Jet Propulsion Laboratory – November 13, 2007
Here we go again! It seems like every time we turn around there is a new study that suggests that global warming is going to get worse or it is going to reverse. The only clear evidence that I can find is that the climate is so complex that we simply don’t understand it yet.
A team of scientists for NASA has released a study that suggests that the Arctic Ocean circulation is about to change directions. It appears to do this somewhat frequently although it is doubtful that we really understand what transpired prior to the middle of the 20th century.
What does this mean? There are a lot of theories. I have heard that this will mean a return to more predominant La Nina conditions but that appears to be more conjecture than good solid science. Frankly, I don’t think we know what this means. Hopefully we will have some good solid scientists apply scientific methods to get closer to a working hypothesis.
Why do the currents reverse direction? I don’t know and I don’t think anyone else really does either. Another interesting area for scientists to research as it appears that it could have dramatic effects on the global climate models that are used to forecast the climate conditions in the future.
A team of NASA and university scientists has detected an ongoing reversal in Arctic Ocean circulation triggered by atmospheric circulation changes that vary on decade-long time scales. The results suggest not all the large changes seen in Arctic climate in recent years are a result of long-term trends associated with global warming.
The distribution and size of the decrease suggest that Arctic Ocean circulation changed from the counterclockwise pattern it exhibited in the 1990s to the clockwise pattern that was dominant prior to 1990.
“Our study confirms many changes seen in upper Arctic Ocean circulation in the 1990s were mostly decadal in nature, rather than trends caused by global warming,” said Morison.
The Arctic Oscillation was fairly stable until about 1970, but then varied on more or less decadal time scales, with signs of an underlying upward trend, until the late 1990s, when it again stabilized. During its strong counterclockwise phase in the 1990s, the Arctic environment changed markedly, with the upper Arctic Ocean undergoing major changes that persisted into this century. Many scientists viewed the changes as evidence of an ongoing climate shift, raising concerns about the effects of global warming on the Arctic.
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Filed under: Weather science