane plants. Some, but certainly not all, alpines can, with care, be successfully grown in lowland gardens in the absence of competition from tall plants. Alpine plants are thus potentially sensitive to climate...

Climate history from lakes

Lakes are distributed widely across the globe, and depending on their location, they can be particularly sensitive to changing climate.  For example, global warming is having a significant impact on lakes in polar and alpine environments, while variation in rainfall patterns impacts on lakes in semi-arid regions.  In order to understand the climate history that can be obtained from lakes, we need to briefly consider how temperature and precipitation affect different types of lakes.   In cold, polar-regions, lakes are normally covered by ice for many months of the year.  During spring, the ice melts and winds help mix the water up, which also ensures...

Challenged by carbon: rocks and climate change

You can’t argue with a rock.  So ideally we would now be on a field trip.  Instead, I offer you a short film made in the field by the Science Museum to accompany a lump of Hertfordshire Puddingstone that is featured in the Atmosphere Gallery, first opened in 2010.   Thanks to geology, the scientific case for human-induced climate change has recently become significantly more plausible.  New observational science based on cores taken from deep beneath the floor of the oceans offers crucial support and control for the computer-based forecasts of those creating models of future climate change.  Thanks to the work of the late...

Cave deposits (speleothems) as archives of environmental change

Speleothems, from the Greek words for cave and deposit, include the familiar descending stalactites, upward-growing stalagmites and more continuous sheets called flowstones.  They grow slowly, at rates of between 1 mm a year to 0.001 mm a year.   This growth can persist for many thousands of years before being interrupted.  As with trees, speleothems commonly display annual layers which may be visible when a sample is polished, or recognised through chemical analyses.  Ideally, a sample will accumulate regular, parallel layers,  allowing the investigator to study its growth through time, and see changes in environmental conditions. These speleothems grow in caves within limestone rock.  Typically the...