AWRA Water Blog

Wally’s Warming World Warning

Time for a shout-out to a remarkable scientist (thanks to columbiawater for alerting me to this).

Wally Thirty-five years ago, on this date in 1975, renowned geoscientist Wallace (Wally) Broecker published a seminal paper in Science titled,Are We on the Brink of a Pronounced Global Warming?“. To say that Broecker was prescient is an understatement.

 Here is the abstract:

If man-made dust is unimportant as a major cause of climatic change, then a strong case can be made that the present cooling trend will, within a decade or so, give way to a pronounced warming induced by carbon dioxide. By analogy with similar events in the past, the natural climatic cooling which, since 1940, has more than compensated for the carbon dioxide effect, will soon bottom out. Once this happens, the exponential rise in the atmospheric carbon dioxide content will tend to become a significant factor and by early in the next century will have driven the mean planetary temperature beyond the limits experienced during the last 1000 years.

Over at Foreign Policy Brad Johnson has an informative article, “Wally’s World,” not only about Broecker, but also a brief history of the work of those who set the stage for Broecker and those who came after him. It’s global warming in a nutshell. See also this post from Andrew C. Revkin.

Here is an interview with Broecker, who coined the term ‘global warming’ and is regarded by many as the father of climate science. He is 78 and still going strong at Columbia University and The Earth Institute.

I knew of Broecker long before I knew of global warming; I cited some of his work in my dissertation. Broecker was one of the pioneers of radiocarbon and isotopic dating and I used carbon-14 and tritium dating of groundwater in my tome, Finite-State Models of Transport Phenomena in Hydrologic Systems (Pretentious? Moi?), which I was completing about the time Broecker’s paper appeared. I confess I did not read the paper until almost 15 years later.

I had the distinct pleasure of meeting and chatting with him in the early 1990s when he spoke at one of our E&PS seminars at the University of New Mexico. He was a terribly nice fellow. His topic was something with which I was unfamiliar: the disruption of the North Atlantic’s thermohaline-driven ‘ocean conveyor belt’ (which he first recognized) that brought heat from the tropics to the northernmost Atlantic and kept northern Europe from having a climate like Siberia’s. Brocecker posited that if global warming melted enough of the polar icecaps, the northernmost Atlantic would freshen, thus weakening, and possibly terminating, this heat transfer mechanism, thus plunging northern Europe into a freeze. It has happened in the past.

I thought that was quite remarkable: global warming leading to dramatic cooling in one part of the world (here’s an article by Robert B. Gagosian on this topic). But that’s the nature of global warming: worldwide, average temperatures rise, but not every region warms.

Broecker also noted that these climate changes occurred rather abruptly:

The climate system has jumped from one mode of operation to another in the past. We are trying toOcci_abrclimate_wef_n_19062 understand how the earth’s climate system is engineered, so we can understand what it takes to trigger mode switches. Until we do, we cannot make good predictions about future climate change… Over the last several hundred thousand years, climate change has come mainly in discrete jumps that appear to be related to changes in the mode of thermohaline circulation. We place strong emphasis on using isotopes as a means to understand physical mixing and chemical cycling in the ocean, and the climate history as recorded in marine sediments.

I’ll never forget Broecker’s talk, lucidly and cogently presented. It was in the pre-Power Point era so he used transparencies and slides. He had some simple cartoons, and his closing transparency, showing a ferocious dragon-like creature with some humans annoying it, bore these words that have remained with me ever since:

“The climate system is an angry beast, and we are poking at it with sticks.” — Wallace S. Broecker, Albuquerque, NM, c. 1991

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