In the following passage, some words have been deleted. Read the passage carefully and select the most appropriate option to fill in each blank.

Changes to the earth's climate, driven by increased (1)______ of heat-trapping greenhouse gases, are already having widespread effects on the environment. Shrinking of glaciers and ice sheets, occurrence of shifts in flower/plant blooming times, etc., are creating an overall (2)________ in the natural ecosystem. Conditions like the rise in sea-levels and saltwater intrusion have advanced to the point where whole (3)__________ have had to relocate, while protracted droughts are putting people at risk of (4)________. The effects of human-caused global warming are (5)_______ for people alive today and will worsen as long as humans keep feeding greenhouse gases into the atmosphere.