Global Warming & Ozone: Sea Change?

Bet you haven't seen this story in the local paper or on tragedy-TV: Global warming may be about to slow down dramatically, if not completely. Further, a considerable portion of the warming of the last half of the 20th century may have been a "natural" internal oscillation of the Pacific Ocean.

This news comes from yet another blockbuster paper from the climate group at Texas A&M University. Last year, as covered in these pages, Gerry North and his colleagues demonstrated that sulfate aerosols don't cool the planet very much after all. That discovery disturbs most greenhouse apocalysts, especially our more global friends at the United Nations, who rely on sulfate aerosols to explain why the planet has warmed so little, compared with what (bad) computer models say should have happened. If sulfates aren't the reason, then it is likely that the carbon dioxide warming effect is just plain overestimated.

(Just this week, Yangang Liu and Peter Daum calculated in Nature that the cooling effect from sulfate-induced cloudiness, the so-called "indirect sulfate effect" has been overestimated by 10 percent to 80 percent, yet another nail in the coffin of the global warming apocalypse.)

In the most recent A&M shocker, Amy Bratcher and Benjamin Giese show that the vaunted sudden warming of the mid-1970s, known as "the great Pacific Climate shift," resulted when a warm pool of subsurface water generated in the Southern Ocean finally joatered to the top near New Guinea. Once this happens, currents move the tepid stuff rapidly eastward, and the surface temperature responds in a few years.

This is important because about half of the warming of the last 50 years is contained in the sudden 1976–1977 shift, and there's no model of human-induced warming that produces such sudden changes.

But, you would think, if humans didn't cause the mid-1970s shift, then it's likely that there would be some other compensating cooling in subsequent decades. Otherwise global temperatures would progress up and up and up (or down and down and down) much more enthusiastically than they do.

Bratcher and Giese write:

The possibility exists that some portion of the recent increase in global surface air temperature is part of a naturally oscillating system. Examples of such natural variations are prominent in the tropical Pacific Ocean…A sudden change in the climate of the tropical and north Pacific Ocean during 1976 has been extensively documented…Recent work suggests that the origin of this climate shift comes from the Southern Hemisphere and may be part of a naturally oscillating climate pattern [emphasis added].

So, where's the cooling? It's right around the corner! Bratcher and Giese show that a big pool of cold water, about the same size and magnitude as the warm one that caused the 1976 shift, is about to surface in the western Pacific. Their calculations suggest that the cooling will become evident within the next few years. Strictly speaking (something no one in the climate business has any business doing), the cooling should start in 2003.

Figure 1. Red line: Subsurface water temperature in the Southern Ocean. Blue line: Sea-surface temperature in the Central Pacific, lagged by seven years. Forecast: Clearing and cooler!

Even your pals at WCR wouldn't have the guts to write that paper, but if it's right, temperatures will drop about 0.2°C in the next few years.

What a mess this could cause! Take away this factor from the roughly 0.5°C of the last 30 years, and finally admit that sulfate aerosols are, at best, also-rans, and that leaves a greenhouse warming rate of about 0.1° per decade. Given that the consensus of most climate models (ironically, not verbalized by most climate modelers) is that once greenhouse warming starts, it takes place at a constant rate, this gives a mere 1.0°C of warming for the coming century.

The Bratcher and Giese bomb dropped in the midst of another shocker, which is the amazing, disappearing ozone hole. Of course, we've always maintained that "ozone hole" was a misnomer and should more correctly be called the "late winter Antarctic ozone depletion" (LWAOD) because it is most prominent only for a few weeks of the year, and once the sun gets high enough in the sky to bust up stratospheric oxygen molecules, most of the ozone returns.

It turns out that to everyone's surprise, this year's edition of the LWAOD is the smallest in 15 years, which isn't many years after the LWAOD first became prominent.

NASA scientists indicate that the cause of this year's weenie hole is an unusually warm Antarctic stratosphere. WCR scientists would like to point out that greenhouse warming, which takes place in the lower atmosphere, commands a compensatory cooling of the stratosphere.

You just have to wonder if the ozone and climate shift stories aren't a bit related. Is the fact that the stratosphere has suddenly warmed a result of the equally sudden appearance of the big Pacific chill? Stay tuned.

Figure 1. Maximum size of the Antarctic ozone hole, 1980 to 2002.

Oh, and don't go crediting the Montreal Protocol on ozone-depleting chemicals for this change—observed concentrations of those compounds haven't dropped enough to effect this year's change in stratospheric ozone. And never credit the Kyoto Protocol on global warming for anything having to do with climate, because it will never have a detectable effect on anything except our economic well-being.

References:

Bratcher, A., and B. Giese, 2002. Tropical Pacific decadal variability and global warming. Geophysical Research Letters, 29, 24-1–24-4.

Liu, Y., and P.H.Daum, 2002. Indirect warming effect from dispersion forcing. Nature, 419, 580–581.

North, G.R., and Q. Wu, 2001. Detecting climate signals using space-time EOFs, Journal of Climate, 14, 1839–1863.