What we call global warming is a particular case of climate change. Particular and very important, as it underlies possible changes that will be felt within this century and affect our sons and daughters. It is also particualr because it is the first example of climate change brough on by large scale human activity.
Climate change can have many causes more in general, and over most of the planet''s life they have been natural ones (we were not even around). Changes in geomorphology, including distribution of oiceans and continents; changes in vulcanic activity; solar irradiance; etc. etc.
The greenhouse effect is a natural fenomenon, as it refers to the additional capture of heat in the atmosphere by so called trace gases, tehe key being water vapor, CO2 CH4 and N2O. It underlies a good part of the mechanisms through which climate change happensa
Any natural cycle that is capable of altering these trace gases also results, potentially, in climate change. Conversely, small external changes can also be magnified by their indirect effects on atmospheric gases.
It is for instance the case of anthopogenic CO2. The global warming effect brought on by the increase in this gas from human activities are magnified by a number of feedback, the two largest being the water-vapor feedback (more co2, more heat, more evaporation, more water vapour in the atmosphere, more greenhouse trapping, more heat...) and the water vapour-cloud feedback (...more water vapour, more condenstation, more clouds ...more or less radiation at the surface, dpending on clouds height).
Finally, it is not the first time that life has changed the climate. Think about the faboulous revolution brought on by photosynthesis, which led to significant decreases in atmopsheric CO2 and significant parallel increases in oxygen (and ozone in the stratosphere). A significant functioning biosphere and its effects on the carbon cycle provide important feedback that play a role in climate, including glacial interglacial cycles.
Explanation:
