> But there is new hope that deep cuts in emissions of greenhouse gases could stabilise rising temperatures.
How is this possible when you have water vapor in a positive feedback loop, which is a far more potent, prevalent ghg that increases with any rise in temperature.
"Water vapor reduction" has to be part of the message at this stage, not just carbon reduction.
Water vapour has a short residence time in the atmosphere, is self-limiting (excess water precipitates out as rain or snow), and is already at equilibrium given ambient conditions.
The one variable that could drive additional water vapour is CO2, which by warming the atmosphere further increases the ability to hold water, and the amount of water vapour present.
If you want to reduce water vapour as a greenhouse-gas component of the atmosphere, reduce CO2 levels.
Just to be clear water vapor capacity increases due to temperature, for example, relative humidity measures how much water vapor is in the air for a given temperature. Any sort of increase in temperature will increase water vapor.
Yes, CO2 raises the temperature, you get a massive increase in water vapor, which again, is a more potent ghg. Reversing that same amount of CO2 does not magically reverse all of that water vapor. This is the crux of the problem, why water vapor is now also a problem that needs to be addressed.
I don't really see how this is possible for humanity at a scale that affects global warming. Most water vapour by far is generated by nature itself. We couldn't make a dent in that.
The CO2 is what upset the balance and we are by far the biggest contributor there so it makes sense to address that.
The point is reversing the CO2 does not reverse all that proportionally much larger increase in water vapor... eg. we have no choice but to address water vapor as well as CO2 if we want to have any chance in fixing global warming.
It's both, actually. Water vapor is positive no matter what. Clouds can be both positive and negative at the same time, depending on cloud type, altitude etc.
This is one of the things that are hard to model. Get this wrong and you can swing from a mere +1 global warming (what CO2 alone would do in 100 years) to +3 or more.
How is this possible when you have water vapor in a positive feedback loop, which is a far more potent, prevalent ghg that increases with any rise in temperature.
"Water vapor reduction" has to be part of the message at this stage, not just carbon reduction.