Joseph Fourier pinpointed the Greenhouse Effect in 1824, but it wasn't first quantitatively investigated until 1896, when Svante Arrhenius carried out his studies.

The Greenhouse Effect, the way in which "absorption and emission of infrared radiation by atmospheric gases warms a planet's atmosphere and surface", is a natural occurrence which we are actually reliant on. Whilst we hear the term spoken of with negative connotations, if it wasn't for this warming effect the Earth's temperature would be an estimated 30°C cooler, making the planet uninhabitable. Therefore, any debate around this topic is not disputing the existence of the Greenhouse Effect, rather the full length of its implications and our influence over it.

The predominant greenhouse gases in the Earth's atmosphere are water vapor (36-70% of the Greenhouse effect), carbon dioxide (CO2) (9-26%), methane (CH4) (4-9%), and lastly ozone (3-7%).

The amount of carbon dioxide has increased by 31%, and Methane by 149% since 1750 - higher than at any time in over half a million years. This has been deduced by studies on ice cores.

References: www.wikipedia.org