Happer is a climate scientist, despite the claims of his critics who are not scientists. His publishing history confirms that (see above).
There are many scientists who disagree with climate alarmism or the CO2 theory.
From above,
"Case in point is the peer-reviewed analysis completed in June, 2020 by eminent physicists William Happer and William van Wijngaarden. Mr. Happer is Professor Emeritus at Princeton University and van Wijngaarden is a professor in the Department of Physics and Astronomy at York University in Toronto, Both men are accomplished and renowned physicists with over 500 published papers to their credit. Mr. Happer is best known as the brilliant scientist whose insight into the physics of the atmosphere empowered the success of the Strategic Defense Initiative.
They applied highly detailed mathematical analytics to the physics of CO2 in the atmosphere and raised serious doubts about CO2’s ability to absorb heat after becoming “saturated” at current levels of 400 parts per million, and therefore unable to absorb significanty more heat from the Sun. Thus, any further increases in atmospheric CO2 – even doubling that amount to 800 parts per million – would only result in minimal increases in atmospheric temperature of 0.5C, or 1degree Fahrenheit.
This mathematically rigorous finding was validated through a controlled laboratory experiment conducted by a team of seven Viennese researchers in 2024. They measured the back infrared radiation of CO2 in a test chamber with increasing CO2 concentrations emulating realistic atmospheric conditions. They concluded that doubling CO2 from pre-industrial levels from 400 to 800 ppm “shows no measurable increase in infrared radiation absorption, and thus can lead to just 0.5C warming increase at most”.
This conclusion illustrates the reason why climate alarmists have never been able to explain the reason why the Earth has never experienced runaway warming in the past when CO2 levels were 5-10 times more concentrated than today, nor why the UN climate models based on linear warming theory have been proven to be so terribly wrong."