This is not a possible adverse effect of global warming

The correct option is "an increase of UVB radiation".

To understand why this is the correct answer, let us analyze the relationship between global warming and each of the options provided:

1. Sea level rise: Global warming causes global temperatures to rise. This leads to the thermal expansion of seawater and the melting of land-based ice sheets and glaciers, both of which directly contribute to sea level rise. Therefore, this is a possible adverse effect.

2. Retreat of glaciers: Higher atmospheric and ocean temperatures accelerate the melting of glaciers worldwide. The retreat of glaciers is a well-documented consequence of global warming. Therefore, this is a possible adverse effect.

3. Extraordinary weather patterns: Increased thermal energy trapped in the atmosphere alters global climate systems, leading to extreme and extraordinary weather events such as severe droughts, intense heatwaves, heavy rainfall, and stronger storms. Therefore, this is a possible adverse effect.

4. An increase of UVB radiation: Ultraviolet-B (UVB) radiation reaches the Earth's surface primarily due to the depletion of the stratospheric ozone layer, which is caused by ozone-depleting substances (ODSs) like chlorofluorocarbons (CFCs). Global warming itself is driven by greenhouse gases (such as carbon dioxide and methane) trapping infrared radiation in the lower atmosphere. An increase in UVB radiation is not a direct result or a possible adverse effect of global warming.

Hence, an increase of UVB radiation is not a possible adverse effect of global warming.