Guest “geological scale and context” by David Middleton,
2023 has been a hot year… We have the makings of a super-El Niño and an unprecedented injection of water vapor into the upper atmosphere stacked on top of a general warming trend since 1978, if not since the nadir of the Little Ice Age So, it should come as no surprise that we have seen satellite-era record high temperatures, this summer and early fall.
As a geologist, I always have to apply scale and context to everything.
Temperature anomaly records are great tools. They are the only way to accurately describe how global temperatures are changing over time. However, they lack scale. They lack a frame of reference.
It is a common adage that when a geologist takes a photograph of a person, that person is simply there for scale. Other scale references include: camera lens covers (rendered obsolete by smart phones), quarters, rock hammers, spouses and action figures (on April Fools Day only). The key is to come up with a reference that is relatable. And what temperature is more relatable than a thermometer?
Figure 1. UAH 6.0 from WoodForTrees (l), UAH 6.0 at gas station thermometer scale.
Here’s an enlarged version:
Tenths of a degree don’t really stand out on thermometers.
In geology, context refers to the setting. How do observations fit into the overall setting. Granite is a very common rock on Earth. If I find a football-sized (real football, not soccer) granite rock in Albuquerque, New Mexico, it wouldn’t deviate from the setting. If I found any sized granite rock on the Big Island (Hawaii), would instantly know that a smart-ass geologist intentionally put it there.
Irrespective of whether or not any of the recent warming has been caused by anthropogenic activities, it’s fairly easy to put that warming into context.
Terando et al., 2020, will help be demonstrate this. It features a variation of one of my favorite climate models.
Figure 3. Modeled human plus natural climate forcing compared to three instrumental records (see Terando for specifics)
Figure 4. Modeled human climate forcing compared to three instrumental records (see Terando for specifics)
If the models are reasonably accurate, the early 20th century warming can be explained by natural forcing mechanisms. Whereas, some or all of the warming since about 1975 cannot be explained by natural forcing mechanisms alone. That said, the models only incorporate known, reasonably well-understood, forcing mechanisms. Judith Curry illustrated this concept quite well…
Let’s assume arguendo that all of the warming since 1975 is due to anthropogenic greenhouse gas emissions. What would this mean? It’s about 0.8 °C. warmer now than it was in 1975 (the last time the models didn’t require an anthropogenic component). Here’s UAH 6.0 overlaid on the Terando, 2020 model:
Figure 6. Is +0.8 °C since 1975 a problem?
1974-1975: The Context
Figure 7. Time Magazine, June 24, 1974
Figure 8. Newsweek, April 20, 1975
Figure 9. Science News, March 1, 1975
Assuming the climate models are valid, fossil fuel emissions saved us from “The Ice Age Cometh.”
WTF do Hawaii, Albuquerque and granite have to do with this? Anyone?
Terando, A., Reidmiller, D., Hostetler, S.W., Littell, J.S., Beard, T.D., Jr., Weiskopf, S.R., Belnap, J., and Plumlee, G.S., 2020, Using information from global climate models to inform policymaking—The role of the U.S. Geological Survey: U.S. Geological Survey Open-File Report 2020–1058, 25 p.,