Have Increases in CO2 Contributed to the Recent Large Upswing in Atlantic Basin Major Hurricanes Since 1995?
Publisher Summary It is not possible to directly measure the strength of the thermohaline circulation (THC). But its strength can be inferred from proxy measurements of the North Atlantic SST and salinity anomalies (which are directly related to each other) minus the sea level pressure anomaly (SLPA) over the broad Atlantic (0–50°N; 70°W–10°W). When the THC is strong, the Atlantic atmospheric and oceanic subtropical gyres are weaker than normal. When the Atlantic THC is weaker than average, the gyres are stronger than normal. With regards to multidecadal variations of Atlantic major hurricane activity, it is possible to give a sequence of physical arguments for how a year or a multidecadal period with a stronger than normal THC will have tropical Atlantic conditions associated, which are more favorable for Atlantic basin major hurricane activity. Among these conditions are positive tropical Atlantic sea surface temperature anomaly, lower tropical Atlantic SLPAs, weaker trade winds, and smaller values of tropospheric vertical wind shear. There is no evidence that Atlantic hurricane activity is significantly impacted by CO2 increases or by global mean surface temperature changes. This myth should be put to rest. It is the natural variability of the Atlantic's meteorological parameters that one must be concerned about.