In the context of climate change, which of the following observations are correct for the 20th century with reference to 1750?

1.The global average surface temperature has increased by 0.6 degrees Celsius

2.A greater increase in daytime temperature than night-time has been observed

3.The global average sea level rose by 0.1 to 0.2 m, largely due to thermal expansion

4.The atmospheric concentration of carbon dioxide has increased by 31 percent

5.Precipitation in the northern hemisphere has decreased by 1 percent per decade

A1, 2, 4 & 5 only

B1, 3 & 4 only ✓ Correct

C2, 3 & 4 only

D1, 2, 3 & 4 only

Correct answer: (B) 1, 3 & 4 only

Explanation

Statement 1, Statement 3 and Statement 4 match the recorded 20th century observations.

Statement 1 is right, as global average surface temperature rose about 0.6 degrees Celsius.

Statement 2 is wrong, because night time temperatures rose more than day time ones.

Statement 3 is right, as sea level rose 0.1 to 0.2 metres, largely from thermal expansion.

Statement 4 is right, since atmospheric carbon dioxide increased by about 31 percent since 1750.

Statement 5 is wrong, because precipitation in the northern hemisphere increased, not decreased.

These figures come from the IPCC Third Assessment Report of 2001.

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