All of the options listed are effects of global warming, but the fourth option, "changing seasons every year," is not a direct result of global warming. Global warming primarily refers to the long-term increase in average global temperatures, which leads to various impacts such as rising sea levels, increasing greenhouse gas concentrations, and higher levels of carbon dioxide in the atmosphere. Changing seasons can be influenced by other factors, such as natural climate variability, but it is not directly caused by global warming.
The effect of global warming is increasing carbon dioxide in the atmosphere.
The correct answer is "rising sea level over a period of time." Global warming causes the Earth's temperature to increase, which in turn causes ice to melt. This melting ice leads to the rising of sea levels, as the melted ice water flows into the oceans. To determine this, one can consult scientific literature, reports from climate organizations, or reliable websites that provide information on climate change and its effects.
