Saturday, November 10, 2007

Mackenzie: climate perspective--Watch out!

Humankind has caused changes in every significant chemical process in the natural world, according to Fred Mackenzie, the University of Hawai'i oceanographer and geochemist who has done seminal work in issues involving the world's environment.

A lot, although not all of those changes, are directly tied to fossil fuel use.

“We must abate or mitigate fossil fuel use” or face planetary climate shifts that are potentially so fast and so powerful that we won't be able to respond effectively to them, he said.

Mackenzie gave a talk last week to a Big Island national conference of the National Science Foundation's EPSCoR project. EPSCoR is a program to promote scientific pursuit in the states that traditionally receive comparatively few NSF grants. Hawai'i is among them.

Today, the human impact on Earth's environment is as strong as any other force in the system, and the only thing more powerful, Mackenzie said, would be a meteor impact.

And the impact involves far more than just warming of the planet, he said.

As an example, there have been dramatic changes in what Mackenzie called the planet's “biogeochemical cycles.”

Before the Industrial Age, both carbon and sulfur tended to move from the oceans into the atmosphere. That pattern has reversed, with significant impacts, including making the oceans more acid.

His studies, Mackenzie said, show that shell-building and coral reef-building organisms do less of that when the ocean becomes more acid.

“Every experiment that we've done, when we've lowered the pH (made water more acid)...the organisms...have calcified at a lower rate,” he said.

As additional human-caused changes, Mackenzie cited high atmosphere ozone depletion, tropical deforestation, the loss of biological diversity and several more issues.

Mackenzie is rare among commentators in human environmental impacts because in many cases, he's the guy who has been doing the science.

He can tell you which pieces of the puzzle are significant, and which may not be. (Less-educated commentators, without the grounding in science, often throw out each fact as if it had equal value.)

For Hawai'i, for example, there are suggestions that continued climate change will make the Islands warmer. But Mackenzie argued “we can take that with a grain of salt because...of the variability of the data.”

Greenland's glaciers are a fine example of the need for perspective. The central mass of Greenland's glaciers are experiencing growth—more snow and ice. But the fringes of the glaciers are melting faster—less snow and ice.

Agenda-motivated commentators might focus on one or the other, but the fact is that both processes are happening at once. What's important is the net change, Mackenzie said, and the net is that the melting is bigger than the accretion.

The Greenland ice sheet as a whole is losing ice at the equivalent of a half a millimeter annually in sea level rise. If you extrapolate that out over a century (I did this calculation, not Mackenzie, so don't blame him) it's 50 millimeters, or about two inches.

That is, Greenland alone could be responsible for two inches of global sea level rise. And that number is not included in current estimates of sea level rise from the Intergovernmental Panel on Climate Change, since it's more recent than the data used by IPCC to come up with its conclusions.

A member of the conference audience asked about the impact of global dimming, the increase in particulate matter in the atmosphere, which reflects some solar radiation.

Said Mackenzie, dimming is real, but what's important for the planet is the net change. And the net change is that warming has continued over the past 150 years, in spite of dimming.

A number of the other scientists at the EPSCoR conference made reference to the allegory of the blind men and the elephant, in which people grasping at a small piece of the creature never guess the totality of what they have before them.

The key is perspective. Without taking the larger view, it's easy to make wrong assumptions.

© 2007 Jan W. TenBruggencate

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