The conclusion is that "rising number of disasters adversely affecting people". It would make more sense if it was stated this way:
"Earthquakes, volcanic eruptions, and unusual weather have caused many more natural disasters which have adversely affected people during the past decade than in previous decades."

The conclusion is weakened because it is not that the earth has become more dangerous due to disasters that affect people occurring more often. It is that the earth has taken on an appearance of being more dangerous, due to people moving into more dangerous areas.

(A) The weather and earth sciences have provided better early warning systems for natural disasters in the past decade than in previous decades.

The alarm system for tsunami or else is out of scope. We want to know if the earth is dangerous more than in the past, OR if it is so because of climate change or else.

Think this way also: since ever when rains a lot the rivers grow in volume due to the rain BUT they need a natural decompression zone outside their bed where they naturally flood. However, the growing density of population force the gov to rise building or housing NEAR the rivers or byside them. When a flash flood occur we do have a disaster. BUT is not the river than causes this , is the construction amassed in those areas where we should not.

Regards