Climate Variability and Weather
In progress from 01-10-2011 to 01-01-2012
Project manager: Dr Jonathan Wentworth
The Earth's climate is dynamic and naturally varies on all time scales, from one year to the next, as well as from one decade, century or millennium to the next as well as on all spatial scales, from the regional to the global. Each "up and down" fluctuation can lead to conditions which are warmer or colder, wetter or drier, more stormy or quiescent. There are two types of natural climate variability. The first arises from natural external influences on climate, such as changes in the energy from the sun reaching the Earth’s atmosphere. The second type of long-term natural variability is due to internal processes in the climate system, for example, north-south shifts of the atmospheric eddy-driven jet stream steers weather systems across the North Atlantic, determining the storm climate and influencing precipitation and temperature across large areas of Europe. Another example is the El Nino-Southern Oscillation (ENSO), a combined ocean-atmospheric interaction driven by changes in upper ocean temperatures in the tropical Pacific Ocean, which affects weather patterns worldwide, including monsoon rains in South Asia.
While global average temperatures are expected to increase over coming decades due to greenhouse gas emissions, year to year variation in weather patterns will be dominated by the behaviour of such climate phenomena. This POSTnote will consider the major internal processes affecting climate variability, whether the behaviour of these phenomena can be predicted with any accuracy and the likely impacts of climate change on their behaviour.