National Climate Change Information System
Weather describes the current conditions of the air around the earth and is constantly changing - is it sunny, rainy or windy? That is the weather! Weather can be seen and felt and it changes constantly and differs for different places.
Climate looks at the average weather conditions recorded and studied over a long period of time (30 years and more) for a place and groups it accordingly, i.e South Africa is a semi-arid region (this means that the country is generally dry and receives rainfall peaks primarily during the summer season). Climate change is already a measurable reality and along with other developing countries, South Africa is especially vulnerable to its impacts.
What is climate change?
The phenomenon known as “climate change”, refers to an ongoing trend of changes in the earth’s general weather conditions as a result of an average rise in the temperature of the earth’s surface often referred to as global warming. This rise in the average global temperature is due, primarily, to the increased concentration of gases known as greenhouse gases (GHGs) in the atmosphere that are emitted by human activities. These gases intensify a natural phenomenon called the “greenhouse effect” by forming an insulating layer in the atmosphere that reduces the amount of the sun’s heat that radiates back into space and therefore has the effect of making the earth warmer.
While weather changes on a daily basis, climate represents the statistical distribution of weather patterns over time, and on a global scale has changed only very slowly in the past – usually over periods of tens of thousands of years or even millions of years which allows time for the earth’s bio-physical systems to adapt naturally to the changing climatic conditions. Currently, the global climate is changing much more rapidly as a result of global warming, leading to, among others, the melting of polar and glacier ice, sea-level rise, ocean acidification, changes in rainfall and snowfall patterns, more frequent floods and droughts and increased frequency and intensity of extreme weather events, such as tornadoes, hurricanes and cyclones. The rapid rate of this climate change does not allow the earth’s bio-physical systems to adapt to these changes naturally.
Evidence of rapid climate change, including more frequent and intense weather systems and greater climate variability, has already been observed and includes:
increases in the average global temperature; with the past decade being the hottest on record;
rises in the average global sea level;
changes in average rainfall patterns, with some regions experiencing higher rainfall (e.g. Northern Europe) and other areas experiencing drying (e.g. the Sahel and southern Africa);
increased frequency of heavy rainfall and extreme weather events over most land areas; and
more intense and longer droughts, particularly in the tropics and subtropics.
What causes climate change?
Greenhouse gases (GHGs) are emitted from, and are reabsorbed by, a variety of natural sources, but the rate at which human economies and societies are emitting these gases far exceeds the capacity of natural ecosystems to reabsorb them. Increased industrial activity since the mid-18th century has led to a rapid increase in the atmospheric concentration of GHGs such as carbon dioxide, methane and nitrous oxide, in large part due to the burning of fossil fuels derived from oil, coal and natural gas.
The rate of emissions has been steadily increasing over time, and computer models of the earth's climate system (including both natural and human causes) are unable to simulate recent warming unless they include anthropogenic emissions of greenhouse gases.
Land-based human activities, such as forest clearing and unsustainable agricultural practices, are not only increasing GHG emissions from these sources, but are also reducing the earth’s natural ability to absorb GHGs. The evidence that current global warming is due to human activities associated with industrialisation and modern agriculture is overwhelming.