Attention has begun to shift from local, short-term seasonal patterns of temperature, rainfall, other elements of the weather, toward longer-term trends that can affect the entire Earth, se long-term (typically 30-year) weather trends are called "climate." It is therefore important understand the difference, as well as the relation, between "weather" and "climate."
An example of the relationship between weather and climate is El Nino, which is weather with local, short-term consequences as well as with global, long-term importance. In the ort-term. El Nino can bring a dry summer for some regions and a wet winter for others; however, over the course of many years, the number of times El ...view middle of the document...
Global climate has been changing and still continue to change. Over a long period of time, climatic fluctuations may be such that, a shift in type of climate prevailing over a given area, takes place. In that case, we talk of a change in climate or climatic change. Various terms used to describe variations in climate, namely, climate variability.
Climatic fluctuations, climatic trends, climatic cycles and climatic change, refer to some appropriate time scales and can only be validly used within such time scales. The evidence of past climatic change is many and varied, such biological, lithogenic and morphological.
Prior to the 1990s, scientists largely believed that the shifts in climate between ice ages and warmer periods occurred over centuries and millennia due to the large amount of time
necessary to build up or melt an ice sheet over a kilometer in thickness. Geologic evidence from the last decades, however, shows that there have also been rather abrupt periods of climate change spanning anywhere from years to decades.
Abrupt climate changes can occur when variable that change gradually push the Earth's system across some limit of instability. One of the known examples of this rapid change is the Younger Drays, which was a sudden interruption gradual global warming that began 12,800 years ago after the end of the last glaciations.
The sudden return to a cold global climate lasted for 1,200 years and was followed by a very rapid warming of about 8°C over the course of 10 years.
Climate' variation occurs as a response to "climate forcing," which are factors that cause either a warming or cooling of the atmosphere. Over most of the Earth's history forcing have been entirely natural, caused by continental drift, variability in solar radiation, chain in the Earth's orbit, and volcanic emissions.
However, since the industrial revolution, human activity has had a large impact on the global climate system, increasing the amount of greenhouse gases in the atmosphere, trapping heat and contributing to global warming.
The Intergovernmental Panel on Climate Change (IPCC) reported that the Earth's average surface temperature during the 20th century increased approximately 0.6°C. While this may seem like a small change, global temperatures are generally quite stable. The difference between today global temperature and the average global temperature of the last ice age is only about 5t.
However, over the last century we have witnessed a decrease of nearly 10 percentage snow cover and a 10-15 percentage decrease in spring and summer sea-ice in the northern hemisphere] Other observed changes that have been linked to climate include longer growing seasons, increases in rainfall and rainfall intensity in the northern hemisphere, and shifts in when ice freezes and breaks up on rivers and...