Ocean temps hint at warming trend

Climate scientists at the Jackson School of Geosciences address common myths about climate change in this eight part series.

Myth No. 7: Natural ocean variability can explain the observed warming.

Ginny Catania
Ginny Catania

The oceans are the largest single reservoir of heat in the climate system. And they do have internal cycles of variability, such as the Pacific Decadal Oscillation (PDO) and the Atlantic Multi-decadal Oscillation (AMO). These cycles have impacts on the sea surface temperature in specific regions that vary from year to year and even from decade to decade. So perhaps, the argument goes, we just happen to be in a warm period that will last a few decades and the oceans will eventually switch back to a cool period.

Rong Fu, an expert in climate observations, said the top 100 meters of the oceans are experiencing an upward trend in temperature all across the planet. She said that cannot be explained by any known ocean cycles.

The AMO is in a warm phase, but the last time that happened, in the mid 20th century, only the Arctic experienced warming. It wasn't a global effect. This time, noted Ginny Catania, an expert on polar ice sheets and climate observations, the entire planet is warming and the size of the warming is many times larger.

Catania conducts research on Greenland's ice sheet. She described a research station on the northeastern part of the ice sheet that doesn't appear to be correlated with the AMO and yet has experienced twice the warming that the rest of the planet has in the past 150 years. This scale of warming is, however, predicted by global climate models that include human produced emissions of greenhouse gases.

Read the rest of the myths in this series ...

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