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Only huge catastrophic changes capable of altering the temperature of the whole body of the oceans can set a new global equilibrium in the short term (less than millennia). The sun can also do it gradually but it takes centuries e.g. from Roman Warm Period to Mediaeval Warm Period to Little Ice Age to now. The solar effect is heavily modulated over time by ocean cycles. A change in the composition of the air alone cannot do it.

...Oxygen isotopes are used as a palaeothermometer. Oxygen occurs in two forms, oxygen-16 and oxygen-18. These are incorporated into the calcite skeletons of marine creatures at different rates depending on the water temperature, more oxygen-18 at low temperatures, and more oxygen-16 at high. At the base of bed 25, the main mass extinction level, there was a sudden shift in the oxygen isotope ratios indicating a worldwide rise in temperature of 6 °C. This may not sound much, but it would have a profound effect on the world's ecology. Climatologists have been getting very excited recently about a half-a-degree rise in global temperatures.

The carbon isotopes suggest what might have caused the temperature increase. They show a massive shift towards the light isotope, carbon-12, exactly at the time of the big extinction. Pulses of carbon-12 in the geological record are usually indicative of a volcanic eruption or a large die-off (plants, animals and bacteria concentrate carbon-12 in their bodies and release it when they die). Both certainly happened at the end of the Permian. But the carbon-12 pulse is far too big to be explained by these mechanisms alone. Calculations of global carbon budgets have suggested that, even if every plant, animal, and microbe died and was buried, altogether they would only account for about one-fifth of the observed carbon shift. The Siberian Traps would have added another fifth. Where did the remaining three-fifths come from?

The extra carbon-12 was probably buried, frozen deep under the oceans in the form of gas hydrates. These are extraordinary accumulations of carbon-12-rich methane locked up in cages of ice at very high pressure. If the atmosphere and oceans warm up sufficiently, these gas reserves can suddenly melt and release their contents in a catastrophic way. The explosion of gas through the surface of the oceans has been termed a "methane burp". A very large methane burp at the end of the Permian could have produced enough carbon-12 to make up the deficit.

The cause of the burp was probably global warming triggered by huge releases of CO2 from the Siberian Traps. Methane is a greenhouse gas too, so a big burp raises global temperatures even further. Normally, long-term global processes act to bring greenhouse gas levels down. This kind of negative feedback keeps the Earth in equilibrium. But what happens if the release of methane is so huge and fast that normal feedback processes are overwhelmed? Then you have a "runaway greenhouse". This is a positive feedback system: excess carbon in the atmosphere causes warming, the warming triggers the release of more methane from gas hydrates, this in turn causes yet more warming, which leads to the release of more methane and so on. As temperatures rise, species start to go extinct. Plants and plankton die off and oxygen levels plummet. This is what seems to have happened 251 million years ago.

The narrative of Stephen Wilde makes a lot of claims about the role of air circulation and oceans. These claims are totally unsubstantiated

Q:
" The narrative of Stephen Wilde makes a lot of claims about the role of air circulation and oceans. These claims are totally unsubstantiated."

The problem is Q the very same is said about AGW, the REAL world does NOT work or respond like the prediction of your computer model and yet you continue as if it does. You quote from source references that support the views of AGW, Stephen on the other hand produces logical answers to changes we see for REAL not the changes in a test tube.

Venus has an extremely dense atmosphere, which consists mainly of carbon dioxide and a small amount of nitrogen. The atmospheric mass is 93 times that of Earth's atmosphere while the pressure at the planet's surface is about 92 times that at Earth's surface—a pressure equivalent to that at a depth of nearly 1 kilometer under Earth's oceans. The density at the surface is 65 kg/m³ (6.5% that of water). The CO2-rich atmosphere, along with thick clouds of sulfur dioxide, generates the strongest greenhouse effect in the solar system, creating surface temperatures of over 460 °C (860 °F).[27] This makes Venus's surface hotter than Mercury's which has a minimum surface temperature of -220 °C and maximum surface temperature of 420 °C, even though Venus is nearly twice Mercury's distance from the Sun and receives only 25% of Mercury's solar irradiance.

Venus is the case of a runaway greenhouse effect. The temperature and pressure of the atmosphere decrease with height, so water vapor rises in the atmosphere and encounters conditions that cause it to condense back into liquid water and fall back to the surface - a region called the "cold trap." On Earth, this is at a height of 9-15 km (5-9 miles) above the surface, but on Venus it lies at an altitude around 50 km (31 miles) due to the planet's closer proximity to the sun.

On Earth, the ozone layer is several kilometers above this, and the ozone prevents ultraviolet light from destroying water in our atmosphere. On Venus, there is no ozone layer, and the atmosphere doesn't become opaque to ultraviolet light until a depth is reached below the cold trap. This allows ultraviolet light to destroy water between this height and the cold trap's.

So, as water rises in Venus' atmosphere and reaches this region, dUV light dissociates it into two hydrogen atoms and one oxygen atom. The hydrogen is much lighter than the water molecule was, and so it easily escapes Venus' atmosphere. The water will usually quickly recombine with a carbon or carbon monoxide molecule to form carbon monoxide or carbon dioxide. This is probably one reason why there is so much carbon dioxide in Venus' atmosphere today.

Heavy water, however, which is composed of one oxygen, one hydrogen, and one deuterium (a proton and one neutron), cannot reach the requisite height as easily. If it does, it can still be dissociated just like normal water, but this happens at a much slower rate. Thus, a measurement of how much deuterium compared with how much hydrogen today shows that Venus has much more deuterium in its atmosphere for each hydrogen atom than Earth does. This is the strongest evidence that Venus has lost a massive amount of water in its history.

This process is a runaway one in that once less water is available to wash CO2 from the atmosphere, the CO2 level rises. This results in a stronger greenhouse effect, so the temperature rises. The higher temperature moves the cold trap higher, and the cycle continues at an accelerated rate because there is a larger region where water can become dissociated.

One cannot reproduce the Earth's climate in a laboratory.

There is no laboratory experiment that can encompass the full variability of climate.

The test of my description of the climate mechanisms can only be from real world observations.

Thus far it fits very well and if that continues for just a little longer then acceptance of my description will be inevitable.