Guest contribution by Steinn Sigurdsson.
Recently, there have been some suggestions that “global warming” has been observed on Mars (e.g. here). These are based on observations of regional change around the South Polar Cap, but seem to have been extended into a “global” change, and used by some to infer an external common mechanism for global warming on Earth and Mars (e.g. here and here). But this is incorrect reasoning and based on faulty understanding of the data.
Just recently, RealClimate topped 500,000 visits (and well over a million page views) since starting in December 2004. And by happy coincidence, a present arrives in the form of RealClimate being selected for the “Science & Technology Web Awards 2005” by Scientific American, with the citation:
A refreshing antidote to the political and economic slants that commonly color and distort news coverage of topics like the greenhouse effect, air quality, natural disasters and global warming, Real Climate is a focused, objective blog written by scientists for a brainy community that likes its climate commentary served hot. Always precise and timely, the site’s resident meteorologists, geoscientists and oceanographers sound off on all news climatalogical, from tropical glacial retreat to “doubts about the advent of spring.”
In a recent (of Sept. 16, 2005) publication in Science, Hatun et al. find that record-high salinities have been observed over the past decade in the region where water from the Atlantic flows into the northern oceans. They combine an analysis of observations with simulations using an ocean model, concluding that the salinity of the inflow to the northern oceans is controlled by ocean dynamics and the circulation in the sub-polar gyre. The observations by Hatun et al. may suggest that at the moment the warm and salty waters from the south are especially warm and salty.
In another publication paper in Science from June 17th 2005, on the other hand, Curry & Mauritzen conclude that as a whole the northern North Atlantic has become significantly fresher (less salty) in recent decades. The latter study was based entirely on observations (hydrographic data between Labrador and Europe in the past 50 years). The recent evidence for salinification provided by Hatun et al. has been interpreted by some as being inconsistent with the evidence for high-latitude North Atlantic freshening found in previous reports. So what is really happening? Is the salinity increasing or decreasing? And can the two recent Science studies be consistent with each other?
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