Clouds remain a mystery unless you can prove CHANGES in cloudiness have caused CHANGES in the global average temperature. Clouds are too difficult to measure for an accurate global average, to discover small changes over time. Especially before the satellite age in the 1970s.
The IPCC generally ignores clouds, along with every other natural cause of climate change, since 1995. They HAVE to blame climate change on humans, after arbitrarily dismissing EVERY natural cause of climate change as "noise". There's 4.5 billion years of 100% natural climate change -- but never mind that. The IPCC was formed by the UN in 1988 to blame climate change on humans, so that's what they do. Never mind that real science does not START with the conclusion, as the IPCC did.
The 50% increase of CO2 from 1850 (estimate of 280ppm) to 2022 (measurements of 420ppm) should reduce Earth's ability to cool itself by a small amount.
That amount is impossible to determine because there are so many OTHER variables that can cause climate change (see list below) including changes in cloudiness. You would have to know the exact effects of ALL variables to know the exact effect of CO2. The answers are not known.
But we do know the global average temperature change in the past 120 years was small and could have 100% natural causes, or 100% man made causes, or some combination of both. The global warming since 1975 was faster than would be expected from 100% natural causes, meaning some man made causes are likely since 1975. That's not a precise answer, but climate science is not precise science. There are far more questions without answers, than questions with answers.
In fact, modern "climate change" is not science at all: It is always wrong wild guess predictions of a coming global warming crisis that never shows up. Predictions began in late 1950s science papers. So that's 65 years of wrong predictions.
A good theory about clouds that should make us love cloudy days:
As the planet gets warmer, oceans release some of their dissolved CO2 into the atmosphere with a lag of hundreds of years, according to Antarctica ice core studies. More CO2 in the atmosphere should inhibit Earth's ability to cool itself, making the troposphere warmer. A warmer troposphere will hold air more water vapor, the primary greenhouse gas. More water vapor should make the troposphere even warmer. So we have is a positive feedback to anything that causes more CO2 in the troposphere.
What I've just described is the water vapor positive feedback that Climate Alarmists claim will amplify the mild warming effect of CO2 alone, by 2x to 4x. That unproven theory creates a prediction of catastrophic man made global warming. An uncontrolled positive feedback would cause runaway global warming. That's what Climate Alarmists believe.
The obvious question is why there was never runaway warming in the apst 4.5 billion years. Our planet has had CO2 levels up to 10x higher than today. Today's CO2 level is relatively low compared with the prior 4/5 billion years, according to geologists. But there is no evidence of any runaway global warming in the past. Otherwise none of us would be alive today to debate climate change. We'd have a dead planet. So what happened?
One theory is that increased water vapor in the atmosphere caused more clouds to form, blocking more sunlight than before, and keeping the planet from overheating.
The iris hypothesis proposed by MIT climate scientist Richard Lindzen, Ph.D., et al. in 2001, suggested increased sea surface temperature in the tropics would result in reduced cirrus clouds and thus more infrared radiation leakage from Earth's atmosphere.
Without knowing why, we do know natural causes of climate change that warmed the oceans, which released dissolved CO2 onto the atmosphere, did NOT cause runaway global warming. Therefore, the water vapor positive feedback theory should not be expected to cause runaway global warming in the future.
In fact the history of climate predictions in the past 120 years strongly suggests that climate predictions should not be taken seriously. Even simple extrapolation of the climate in the past 50 years have not been useful as predictions for the next 50 years of climate. Climate predictions have been extremely inaccurate.
Which brings us back to what modern "climate change" has become: A 65 year series of always wrong, wild guess predictions of climate doom. Consistently WRONG predictions are not science. At the least, science requires consistently RIGHT predictions.
Here is my own list of climate variables. Man made CO2 is just one of many
- not the "control knob" of the global average temperature:
The following variables are known to influence Earth's climate:
1) Earth's orbital and orientation variations
2) Changes in ocean circulation,
ENSO and others
3) Solar Irradiance and activity
4) Volcanic aerosol emissions
5) Greenhouse gas emissions
6) Land use changes
(cities growing, crop irrigation, etc.)
7) Changes in clouds and water vapor
8) Random variations of a complex, non-linear system
9) Unknown causes of climate change
The variables above are not all independent.