An introduction to climate change

Section 1: What is climate change? Recent climate history and future projections

Weather is the state of the atmosphere, to the degree that it is hot or cold, wet or dry, calm or stormy, clear or cloudy. Most weather phenomena occur in the troposphere, just below the stratosphere.

What is weather?
At every moment at any spot of the world, the troposphere (the inner layer of atmosphere which contains earth’s most of the air) has a particular set of physical properties – i. Temperature, ii. air-pressure, iii. humidity, iv. precipitation, v. sun-shine, vi. wind direction and speed. These short term properties of atmosphere at a particular place and time are weather.

What is Climate?
Climate is a region’s general pattern of atmospheric or weather conditions over a long period. Average temperature and average precipitation are two main factors determining a region’s climate.

What is climate?
• The long-term average of a region’s weather:
– Average rainfall. – Average hours of sunshine. – Average temperature.

• Climate versus weather:
– Weather describes whatever is happening outdoors in a given place at a given time. – Climate describes the total of all weather occurring over a period of years in a given place. – Climate tells us what it's usually like in the place where you live at a certain time of year.

Climate change
• Climate change represents a change in these long-term weather patterns.
– Average temperatures can increase or decrease. – Rainfall can increase or decrease, as can hours of sunshine.

• Climate change has occurred naturally over millions and millions of years. • However when scientists talk about the issue of climate change, their concern is mostly about global warming caused by human activities.

 Climate change is caused by factors such as biotic processes, variations in solar radiation received by