What is the relationship between global CO2 and temperature for the last 1,000 years?
After spending almost all of the last 800,000 recorded years as a climate amplifier1 (e.g., change in orbital cycles led to global temperature rise, releasing CO2 from the oceans, and the released CO2 led to an amplification of the warming), CO2 appears to have taken its place as a climate forcing since the industrial revolution. From ~1000 AD to the industrial revolution (late 1700s), CO2 levels were flat and temperatures slightly declined. Following the industrial revolution, CO2 levels rose rapidly and, with a climate lag2 of perhaps 40 years, temperatures have risen rapidly too. In fact, global temperature rise over the last 70 years (~1.4°C per century over the last 70 years; https://chartedterritory.us/2018/02/03/the-world-is-getting-enso-hot-el-nino-la-nina-and-rising-global-temperature/) has been about 20 times faster than coming out of the last ice age! With global atmospheric levels higher than any time since the Pliocene 3.6 million years ago when the world was ~8 °C warmer3, what does the future hold?
Methodology: CO2 data are taken from Scripps4. Global temperature data from 1000 to 1880 are taken from Marcott et al.5 and observed temperatures (1850 to 2017) from the Hadley Centre6. The two temperature datasets were “wiggle matched” for the years 1850–1880 by minor adjustment (-0.12 °C) of the Marcott et al. data. No Marcott data after 1880 are used or shown. The data were compiled and visualized using Microsoft Excel7.

  1. http://cdiac.ess-dive.lbl.gov/trends/co2/ice_core_co2.html
  2. https://www.skepticalscience.com/Climate-Change-The-40-Year-Delay-Between-Cause-and-Effect.html
  3. https://www.scientificamerican.com/article/ice-free-arctic-in-pliocene-last-time-co2-levels-above-400ppm/
  4. http://scrippsco2.ucsd.edu/data/atmospheric_co2/icecore_merged_products
  5. http://science.sciencemag.org/content/339/6124/1198
  6. https://crudata.uea.ac.uk/cru/data/temperature/
  7. https://products.office.com/en-us/excel