Which one of the following is not a cause for the present global warming and climate change ?

Global warming and climate change are primarily driven by the accumulation of greenhouse gases (GHGs) that trap heat in the atmosphere. Carbon dioxide (CO2), methane (CH4), and nitrous oxide are the most significant contributors [3]. Deforestation is a major cause because trees release stored carbon when cut and their removal reduces the Earth's capacity to absorb CO2 [t1][t2]. While Chlorofluorocarbons (CFCs) are potent greenhouse gases that contribute to global warming [c2][c3], they are primarily recognized for their role in stratospheric ozone depletion. In the context of this specific question (often appearing in older UPSC papers), CFCs were historically distinguished from the 'main' drivers of the 'present' greenhouse effect compared to CO2, methane, and land-use changes like deforestation. However, scientifically, all four options contribute to warming; within the standard examination logic, CFCs are often the 'odd one out' due to their primary association with the ozone hole.

Sources

1. [1] Environment, Shankar IAS Acedemy .(ed 10th) > Chapter 29: Environment Issues and Health Effects > Greenhouse gases (GHGS) > p. 426
2. [3] Environment and Ecology, Majid Hussain (Access publishing 3rd ed.) > Chapter 7: Climate Change > 2. greenhouse gases > p. 9