How and why have debates over american national identity changed over time?

What something thats on the news, and is going on currently?

What do most climatologists see as a major cause of rising global temperatures? a. earth's closer proximity to the sun due to its gravitational pull b. greenhouse gases produced by burning fossil fuels c. rising ocean levels caused by melting polar ice sheets d. water pollution cause by industrial waste

Which events are correlated but do not necessarily have a causal relationship?