A thousand miles to the East of the Kauwerak's home a scientist is pulling out a core from an ancient tree and looking for a centuries-old weather report.
Just across the border between Alaska and the Yukon Territory Gordon Jacoby is kneeling in front of a white spruce tree. This dirt-stained man is a leading dendrochronologist. He studies climate change by counting and measuring tree rings. Jacoby pulls a hollow steel augur from a holster and attaches a cross bar. He grasps the bar's two handles, places the auger's tip against tree and leans forward.
Getting started is the hardest part. The teeth bite in after a few turns. Then you don't have to push anymore.
Jacoby slowly rotates the corer, driving it deep into the trunk. The scientist has sampled trees like this throughout the arctic. At high elevations and high latitudes trees act like thermometers. Barely able to survive in these harsh habitats, trees respond dramatically to minute temperature shifts.
When the auger reaches the center of the tree, Jacoby reverses the process and removes the tool from the wood. From the black corer, he pulls out a pale yellow soda straw-shaped cylinder of wood.
This tree is a beauty. This is almost 300 years old. I'll core this again because I missed the center badly. This one I got the pith of the tree. See the bull's eye by my thumbnail. That's what you aim for.
Each ring represents a year's growth. In this climate, thick rings mean a good or a relatively warm year; thin rings mean poor, frigid weather. By counting rings, Jacoby charts temperatures for hundreds of years back into history. Jacoby pulls out another butter-colored core.
Jacoby says the arctic climate is representative of earth's overall temperature. Which means his tree-ring measurements could show global trends. It's a view not shared by all climate researchers, but one with much evidence to support it.
See the juvenile growth when the tree is just getting started?, Jacoby asks, motioning to the rings. In fact… you can see the fine rings for a long time. And here we are entering the 1920s or 1930s when global warming took effect. You can see these wider rings all the way out to the bark. This is evidence that you have indeed had a climate change. It is showing you that as a mature tree it is doing much better.
The thickness of a tree ring gives annual average temperature. But dendrochronologists can squeeze out even more information from the thin pencils of wood they remove from trees like the one Jacoby has cored. They can determine whether a summer was cool or warm. They do this by gauging how well the tree was growing during the summer, when the outermost portion, or latewood of a ring is put on. In arctic climates, warm summers produce wood that is more dense, like lead; cold summers cause wood that is less dense, like Styrofoam. Not long ago Jacoby published an unusual scientific paper about research using this technique. The project began with a colleague's off-hand remark about legends of Alaska's native Inuit people. From his tree ring studies, he knew of an abnormally frigid summer. The year 1783.
[My colleague] once said to me there is an Inuit oral tradition written down that describes an event several centuries ago where almost everybody died because of a really cold summer. And I knew this year 1783 because we'd worked on it also. Some earlier dendrochronologists had noted this was a very unusual ring in the Alaska -- northern Alaska -- series. They just noticed it visibly, whereas we actually [had] done what they call density measurements of this particular ring. [We] found that it was unique in the last 400 or 500 years. … this latewood density is very light when there is a cold summer. My first thought was, this has to be the same year that it was super cold there because according to the Inuit oral tradition, this disaster was unique in their record.
Seeking confirmation, Jacoby scrutinized the written legend. He reexamined wood samples and he searched the records of the first white visitors to Northwest Alaska, Russian and European explorers.
They came here in the 1770s and made certain notes about villages and things. They came here -- to Alaska -- in the 1790s and noticed a decrease in the population. And said there seem to be fewer people than there were. And certain other anthropologists who've delved into early histories have heard tales of famine around this time too. So it all fit together that 1783, the trees recorded a temperature change, there was a legend of a lot of people dying because of no summer around that year and the observations of the Russian explorers that there was a decrease in population.
Some anthropologists are skeptical that the year of no summer legend could have occurred in 1783. If it had, they say the region would have been nearly empty when explorers went through in the mid 1800s. It wasn't. Jacoby says this inconsistency could be explained away. For instance, perhaps natives from elsewhere moved in after the weather-induced famine. He insists the theory is viable.