OpenChess

A professor of geological sciences at Ohio State and a researcher with the Byrd Polar Research Center, Thompson points to markers in numerous records suggesting that the climate was altered suddenly some 5,200 years ago with severe impacts.

Evidence shows that around 5,200 years ago, solar output first dropped precipitously and then surged over a short period. It is this huge solar energy oscillation that Thompson believes may have triggered the climate change he sees in all those records.

He points to perfectly preserved plants he discovered that recently emerged from the Quelccaya ice cap in the Peruvian Andes as that glacier retreats. This monstrous glacier, some 551 feet (168 meters) deep, has shown an exponentially increasing rate of retreat since his first observations in 1963.

The plants were carbon-dated to determine their age and tests indicated they had been buried by the ice for perhaps 5,200 years. That suggests that somehow, the climate had shifted suddenly and severely to capture the plants and preserve them until now.

In 1991, hikers found the preserved body of a man trapped in an Alpine glacier and freed as it retreated. Later tests showed that the human – dubbed Oetzi – became trapped and died around 5,200 years ago.

Lonnie Thompson
Professor Lonnie Thompson

Thompson points to a study of tree rings from Ireland and England that span a period of 7,000 years. The point in that record when the tree rings were narrowest – suggesting the driest period experienced by the trees – was approximately 5,200 years ago.

He points to ice core records showing the ratio of two oxygen isotopes retrieved from the ice fields atop Africa’s Mount Kilimanjaro. A proxy for atmospheric temperature at the time snow fell, the records are at their lowest 5,200 years before now.

He lists the shift by the Sahara Desert from a habitable region to a barren desert; major changes in plant pollen uncovered from lakebed cores in South America, and the record lowest levels of methane retrieved from ice cores from Greenland and Antarctica and all occurred at the same time – 5,200 years ago.

“Something happened back at this time and it was monumental,” Thompson said. “But it didn’t seem monumental to humans then because there were only approximately 250 million people occupying the planet, compared to the 6.4 billion we now have.

“The evidence clearly points back to this point in history and to some event that occurred. It also points to similar changes occurring in today’s climate as well,” he said.

“To me, these are things we really need to be concerned about.”

The impact of a climate change of that magnitude on a modern world would be tremendous, he said. Seventy percent of the population lives in the world’s tropics and major climate changes would directly impact most of them.

Thompson believes that the 5,200-year old event may have been caused by a dramatic fluctuation in solar energy reaching the earth. Scientists know that a historic global cooling called the Little Ice Age, from 1450 to 1850 A.D., coincided with two periods of decreased solar activity.

Evidence shows that around 5,200 years ago, solar output first dropped precipitously and then surged over a short period. It is this huge solar energy oscillation that Thompson believes may have triggered the climate change he sees in all those records.

“The climate system is remarkably sensitive to natural variability,” he said. “It’s likely that it is equally sensitive to effects brought on by human activity, changes like increased greenhouse gases, altered land-use policies and fossil-fuel dependence.

“Any prudent person would agree that we don’t yet understand the complexities with the climate system and, since we don’t, we should be extremely cautious in how much we ‘tweak’ the system,” he said.

“The evidence is clear that a major climate change is underway.”

Source: Ohio State University Research
Contact: Lonnie Thompson, (614) 292-6652;

thompson.3@osu.edu

Civilization in ice

One of the intriguing things about working in the tropics is that you’re often working where civilization started, Thompson points out. It seems that weather and climate have always been a topic of conversation since time immemorial.

“You can see some of the [climatic] events that are recorded in the hieroglyphics on the tombs of the pharaohs in the ice itself,” Thompson explains excitedly. “That’s really striking that you can actually do those things.”

For example, in ice recovered from the Himalayas at some 23,000 feet, scientists can see the telltale signs of a monster monsoon that killed 700,000 people in central India in 1790 from increased dust and enriched oxygen isotopes. By tracking powerful storms like these back through time, researchers can determine how often they naturally occur — and whether human-induced climate change may be fiddling with natural variability.

In several recent ice cores drilled to the bedrock from the Naimona'nyi ice field in the western Tibetan Himalayas at about 6,100 meters, a more sobering fingerprint of human civilization helps date the records — thermonuclear tests from the 1950s and 1960s, particularly the U.S. Castle Bravo test in 1954 on Bikini Atoll, Marshall Islands.

“Those become timelines because we know exactly when the tests took place. We find that you can determine the accumulation rate for this area since 1963 or 1951,” Thompson says. “We’ve done that across China.”

And what they’re finding from those radioactive layers is that there’s been little if any net accumulation in the last half-century. The 58 glaciers on Naimona'nyi once covered an area ten times greater than today.

Thompson has made 27 trips to the Qori Kalis Glacier on the Quelccaya Ice Cap.

“They’re very important for water supplies in these areas, and that’s especially true in the dry season,” Thompson says. “That’s true whether you’re looking at glaciers in the Himalayas or down through the Andes. There’s a very direct link to people, to hydroelectric power production, to irrigation, to municipal water supplies.”

Indeed, Thompson talks about people as much as he does the science behind his work. A favorite story seems to be about an expedition to Sajama, Bolivia. At the base of the mountain where the team hoped to drill into the glacier on the summit was a village, whose permission they needed before beginning their work.

Thompson made a four-hour presentation of what the scientists proposed to do and why. But the village medicine woman considered the idea a bad omen. “She was absolutely sure that drilling these glaciers was going to anger the gods,” Thompson says.

To appease the gods — and maintain good relations with the villagers, always a priority — Thompson agreed to donate $500 to the library and to hire local people for labor (already in the plan). Additionally, the ice core team participated in the sacrifice of an alpaca to ask forgiveness of the gods. In the end, the gods were happy, the villagers were happy, and Thompson got his ice cores.

“All of the projects have a story, the challenge of how you get into these areas and how you get the cores out,” he says. “And all of them have stories about how incredibly supportive people are, in places where you have only met them, and they want to help you with your job. Without them, we wouldn’t have accomplished any of this.

“At the end of the day, you’re a guest.”
The story continues

The next chapter in the story goes back to the beginning, to Peru and the Quelccaya ice field, when a team from Byrd Polar returns to the region this summer. Thompson and team have made several trips to the glacier in the last 35 years, like a doctor making repeated house calls to a sick patient. In this case, the fever is causing the 160-meter-deep ice cap to melt away.

In the wake of the glacier’s retreat in 2002, the researchers found a perfectly preserved wetland plant. Carbon dating tests indicated the plant had been buried in the ice for about 5,200 years. That suggests that the climate had shifted suddenly to capture the plant and preserve it without killing it.

The date is significant because other abrupt changes in climate from around the world — such as the shift of the Sahara from a habitable region to a barren desert — also occurred around the same time. Thompson doesn’t know what happened to cause a plant to freeze in time, but one hypothesis is that fluctuations in solar output may be to blame.

Evidence shows that about 5,200 years ago, solar energy from the sun dropped sharply and then surged over a short period. This huge flux may have triggered unusually strong winters in Peru that suddenly buried plants in snow and droughts that laid waste to the Sahara.

The mystery is on the top of Thompson’s scientific agenda, particularly if human-induced climate change is bringing us closer to some sort of similar tipping point. Figure out what happened five millennia ago, and you may have a crystal ball into the future.

But time is running out; the clues in the mystery are disappearing. By the end of the century, Thompson says, most of the world’s tropical and subtropical ice will vanish.

“It will be gone. And history will be gone,” he says.