Past and Present Warming – A Temporal Resolution Issue
7 hours ago Guest Blogger 40 Comments
By Renee Hannon
This post examines how present global surface temperatures compare to the past 12,000 years during the Holocene interglacial. The AR6 IPCC climate assessment report, Climate Change 2021: The Physical Science Basis, by Working Group 1 states in their Summary for Policymakers section A.2.2:
“Global surface temperature has increased faster since 1970 than in any other 50-year period over at least the last 2000 years (high confidence). Temperatures during the most recent decade (2011–2020) exceed those of the most recent multi-century warm period, around 6500 years ago [0.2°C to 1°C relative to 1850–1900] (medium confidence). Prior to that, the next most recent warm period was about 125,000 years ago, when the multi-century temperature [0.5°C to 1.5°C relative to 1850–1900] overlaps the observations of the most recent decade (medium confidence).”
AR6
Paleoclimate proxy data records have low temporal resolution.
Comparing present instrumental data to the past is no small task. Temperature data during the Holocene and older are indirect measurements based on proxies. Scientists have compiled and extensively analyzed these proxy data covering the past 10,000 years. The datasets contain 100’s of records and include terrestrial, marine, lake, and glacial ice proxy data, to name a few.
Unfortunately, lake and marine proxy data are smoothed due to sediment mixing and uncertain age control. Smoothing of paleoclimate proxy data also occurs due to averaging of multiple data types together which destroys higher frequency decadal data (Kaufman and McKay, 2022). Hence, proxy data during the Holocene is multi-century at best, representing an average temperature smoothed over a couple hundred years.
https://wattsupwiththat.com/2023/03/29/past-and-present-warming-a-temporal-resolution-issue/
