Researchers use things like tree rings and ancient ice cores to glean information about the planet’s temperatures. Photos: Unsplash//Wikimedia Commons
Yesterday, as I was sitting with my fiancé on the porch, I checked our thermostat. It was 30-ish degrees C (about 88 F), which is a little hotter than usual for where we live. It’s not all that strange to hit temps like that on Vancouver Island in the summer, but we’ve had a stretch of it for a while now. And that’s strange. The sky is often hazy with wildfire smoke and people around the world are dealing with record-breaking temperatures. I mentioned that it had just been announced that June was the hottest month on record. “But how do scientists know the world temperatures going back that far?” my fiancé asked. I had a vague answer — ice cores, tree rings, etcetera — but nothing that actually answered her question. So I thought I’d try and figure it out.
As it turns out, ice cores and tree rings are indeed very useful. “Ice cores are scientists’ best source for historical climate data,” NASA wrote. “Every winter, some snow coating Arctic and Antarctic ice sheets is left behind and compressed into a layer of ice. By extracting cylinders of ice from sheets thousands of meters thick, scientists can analyze dust, ash, pollen and bubbles of atmospheric gas trapped inside.”
According to NASA, the deepest ice cores we’ve pulled up are around 800,000 years old. Little bits of dust, ash, and other ancient detritus are trapped in the ice then frozen over, where they sit waiting to tell us the secrets of the past. Those particles give researchers clues about volcanic eruptions and forest fires, while certain ions can give hints about ocean activity, sea ice levels, and even the sun’s intensity. Trapped bubbles can be released to give a tiny examples of the Earth’s atmosphere through the ages, too, including those ever-rising greenhouse gas levels.
Tree rings can be useful, too, as strange as it sounds. While it’s generally known that a tree gains a ring approximately every year, those rings speak volumes. NASA says they “keep a rough record of each growing season’s temperature, moisture and cloudiness going back about 2,000 years.”
That’s not all, though. Corals whisper secrets of the past, too, if we just learn how to listen. Like trees, corals have growth rings that tell us a lot about temperature levels of ancient oceans, as well as what kinds of nutrients were available and at what levels. Researchers also pull up benthic cores, which come from the ocean floor. Like other land-based corers, sediment corers cut deep into the ocean floor and pull up a tube full of sediment. Often, caps are automatically employed to seal off the core at either end, protecting the samples within from contamination from today’s world.
“With benthic corers, scientists obtain samples containing organisms (including the very small ones, microbes) found in the benthos, as they are found naturally,” explained scientists from the Census of Marine Life. “Scientists can then identify what species are in the sediment as well as how abundant they are. Other information can also be gained, such as how and at what level organisms live and move in the sediment.”
As our world changes, it’s becoming increasingly important to learn as much about the past as we can in an effort to see where we went wrong and how we can fix it.
