Which of the following statements about secondary succession is true? a.
Secondary succession occurs in ecosystems that have no vegetation.
b.
Secondary succession affects ecosystems that are already established.
c.
Ecosystems require pioneer species to undergo secondary succession.
d.
Secondary succession can occur in areas without soil.

it is very hard for the climatologists to precisely predict how will the global temperatures be changing so there's lots of models, some of which differ significantly, this is due to multiple factors, and probably the most important is the human activity.

humans have been a key factor in climate change around the globe since the start of the industrial revolution, and in the past few decades the consequences are becoming more obvious. there's lots of emission of pollutants in the atmosphere as well as changing the environment on the surface itself, so it's really hard to predict how will that go in the future because there's some countries that are reducing the damage and are going towards green energy, while others are stubbornly continuing with pollution and damages to the environment.