Month: January 2023

On Climate Change

January 10, 2023 — Leave a comment

Originally posted as a Facebook Note on June 20, 2017.

Neil deGrasse Tyson got into a pretty detailed discussion about climate change on a recent episode of StarTalk. Neil got input from a number of guests, including former NOAA administrator Kathy Sullivan, climate scientist Radley Horton, meteorologist Nick Gregory, paleoclimatologist Linda Sohl, and astrobiologist David Grinspoon (along with comedian Scott Adsit).

https://www.startalkradio.net/show/science-climate-weather-kathy-sullivan/?_sft_season=season-8

The entire episode is worth a listen, but Linda’s segment is especially relevant, starting at the 33:37 mark. These are some relevant points from that discussion:

  • Near the end of the most recent ice age (21,000 years ago), CO2 was around 180ppm. By natural processes over the 21,000 years prior to the end of the Industrial Revolution, CO2 levels rose from 180ppm to 285ppm in 1850.
  • Between 1850 and now, CO2 levels rose from 285ppm to 400ppm, and the rate is still increasing. “Human activity plus nature” did in 167 years what “nature alone” did in 21,000 years.
  • The last time CO2 levels were this high was during the Pliocene epoch (~3 million years ago). At that time, the global average temperature was ~2-3°C warmer than it is now, ice sheets on Greenland and Antarctica were much smaller, and sea levels were about 25 meters (~81 feet) higher.

Neil asked David Grinspoon about the risk of a runaway greenhouse effect on Earth similar to what we see on Venus. David said the best models indicate we’re not at risk of something that severe, but it’s not an experiment we should try, because “long before we got to a Venus-like state, it would be uninhabitable for us.”

How do we know what CO2 levels were before we started measuring them in our atmosphere? Bill Nye addressed that topic in his segment near the end of the episode, wherein he focused on how ice core samples are taken in places like Antarctica, Siberia, and Greenland. Scientists take samples of the atmosphere that are trapped in bubbles between the “arms” of snowflake crystals.

Further reading: https://www.nap.edu/read/13111/chapter/5