Well, jopo, it sure looks like they know very well, as far as predicting global temperature changes goes.
These models include estimates of water vapour feedback. And it looks like they have it right.
So it seems you aren't raising a significant issue affecting our ability to predict temperature rises so far.
So what is it you are beating up here?
Here's your reference, below. As you said, a quick google finds it. It is clear, as they say, that "the basics of the hydrological cycle are fairly well understood".
And that is clearly a good enough understanding to model global temperature changes accurately, as above.
As they discuss, what they are after is more detail to help them to better determine possible cloud feedback effects, and possibly other factors. There is plenty of study on clouds and uncertainty. And none of those suggest cloud formation saves us from warming. So sure, better knowledge on this will help. But it's clearly not stopping good global temp forecasts. And other studies on clouds don't suggest this is going to avoid the impacts we face.
In fact, quite possibly the opposite. Increasing CO2 might lead to dramatic cloud loss and increased warming.
https://www.nature.com/articles/d41586-019-00685-xhttps://www.newscientist.com/article/2209661-climate-change-may-thin-high-altitude-clouds-and-trigger-more-warming/But now, ahead of those sort of impacts, there is some evidence of mitigation from clouds. See the link below. That benefit is clearly being picked up by global model assumptions, given they are predicting global temperature changes well.
https://www.sciencedaily.com/releases/2019/03/190325120401.htmSo it seems that cloud benefits are already being modelled, but risks exist of a break down in clouds and increased future warming as a result. It's considered another tipping point risk.
We're seeing another jopo storm in a tea cup. All sound and fury signifying .... nothing much. Except the possibility of greater risks than we currently allow for.
https://www.ncdc.noaa.gov/monitoring-references/faq/greenhouse-gases.php?section=watervapor"
Water Vapor is the most abundant greenhouse gas in the atmosphere, which is why it is addressed here first. However, changes in its concentration is also considered to be a result of climate feedbacks related to the warming of the atmosphere rather than a direct result of industrialization. The feedback loop in which water is involved is critically important to projecting future climate change, but as yet is still fairly poorly measured and understood.As the temperature of the atmosphere rises, more water is evaporated from ground storage (rivers, oceans, reservoirs, soil). Because the air is warmer, the absolute humidity can be higher (in essence, the air is able to 'hold' more water when it's warmer), leading to more water vapor in the atmosphere. As a greenhouse gas, the higher concentration of water vapor is then able to absorb more thermal IR energy radiated from the Earth, thus further warming the atmosphere. The warmer atmosphere can then hold more water vapor and so on and so on. This is referred to as a 'positive feedback loop'. However, huge scientific uncertainty exists in defining the extent and importance of this feedback loop. As water vapor increases in the atmosphere, more of it will eventually also condense into clouds, which are more able to reflect incoming solar radiation (thus allowing less energy to reach the Earth's surface and heat it up). The future monitoring of atmospheric processes involving water vapor will be critical to fully understand the feedbacks in the climate system leading to global climate change. As yet, though
the basics of the hydrological cycle are fairly well understood, we have very little comprehension of the complexity of the feedback loops. Also, while we have good atmospheric measurements of other key greenhouse gases such as carbon dioxide and methane, we have poor measurements of global water vapor, so it is not certain by how much atmospheric concentrations have risen in recent decades or centuries, though satellite measurements, combined with balloon data and some in-situ ground measurements indicate generally positive trends in global water vapor.
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