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By Daniel Collins

On average, about 87% of the Earth’s evaporation takes place over the oceans. 9% of this water then makes it over the land and falls as precipitation, the rest falls back to the sea. But this is just an average. Over much of 2010, there was so much evaporation from the oceans that the global average sea level actually dropped 6 mm.


With more water circulating in the atmosphere, some parts of the planet received much heavier rainfalls, triggering the floods in Australia, Pakistan and Venezuela. This extra water can be detected by its effect on the gravitational pull around the Earth, as measured by GRACE (Gravity Recovery and Climate Experiment). (GRACE figure courtesy of NASA/JPL-Caltech.)


These changes were associated with a dramatic shift from El Nino to La Nina conditions. For New Zealand, La Nina conditions tend to bring more rain to the north-east of the North Island and less to the south and south-west of the South Island, but we’ll talk about this more in the future.

Of course, as the extra water on the land eventually flows to the sea, we can expect a similarly abrupt rise in sea level, on top of the trend associated with global warming.

(H/T: Hot Topic)