Evidence mounts on climate change

But there is still time to mitigate the damage.

Conservationist and adventurer Tim Flannery starts his new book, The Weather Makers, by acknowledging the huge task before him: taking the "Chicken Little" out of the words "climate change" and making people care.

"One of the biggest obstacles to making a start on climate change," he writes, "is that it has become a cliché before it has even been understood."

It is such honest and spirited writing that makes this book a compelling read, and one that could melt public ambivalence. Flannery (whose other books include "The Eternal Frontier" and "The Future Eaters") deftly brings the complex field of climate science and its components such as greenhouse gases and global warming within reach of the lay reader.

In three simple sentences he clarifies the terms: "Greenhouse gases are a class of gases that can trap heat near Earth's surface. As they increase in the atmosphere, the extra heat they trap leads to global warming. This warming in turn places pressure on Earth's climate system and can lead to climate change."

He also distinguishes between weather, which is what we experience daily, and climate, weather over a certain period for a region or the whole planet.

To explain the evidence that climate change exists, he takes us globetrotting to various regions and times in history and discusses, in plain language, specific changes over long periods of time that are concerning scientists.

Take the drought in the American West. While some have attributed it to being part of a natural cycle, Flannery takes the bird's-eye view, pointing to changes in snowpacks high up in the mountains that are worrying climatologists.

Water that melts from mountain snowpacks fills streams flowing to the land below. Over the past 50 years, however, there has been a decline in the average snowfall, and if the trend continues 50 more years, Western US snowpacks could be reduced by up to 60 percent. That means some summertime stream flow could be cut in half, impacting water supplies, hydropower, and fish habitats.

The volume of snowfall, however, isn't as unsettling as changes in the way snowpacks form and melt. Over the past 50 years, the southwest region has warmed by 1.4 degrees F. While that doesn't sound like much - it's slightly more than the global average - it is melting the snowpack earlier, so peak runoff of water into streams is happening three weeks sooner than in 1948. That means less water in summer, when it is most needed, and more water in winter, which may cause flooding.

"With temperatures in the region set to rise between 3.6 degrees Fahrenheit and 12.6 degrees Fahrenheit over this century (unless we significantly reduce CO2 emissions), it can be anticipated that most streams will eventually flow in winter, when the water is least needed," he writes. Ultimately this could lower farm values by 15 percent, costing billions of dollars, and reduce water supplies to Western US cities.

There is a growing body of such scientific evidence to support the conclusion that climate change is really happening. One key piece of scientific evidence is a sample extracted from two miles into the Antarctic ice cap in June 2004. The ice core lets researchers look back at least 740,000 years in time and study Earth. Of particular interest is about 430,000 years ago, when our planet was in a position similar to the one it is in today.

The mix of detailed science and clear language will please both the casual reader and the arm-chair climatologist.

At times, Flannery gets a bit too alarmist, as in a chapter entitled, "The last act of God?" But overall, his detailed explanations of the science and impact of climate change are both educational and disturbing. We can feel for the gastric brooding frog, a species that nurtures its tadpoles in its stomach, and which may be Australia's (his home country) first victim of climate change.

And we can feel Flannery's wrath against the politicians and industrialists whom he believes are contributing to the planet's problems.

Flannery completed writing the book just before hurricane Katrina hit the southern US six months ago. While scientists are still debating whether the increase in powerful hurricanes in the past decade is a result of climate change, Flannery says catastrophic events like Katrina do focus attention on climate change in a way few other natural phenomena do. Other dubious landmarks over the past 10 years: the most powerful El Niño ever recorded, the hottest European summer on record, and the first South Atlantic hurricane.

But Flannery doesn't leave the reader in hopeless despair. At the end of the book he provides a simple climate change checklist that shows us the direct consequences of our actions so we might change them.

For example, using energy-efficient appliances can reduce household emissions from electricity up to 50 percent. By explaining the history and science behind climate change, he builds a valuable stage from which individuals can act.

Lori Valigra is a freelance writer based in Cambridge, Mass.

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