It's true, at least for today. Although the real concern in climate science is average concentrations of carbon dioxide over much longer periods of time, surpassing the 400 ppm mark, even for a day, is a historic milestone. 400 ppm was once a level we talked about avoiding altogether through mitigation of greenhouse gas emissions. Now, it's a reminder that we're not really doing anything to circumvent the steady increase in global carbon dioxide concentrations and global average temperature. Happy Friday!
One of the interesting things about the global carbon dioxide and climate systems is the concept of feedback loops. You already know that as atmospheric concentrations of carbon dioxide go up (and with them, the global average temperature) you get lots of different kinds of changes all over the place. For instance, mountain pine forests start experiencing warmer winters and smaller snowpacks. But, as those changes happen, they can actually trigger secondary effects that contribute to, and increase the rate of, climate change.
In this video, you'll learn about how warmer temperatures and lower snowpacks are contributing to the spread of massive pine beetle infestations across the western United States. This is more than just inconvenient. The pine beetles can quickly kill huge amounts of trees, raising the risk of property-destroying forest fires and razing whole ecosystems. And, as the trees die en masse, forests that were once carbon sinks (absorbing more carbon dioxide than they released) become emitters—adding more carbon dioxide to the atmosphere.