By William M. Gray prepared for the Heartland ICCC

This paper discusses how the variation in the global ocean’s Meridional Overturning Circulation (MOC) resulting from changes in the Atlantic Thermohaline Circulation (THC) and deep water Surrounding Antarctica Subsidence (SAS) can be the primary cause of climate change.  (MOC = THC + SAS) is the likely cause of most of the global warming that has been observed since the start of the industrial revolution (~1850) and for the more recent global warming that has occurred since the mid-1970s.  Changes of the MOC since 1995 are hypothesized to have lead to the cessation of global warming since 1998 and to the beginning of a weak global cooling that has occurred since 2001.  This weak cooling is projected to go on for the next couple of decades.

Recent GCM global warming scenarios assume that a slightly stronger hydrologic cycle (due to the increase in CO2) will cause additional upper-level tropospheric water vapor and cloudiness.  Such vapor-cloudiness increases are assumed to allow the small initial warming due to increased CO2 to be unrealistically multiplied 2-4 or more times.  This is where most of the global warming from the GCMs comes from - not the warming resulting from the CO2 increase by itself but the large extra warming due to the assumed increase of upper tropospheric water vapor and cloudiness.  As CO2 increases, it does not follow that the net global upper-level water vapor and cloudiness will increase significantly.  Observations of upper tropospheric water vapor over the last 3-4 decades from the National Centers for Environmental Prediction/National Center for Atmospheric Research (NCEP/NCAR) reanalysis data and the International Satellite Cloud Climatology Project (ISCCP) data show that upper tropospheric water vapor appears to undergo a small decrease while Outgoing Longwave Radiation (OLR) undergoes a small increase.  This is opposite to what has been programmed into the GCMs.  The predicted global warming due to a doubling of CO2 has been erroneously exaggerated by the GCMs due to this water vapor feedback.

CO2 increases without positive water vapor feedback could only have been responsible for about 0.1-0.2C of the 0.6-0.7C global mean surface temperature warming that has been observed since the early 20th century. Assuming a doubling of CO2 by the late 21st century (assuming no positive water vapor feedback), we should likely expect to see no more than about 0.3-0.5C global surface warming and certainly not the 2-5C warming that has been projected by the GCMs.

Full paper available here (under News). See comments from Richard Courtney on Bill’s paper here.