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Freshwater’s Effects On Global Warming

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Did a very large and unexpected flux of freshwater into the Northern Hemisphere’s oceans in the late 1960s and early 1970s temporarily slow down global warming?  That very well might be the case, according to an article in a recent issue of Nature.  The authors have noted that a temporary 0.3C decrease in Northern Hemispheric sea-surface temperatures “corresponded with a ‘great salinity anomaly’ that took place in the late 1960s and early 1970s, when a pulse of cold water flowed from the Arctic into the northern Atlantic Ocean.”

It is events like this and their cascading series of results that make extremely accurate climate modeling and forecasting challenging.  Which leads to an obvious question: as Northern Hemispheric land-based glaciers melt at accelerating rates, how will the resulting large flux of freshwater affect global temperatures in the 21st century?  There is emerging research in this realm as well.

Many researchers have predicted that climate change will speed up the water cycle – increasing precipitation, evaporation and river discharge, bringing more frequent and intense extreme events like flooding and drought, and causing more rain at high and low latitudes but less rain in the mid-latitudes.

These kinds of trends are beginning to become more apparent.  2010 was in some ways a case study, in fact.  Devastating heat waves, flooding resulting from long-lived, intense rain systems, widespread record snowfalls and continuing, intense droughts.  It’s not a stretch to say that these kinds of events are probably going to present themselves more and more going forward.

The biggest problem with freshwater’s potential effects on the climate system?  There isn’t a global, comprehensive monitoring network established; nor is one even planned.  Without the ability to observe the hydrologic cycle at a rudimentary level, projecting changes to the cycles’ effect on climate remains nearly impossible.


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