Read the following paragraph and answer the question that follows:

Global surface temperatures in 2019 are on track to be either the second or third warmest since records began in the mid-1800s, behind only 2016 and possibly 2017. On top of the long-term warming trend, temperatures in 2019 have been buoyed by a moderate El Niño event that is likely to persist through the rest of the year.

Which of the following statements can be BEST inferred based on the above paragraph?

From the passage, we can understand that El Niño is an event that has affected the global surface temperatures only in 2019 and that it is likely to persist through the rest of the year. So it is unlikely that it will have any long term effects.
There is no comparison of moderate and weak El Niño in the passage.
There is no mention about El Niño occurrence in 2016 and 2017, therefore, it would be incorrect to assume anything. 
From the data given it is clear that in 2019 the temperature, though high, is less than that of 2016 and 2017 so it is not true that global surface temperatures are increasing at a constant rate for the last three years.
Hence the correct option is D.