Judge Gives Climate Homework To Parties Involved in Big Oil Litigation

Suggestions for the climate ‘red team’ response.

This post is motivated by a twitter thread from Andrew Dessler that responds to a recent ruling in the Northern California versus the oil companies lawsuit (discussed previously here)

The judge posed 8 science questions for each side to respond to. Dessler provided his answer to all 8 questions. My post focuses on question #8:

What are the main sources of heat that account for the incremental rise in temperature on Earth?

Dessler responded to the question in the following way:

JC’s response

There are many factors that contribute to changes in the Earth’s global average surface temperature.

Here are the global mean surface temperature anomalies since 1850. You see a substantial temperature rise from 1910 to 1940, a decline from 1940 to 1975, then a large increase from 1975 to 1998, a small increase from 1998 to 2014, then a recent spike in 2015/2016 associated with the super El Nino.

The IPCC AR5 (2013) concluded that:

“It is extremely likely that more than half of the observed increase in global average surface temperature from 1951 to 2010 was caused by [humans]. The best estimate of the human-induced contribution is similar to the observed warming over this period.”

Note: the analyses from climate models and ‘fingerprinting’ analysis point to ~100% attribution to human-caused warming since 1951.

The IPCC AR5 examined the radiative forcing from the period 1750 to 2010 (see Figure 6.3 above posted by Dessler).

Most of the radiative forcing is from CO2 over this period. However, fossil fuel emissions did not start increasing substantially until after 1950:

The observed warming prior to 1940, the slight decline of temperatures from 1940-1975, and the slowdown in warming from 1998-2014 obviously are not explained by fossil fuel emissions.

Read the entire post at Climate Etc