January 04, 2007

Environmental Feedback

Sir James Lovelock first postulated the Gaia hypothesis in the 1960's. What he hypothesized was that the earth was very adept at regulating its surface conditions (particularly the amount of carbon dioxide in the atmosphere) leading it to be very conducive to life.

Today, the idea that the earth acts like a living organism is not so farfetched. One thing that he based the hypothesis on was how remarkably stable our earth's atmosphere and oceans have been considering the external pressures.

Lovelock and Margulis, considered coauthor of the Gaia theory, soon discovered other bits of "good fortune." Although the sun has strengthened steadily, the Earth's surface temperature has stayed comfortable for life for hundreds of millions of years. The same for oceanic salinity, which remains far below the saturation point and well below concentrations lethal to aquatic life, even though millions of tons of salt run off into the oceans and seas each year.

As Bill McKibben discusses in his recent piece in the New York Books of Books, we humans (and the rest of life on earth) have been remarkably fortunate to live on a planet that has been able to regulate the environment so well for hundreds of millions of years.

Putting aside questions of planetary consciousness and will (beloved as they were by an early wave of New Age Gaia acolytes), the theory may help us understand how the earth has managed to remain hospitable for life over billions of years even as the sun, because of its own stellar evolution, has become significantly hotter. Through a series of processes involving, among others, ice ages, ocean algae, and weathering rock, the earth has managed to keep the amount of heat-trapping carbon dioxide in the atmosphere, and hence the temperature, at a relatively stable level.

This homeostasis is now being disrupted by our brief binge of fossil fuel consumption, which has released a huge amount of carbon dioxide into the atmosphere. Indeed, at one point Lovelock predicts—more gloomily than any other competent observer I am aware of—that we have already pushed the planet over the brink, and that we will soon see remarkably rapid rises in temperature, well beyond those envisioned in most of the computer models now in use—themselves quite dire. He argues that because the earth is already struggling to keep itself cool, our extra increment of heat is particularly dangerous, and he predicts that we will soon see the confluence of several phenomena: the death of ocean algae in ever-warmer ocean waters, reducing the rate at which these small plants can remove carbon from the atmosphere; the death of tropical forests as a result of higher temperatures and the higher rates of evaporation they cause; sharp changes in the earth's "albedo," or reflectivity, as white ice that reflects sunlight back out into space is replaced with the absorptive blue of seawater or the dark green of high-latitude boreal forests; and the release of large amounts of methane, itself a greenhouse gas, held in ice crystals in the frozen north or beneath the sea.

All of these effects are worrying, but the biggest wildcard -- the one that threatens to make global warming so extreme that life will have a significant problem surviving the consequences -- is the last one: the release of methane gas.

For years climate scientists that have been concerned with the increased buildup of carbon dioxide in the atmosphere and have been urging action to reduce the carbon dioxide emissions contributed by humans. They thought that if humans reduced their carbon dioxide emissions, the earth would once more balance and regulate its surface to maintain a life-viable system.

Yet, last year some of the global warming studies have provided some truly worrying information about how close we are to tripping (or disabling) the earth's natural regulator mechanisms. The problem no longer is how much carbon dioxide humans emit (although we have been doing a yeoman's job of trying to overwhelm the system), it's whether the earth starts to release the vastly greater amount that's been trapped in the earth for millions of years.

A study released earlier this year in Science foreshadowed these latest findings. The yedoma, it said, represent a vast reservoir of carbon neglected in most analyses of climate change. An estimated 500 gigatons of carbon have been flash frozen in yedoma regions and 900 tons in permafrost worldwide. If released, this store would more than double the amount of carbon in the atmosphere today.

The fear is that the thawing lake region, which comprises 90 percent of the Russian permafrost zone, will dump methane into the atmosphere at a rate that will dwarf any human attempts to curtail carbon dioxide emissions.

This is worrying in two ways: 1) if the earth warms enough to slowly release the trapped methane gas from permafrost and from the depths of the ocean, even if humans completely stopped emitting carbon right now, the earth still could not adjust because the effect of the methane gas would totally swamp all human emissions; and 2) a rapid release of methane gas could lead to a massive die-off of life both on earth and in the oceans.

Geologists have tied the rapid release of methane gas to the most extreme die-offs the earth has ever experienced.

There are enormous quantities of naturally occurring greenhouse gasses trapped in ice-like structures in the cold northern muds and at the bottom of the seas. These ices, called clathrates, contain 3,000 times as much methane as is in the atmosphere. Methane is more than 20 times as strong a greenhouse gas as carbon dioxide.

Now here's the scary part. A temperature increase of merely a few degrees would cause these gases to volatilize and "burp" into the atmosphere, which would further raise temperatures, which would release yet more methane, heating the Earth and seas further, and so on. There's 400 gigatons of methane locked in the frozen arctic tundra - enough to start this chain reaction - and the kind of warming the Arctic Council predicts is sufficient to melt the clathrates and release these greenhouse gases into the atmosphere.

Once triggered, this cycle could result in runaway global warming the likes of which even the most pessimistic doomsayers aren't talking about.

An apocalyptic fantasy concocted by hysterical environmentalists? Unfortunately, no. Strong geologic evidence suggests something similar has happened at least twice before.

The most recent of these catastrophes occurred about 55 million years ago in what geologists call the Paleocene-Eocene Thermal Maximum (PETM), when methane burps caused rapid warming and massive die-offs, disrupting the climate for more than 100,000 years.

The granddaddy of these catastrophes occurred 251 million years ago, at the end of the Permian period, when a series of methane burps came close to wiping out all life on Earth.

More than 94 percent of the marine species present in the fossil record disappeared suddenly as oxygen levels plummeted and life teetered on the verge of extinction. Over the ensuing 500,000 years, a few species struggled to gain a foothold in the hostile environment. It took 20 million to 30 million years for even rudimentary coral reefs to re-establish themselves and for forests to regrow. In some areas, it took more than 100 million years for ecosystems to reach their former healthy diversity.

That report from EnergyBulletin was written before the most recent studies measuring the release of methane gas were published. No wonder scientists are becoming really worried about global warming and our inability to deal with it.

"Things are happening now almost faster than we can predict them," says Richard Gammon, a UW chemistry and oceanography professor. "Right now, the scientists are more alarmed than the general public."


"One key goal of this book ["Hell and High Water"] is to provide a fuller answer to the puzzle of why this country has failed to act on global warming," he writes, adding that the change required today will only come with public outrage. "My hair is on fire. And yours should be, too."

We really don't have time to argue any longer about whether or not global warming is happening. Global warming is the crisis of our generation and so much more serious than terrorism. It's time we spent our time and energy on what really matters. We've been lucky to have an earth that adjusts to be habitable, so let's do our part to make it easier for it to continue to do so. After all, the consequences of being wrong are really unimaginable.

Posted by Mary at January 4, 2007 07:30 AM | Environment | Technorati links |