As the World Melts

Wired
By John Gartner
Jun, 30, 2006

It's no secret that the Earth is getting hot. A recent National Academy of Sciences study finds that the warming of the northern hemisphere in the last decades of the 20th century was unprecedented in the past thousand years.

Most experts studying the recent climate history agree that human activities -- mainly the release of heat-trapping gases from smokestacks, tailpipes and burning forests -- are probably to blame.

Without big curbs in greenhouse-gas emissions, climate change could lead to continued temperature increases, dramatic shifts in weather patterns, shrinking ice sheets and rising seas. These changes could spell catastrophe for most of the world's glaciers and threaten supplies of fresh water in the most populous regions on Earth.

Wired News spoke with Lonnie Thompson, an Ohio State University professor and paleoclimatologist who has spent the last 31 years studying the ice fields atop many of the world's highest peaks. Thompson analyzes the long frozen ice cores stored within glaciers to discover how the chemical composition of the Earth's atmosphere has changed since the last ice age, and how it affects the climate.

Wired News: What is paleoclimatology and how did you become interested in it?

Lonnie Thompson: Paleoclimatology is the study of the past climate of the Earth as it is recorded in various recorders such as lake sediments, corals and ice. During my first year (at Ohio State University) I saw an opening in the Institute of Polar Studies to look at ice cores. I had dismissed glaciers as not important because they only cover 10 percent of the Earth's surface and few people live there, but I took the job because I wanted a research position.

WN: What can you learn from studying ice cores obtained from glaciers at high altitudes that you can't from exploring the polar regions?

LT: The Earth is a sphere, and 50 percent of the surface area is located in the tropics between 30 degrees north and south, and 70 percent of the people on the planet live there. Some of the big climate forcings, such as El Niño-Southern Oscillation events and changes in monsoon seasons, are tropical phenomenon, so to get the long-term history you have to look at the archive in the tropical locations.

Only by looking at the past and documenting the natural changes can we get the real perspective on how unusual today's climate is.

WN: What does the chemical composition of an ice core tell us about historical climate change?

LT: Learning about yearly changes in climate enables us to recover the history from where we have virtually no written records and understand how the climate system has changed between the last ice age (over 10,000 years ago) and now. We can see the temperature changes between summer and winter and at different latitudes across the planet.

The air bubbles trapped in the ice cores tell us a history of the composition of Earth's atmosphere and give us a time perspective of the CO2, methane, and nitric oxides that we are concerned about today. The cores are also archives of the chemistry of the atmosphere. You can see when lead was put into the gasoline, and when it was later taken out. We use the archive to document how the climate varied before humans became a major factor.

WN: How do you obtain the ice core samples and what technology do you use to analyze them?

LT: We drill though hundreds of meters of ice to get to the cores that have been frozen underneath for many years. The challenge is keeping the cores frozen until they get back to the university.

At Ohio State we … use mass spectrometers to analyze the isotopes of hydrogen and oxygen that make up the molecules of water. Chemistry on these same samples is measured using an ion chromography while dust is measured with a particle counter. We have the only archive of tropical ice cores, which is important because many of these glaciers will melt within the next 15 years.

WN: How have your expeditions changed your understanding of the Earth's temperature fluctuations?

LT: When CO2 was lower in the past, such as at 180 ppm (parts per million of the atmosphere), the Earth was in the grips of an ice age. During warm periods, CO2 rose to about 280 ppm…. We are currently at 380 ppm of CO2, and there is no analogy for this.

In the tropics what has happened in the past few years for snow melt is very unusual in the last 2,000 years where we have this detailed history. The ice fields in the Himalayas in Asia and the Andes in Peru are retreating at an accelerated rate. For example, the rate of retreat at the Quelccaya ice cap was 6 meters per year from 1963 to 1978, but from 1991 to 2005 it is retreating at 60 meters per year. The melting there has uncovered plants, that through carbon dating, we realize have been frozen for more than 6,500 years, which tells us the last time the ice fields were this small.

WN: Based on your research of studying climate change, how do you expect the weather patterns to change during the next 20 years?

LT: The changes in the greenhouse gas composition indicate that we are in for some marked changes. We don't know the specific areas, the magnitude of the changes or the timing. But it's similar to when you go to the doctor and he says that you have a high blood pressure and are subject to a heart attack. He's not going to tell you when that is going to occur, but the symptoms are so pervasive that you know you are at risk.

We have already built in an additional rise in temperature of 0.6 degrees centigrade, which is causing the glaciers to disappear. The melting in the Himalayas has tremendous implications for the 2 to 3 billion people who live downstream from rivers such as the Ganges, Indus and Yangtze that are fed by the glaciers there. These people will have less water to use as a municipal source and for hydropower and irrigation. The scary thing is the impact of the climate changes that we don't know, for example, how it will affect the insects that inhabit and can devastate our forests.

WN: Skeptics of global warming say the current warming trend is just another cyclical fluctuation and not from our use of fossil fuels. How do you respond to that?

LT: When you look at the history of CO2, methane and nitric oxide in the atmosphere, the levels are not something that we have seen in the long history of our ice cores now spanning over 650,000 years. Sure, the temperature of the planet has changed in the past with ice ages.... But these changes in climate were slow, while what we are seeing right now is a rapid change.

Now the increase of greenhouse gases and land-usage changes have a tremendous impact on the planet, so we have to be very careful how much we tweak the system. With 6.5 billion people living on the planet, even the natural variations will have tremendous economic impact on all of us.

WN: Is it true you don't like mountain climbing?

LT: Yes that's right. I've learned only what I have to learn to get to our field sites. For these projects we have to move six tons of equipment up to the summit of these mountain ranges, and to do this we often have to cross crevasse fields and avalanche fields, so we need to know mountaineering in order to minimize the risks in getting the crew in and out and the ice cores out.

What makes us different from mountaineers is that we look for the easiest and safest way to get to where we need to be in order to recover the cores.