During the twentieth century, earth’s average surface temperature

The earth's average surface temperature increased.

The global average surface temperature has increased over the 20th century by about 0,6 degrees Celsius.

The increase has been stable since 1861. The 1990's were the warmest decade and the 1998 the warmest year in the instrumental record, since 1861.

The temperature has risen during the past four decades in the lowest 8 kilometers of the atmosphere.

Global average sea level has risen and ocean heat content has increased as well.

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