By Jim Steele

Daniel Swain is a good meteorologist but being a protégé of infamous climate alarmists like Noah Diffenbaugh and Michael Mann, he frequently spreads climate alarmists’ propaganda. His latest paper pushes the narrative that global warming is increasing dangerous “Hydroclimate Whiplash” fear mongering there is a increasing shift between wet years and dry years.

While wet years are confidently determined by measuring precipitation, dry years are determined by estimating changes in evapotranspiration which cannot be measured directly. There is no change the variability of precipitation during California’s rainy season. The inability to measure evapotranspiration creates great uncertainty in Swain’s estimation of dryness trends and his so-called whiplash effect.

Swain argues that floods and droughts are made worse by global warming because a warmer atmosphere can hold more water vapor. However, that is an irrelevant science factoid. The huge flaw in his argument is that the atmosphere cannot absorb any more water vapor no matter how warm, if the moisture isn’t available.

Moisture availability depends on the dynamics that transport water from the oceans to the land. Simply consider the fact that despite very warm temperatures in the Sahara Desert, its warmer temperatures do not increase the rates of desert precipitation or rates of evaporation. It is the Sahara’s dryness that causes such hot temperatures.

First consider that natural El Nino-La Nina Oscillations (graphic A) are a major driver of the earth’s wetness-dryness variability. While an El Nino event brings heavy rains to the western America, it causes drought in Indonesia. El Nino events happen every 3 to 7 years causing natural inter-annual wet-dry variability. Furthermore, El Nino activity has increased over the past 6000 years as global climate has cooled, long before any changing trends can be explained by rising CO2. The Pacific Ocean also experiences El Nino-like conditions that last 20-30 years before switching to La Nina-like conditions, the Pacific Decadal Oscillation.

El Nino-La Nina oscillations also drive the Indian Ocean Dipole (graphic B), causing extreme wetness that alternates between eastern Africa and the Indonesian Islands. El Nino-La Nina Oscillations also affect climate in the Atlantic by strengthening or weakening the North Atlantic’s subtropical high pressure (graphic C). La Nina events strengthen the pressure system moving its center westward.

That shift causes wetter conditions in the eastern United States as atmospheric circulation drives more moisture westward. In contrast El Nino events weaken the pressure system causing drier conditions by shifting rainfall eastward.

Finally consider the Intertropical Convergence Zone (ITCZ graphic E) as a major driver of natural wetness-dryness variability. The ITCZ forms where northern and southern trade winds converge. That convergence drives moisture laden air upwards where it cools so that the moisture rains out. Over 30% of the earth’s rainfall happens beneath the ITCZ. The remaining air is now dry and circulates to the north and south. Where that dry air descends, it brings dry weather which generates most of the world’s deserts.

The ITCZ moves north and south mostly following the seasonal path of the sun’s direct rays (graphic F). As graphic D shows, the ITCZ’s position has shifted over thousands of years as well as over decades. As a result of the ITCZ’s more northerly location, more moisture reached the Sahara, transforming it into a lake-filled savannah supporting abundant wildlife and human tribes. As the ITCZ migrated southward as the earth cooled starting 6000 years ago, fewer rains reached the Sahara re-creating a desert.

Likewise, ITCZ migrations affect where monsoon wetness will occur. In addition, the ITCZ affects the intensity of El Nino and La Nina.

Swain sadly ignores these major drivers of natural wetness-dryness variability, preferring to blame global warming. Thus, Swain and his fellow climate alarmists fail to educate the public about the known reasons for natural wetness-dryness variability. Addicted to a belief in a global warming climate crisis, alarmists prefer to blame a warmer atmosphere’s ability to hold more water vapor. Thus, they can conveniently maintain their crisis narrative that paradoxically argues CO2 warming can cause both wetter and drier conditions and dry the landscape causing more fires. It is bad science, dedicated to pushing a bogus climate crisis agenda.