Various sources, scientists publishing their opinion in the media, claim that Tropical Storm Harvey, recently landed in Texas, is one more signal of the influence of global warming on such catastrophic events. These claims are based on model calculations. Let’s examine the facts.

In the Atlantic Ocean, sea surface temperature oscillations are observed as a multidecadal cycle (AMO).

The total energy accumulated each year by tropical storms and hurricanes (ACE) is also showing such a cyclic pattern.

NOAA’s Hurricane Research Division explanations on ACE: “the ACE is calculated by squaring the maximum sustained surface wind in the system every six hours (knots) and summing it up for the season. It is expressed in 10⁴ kt².” Direct instrumental observations are available as monthly series since 1848. A historic reconstruction since 1851 was done by NOAA (yearly means).

A correlation between ACE and AMO is confirmed by regression analysis.

Regression formula:

ACE_calc = 99.58 + 142.75*AMO_7y + 40.11*delay(AMO_7y,18)
Pearson R2 = 0.9245

Thus, a simple, linear relation ties ACE to AMO, in part directly, and in part with an 18 years delay. The correlation coefficient is astonishingly good.

Origin and mechanisms directing AMO are quite unknown. Therefore, any speculation aiming at associating cyclone energy with other phenomena, as e.g. anthropogenic climate warming, would need a clear and cut irrefutable proof. Model speculations cannot serve as proof without full validation.