A Horrible Climate Mistake?

Source:  SPPI frozen earth2

by Lee C. Gerhard

Climate Cassandras may have made a monumental, horrible, mistake. Using the rubric that humans dominate natural dynamic earth processes, they and the popular media argue that the warming of the Arctic portends disaster for polar bears and humanity, although the world as a whole is not warming.  They focus on the unscientific premise that continuing rise in carbon dioxide concentration portends future societal disasters, calamities and debacles.

We scientists have known since 1896 that increased carbon dioxide has a greatly diminished effect on temperature. At today?s carbon dioxide concentration only a tiny effect can ensue even if the concentration doubles. But that is not their likely horrible mistake. The mistake is stating that air temperature, surface temperature, is the reason that sea ice is thinning in the Arctic.  It may be thinning from below, with huge implications for society.

There have been four continental-scale ice expansions over recent geologic history, with many smaller waxings and wanings within each. Each major ice advance has been somewhat less extensive than the previous.

In the early 1960?s, Maurice Ewing and William Donn presented a theory of the origin of continental glaciers that still makes sense today. They argued that to construct continental ice sheets in the northern hemisphere, a very large source of moisture to make snow is required. What could be this source?

There is only one answer possible: the Arctic Ocean must be ice-free. Evaporation of water from an ice-free Arctic Ocean permits accumulation of snow in high latitudes to make glacial ice. Gravity does the rest. Why then do continental glaciers wax and wane?

Ewing and Donn answered with a logical premise. When oceans are full, circulation is established between the warm North Atlantic and colder Arctic Oceans over the Greenland-Iceland sill, thawing the Arctic Ocean. This source of moisture permits ice sheets to build.  When enough water is evaporated, sea level drops, the circulation slows and then stills, letting the Arctic Ocean freeze over.  When frozen, the Arctic cannot sustain the ice sheets, and they melt back.

As ice sheets melt, sea level gradually rises, setting the stage for the next ice advance.  Some time in the future, equilibrium will be reached shutting down the glacial cycle. But that may be hundreds of thousands or millions of years away.

What if the current thinning of the Arctic Ocean ice cover, in contrast to the stable to cooling of the rest of the Earth, is coming from below, from warmer Atlantic water mixing into the Arctic?  Does this presage the next ice age?

Human society as we know it will not survive the next continental ice age. What if those Cassandras have made a horrible mistake?

Oh, the polar bears survived the prior glacial cycles and consequent ice waxing and waning just fine.  Not to worry.

State Geologist and Director (Ret.), Kansas Geological Survey

Senior Scientist Emeritus, University of Kansas

References:

Ewing, Maurice, and William L. Donn, 1956, A Theory of Ice Ages: Science, v. 123, n. 3207, 15 June 1956, 1061-1066.

Gerhard, Lee C., and William E. Harrison, 2001, Distribution of Oceans and Continents: A Geological Constraint on Global Climate Variability: in., Gerhard, Lee C., William E. Harrison, and Bernold M. Hanson, eds., 2001, Geological Perspectives of Global Climate Change: American Assoc. of Petroleum Geologists Studies in Geology #47, Chapter 3, p. 51-82.