Also known as global warming, it refers to the rise in average surface temperatures on Earth. This is mainly cause of fossil fuels which release carbon dioxide and other green house gasses into the air.
Climate change is the change in average weather or climate over a long period. The change manifests itself most clearly in an increase or decrease in the average temperature, changes in the prevailing wind direction and in the water cycle and thus in the cloud cover and the amount of precipitation on earth. These changes have an impact on desertification, wetlands, flooding by rivers that flow beyond their banks and the size of ice caps and glaciers. In the longer term, climate changes also affect sea currents, sea level and the salinity of seawater.
Climate change came to the fore at the end of the 20th century due to observed global warming. In the geological past there have been periods when it was most hot and humid on land or very hot and dry. There have also been times when it was much colder on earth than it is now, such as during the ice ages. The differences in climate during the different periods are greatest in the polar regions and around latitudes where there is a moderate climate in modern times. They are the smallest around the equator and between the tropics.
The Europeans brought many diseases with them that decimated Native American populations. Colonists and Native Americans alike looked to new plants as possible medicinal resources.
