Tree Rings and Climate Change: Predictions and Warnings

One thousand years ago, what was the Earth’s weather like? The answer to that question is not as difficult as you might think. Older trees can provide an insight into this through their tree rings. Tree rings and climate change are directly related. Furthermore, scientists can now make predictions and offer warnings about our future through these same rings.¹ But, how?

In order to understand this, we require an understanding of what tree rings are and how they relate to climate change.

What are tree rings?

Within the inside of each tree, there are rings that provide an indication of the tree’s age and also the rough weather patterns it has been through over time. Each ring represents one year of the tree’s life over the four seasons. The characteristics of that ring – from its color and depth to its shape and size – provide scientists with an idea of the Earth’s weather patterns over the years.² ‌One interesting fact that tree rings show is that they are usually wider in warm and wet years, while they are thinner in cold and dry years. Conditions such as living through a drought might also be illustrated via tree rings, as there will be a visible lack of growth over a period of time.³

What can tree rings tell us about climate history?

Ancient trees can indicate the Earth’s weather in a specific region, going back thousands of years. The Bristlecone pine trees in California are thought to be almost 5,000 years old⁴, giving researchers a timeline of nearly 8,600 years of weather. The rings also have a timeline of weather going back nearly 12,500 years thanks to oak trees. ⁵

‌This information is useful in a variety of fields, such as archeology, weather prediction, and even history. Scientists have used ring patterns in building timbers to estimate their age. They can also learn when some buildings, like the Church of Nativity in Bethlehem, were constructed.⁶ Tree rings can also differ between species of trees, depending on how they react to different weather conditions. A single tree’s ring can only tell us the conditions it has lived under and its age. But, scientists can learn much more about past climates by studying large datasets of tree rings from particular areas.⁷ The study of climates of the past is known as paleoclimatology, and the science of tree rings is called dendrochronology.⁸ Tree rings are not the only insight scientists have into the past, but they are a reasonably reliable resource.

How can tree rings be used to forecast the weather?

‌Scientists can use tree rings to understand how the Earth’s climate was affected in the past. But, more importantly, the ability to read tree rings has also offered scientists help with forecasting weather in the future. As the New York Times put it, “this window into the deep climate past has become vital in a rapidly warming world, to show how the climate of the last half-century is far outside the historical norms going back thousands of years”.⁹

1. Nasa.gov. (2019). What Can Trees Tell Us About Climate Change? | NASA Climate Kids. [online] Available at: https://climatekids.nasa.gov/tree-rings/.
2. The Independent. (2019). What do tree rings tell us about climate change? [online] Available at: https://www.independent.co.uk/climate-change/news/climate-change-global-warming-tree-rings-earth-science-a8902576.html.
3. Nasa.gov. (2019). What Can Trees Tell Us About Climate Change? | NASA Climate Kids. [online] Available at: https://climatekids.nasa.gov/tree-rings/.
4. Encyclopedia Britannica. (n.d.). bristlecone pine | Facts, Oldest, & Lifespan. [online] Available at: https://www.britannica.com/plant/bristlecone-pine.
5. Environmentalscience.org. (2014). Environmental Science. [online] Available at: https://www.environmentalscience.org/dendrochronology-tree-rings-tell-us.
6. Bauer, B. (2018). How tree rings tell time and climate history | NOAA Climate.gov. [online] www.climate.gov. Available at: https://www.climate.gov/news-features/blogs/beyond-data/how-tree-rings-tell-time-and-climate-history.
7. www.usgs.gov. (n.d.). Tree Ring Science Offers Valuable Glimpse at Environmental Climate Trends. [online] Available at: https://www.usgs.gov/center-news/tree-ring-science-offers-valuable-glimpse-environmental-climate-trends [Accessed 15 Mar. 2021].
8. scied.ucar.edu. (n.d.). Tree Rings (Dendrochronology) | UCAR Center for Science Education. [online] Available at: https://scied.ucar.edu/learning-zone/how-climate-works/tree-rings.
9. Robbins, J. (2019). Chronicles of the Rings: What Trees Tell Us (Published 2019). The New York Times. [online] 30 Apr. Available at: https://www.nytimes.com/2019/04/30/science/tree-rings-climate.html [Accessed 2 Mar. 2021].