A new study uses existing temperature and CO2 records and albedo/natural variability attribution to suggest most of the recent warming is natural. The climate sensitivity to CO2 forcing is just over 0.2°C for a 100 ppm concentration increase.
Dr. Syun-Ichi Akasofu is an “expert in aurora physics, solar physics, geophysics, and magnetosphere” and the founder of the International Arctic Research Center at the University of Alaska, Fairbanks.
He and a co-author suggest albedo changes and multi-decadal oscillations (natural variability) explain about 0.4°C of the 0.5°C warming that occurred from 1975-2000. The rate of global warming has not risen linearly in concert with human greenhouse gas emissions, but instead it has oscillated from -0.005°C per year to about +0.018°C per year for the last 150 years. This weak to non-existent correlation between CO2 and temperature further disconfirms the assumption greenhouse gases are primarily driving global temperature trends.
Image Source: Akasofu and Tanaka, 2021
As suggested, greenhouse gases are only responsible for “about 0.1°C, instead of 0.5°C” of the last quarter of the 20th century’s warming, as “the effects of the greenhouse gases are only one fifth of the IPCC assumption on the basis of the observed CO2“.
The temperature rise between 2000 to 2018 “is at most 0.1°C” even though CO2 rose by nearly 40 ppm during these 19 years. Climate models suggest it should have warmed 0.4°C or more from 2000 to 2018 due to the climate’s presumed strong sensitivity to greenhouse gases.
On the basis of the 0.1°C warming from CO2 from 1975 (331 ppm) to 2000 (370 ppm) and the necessarily less than 0.1°C warming from CO2 during the 2000 (370 ppm) to 2018 (408 ppm) period, Akasofu and Tanaka assert the climate’s sensitivity to CO2 rise may be “a little more than 0.2°C” per 100 ppm. This suggests doubling CO2 from pre-industrial levels (280 ppm to 560 ppm) produces just a 0.6°C increase in surface temperature.
A 0.6°C per 280 ppm CO2 climate sensitivity is hardly cause for alarm.