Water Vapor Is the No. 1 Greenhouse Gas, So Why Don't the Climate Models Properly Account for It?
Judith Curry provides a forum at her Climate, Etc. site for climate science that doesn’t get enough attention. She currently has a study posted by Nobua Maeda, an Associate Professor of Civil and Environmental Engineering at the University of Alberta, Canada and Bruce Peachey, the President of New Paradigm Engineering in Alberta, up on her blog. Titled “Role of Humans in the Global Water Cycle and Impacts on Climate Change,” it is a very technical analysis but the fundamentals are easy to grasp.
Here are the key excerpts as I see it:
Recent climate change and increasingly scarce fresh water resources are two major environmental issues facing humanity. Water vapor is the most abundant greenhouse gas. Contemporary climate models only include the impact of water vapor as positive feedback on warming; the impact of direct anthropogenic emissions of water vapor has not been seriously considered…
Human activities indeed have been impacting climate but most of the key factors are related to water, as opposed to CO2. Atmospheric water vapor increase in the Northern Hemisphere has been by several percent per decade. In contrast, there has been little change in the Southern Hemisphere. Unlike water, CO2 is in a single phase and largely uniformly distributed in the atmosphere.
Thus, if CO2 were the cause of the current climate change, and if the ocean is the source of the water vapor that is supposed to increase by about 6 to 7% in response to every 1 °C of warming caused by the non-aqueous greenhouse gases, then the Southern Hemisphere should have observed more of the consequences than the Northern Hemisphere due to its much larger surface area of the oceans.
To the contrary, a 2% average increase in precipitation, that amounts to an average of about 2 Tt/year over the last century, has been observed in the Northern Hemisphere land precipitation, while no such increase was observed in the Southern Hemisphere land precipitation. This increase in the Northern Hemisphere land precipitation has been accompanied by an estimated 2 to 4% increase in the frequency of heavy precipitation events in the last 50 years, again in the Northern Hemisphere but not in the Southern Hemisphere.
Water is being consumed by humans at an increasing rate, predominantly in the Northern Hemisphere, at least by 3 to 4 Tt/year (excluding some sources such as reservoir evaporation). This increasing water consumption has been accompanied by reductions in the return flows of the fresh water to the oceans from the rivers in regions with intensive irrigation & industry, again predominantly in the Northern Hemisphere.
Other major contributors identified by the IPCC are water emissions and land use. Calls for the comprehensive integration of substantial changes in the hydrological cycle into global climate models are not new, but have received limited support, and consequently these causes have generally been ignored and not incorporated into the contemporary climate models to date.
Natural land water flux is based on water vapour coming on to land areas from the ocean, water falling as precipitation with some being re-evaporated from the landscape with the remaining flow, of about 40 Tt/yr, flowing back into the ocean to balance the flow of water vapour from the ocean. Ocean water vapor flux is 6 times larger than the land water vapor flux, even though the global water surface area is only about 3 times larger than the land area .
This is because: (1) the ocean surface is darker and hence absorbs more solar energy and (2) the ocean surface is always wet, which enhances mass transfer compared to the land surface, which sometimes is wet and sometimes is dry. At any one time, the atmosphere contains about 13 Tt of water, which contributes most of the greenhouse effect, and a given water molecule on average only spends about 10 days in the atmosphere each time it goes through the cycle…
Anthropogenic water emissions are large enough to result in a ~5 to 7% incremental increase (4 to 5 Tt/yr) in land-to-atmosphere water flux and a similar increase in water vapor in the atmosphere over land areas impacted by human water uses such as irrigation, evaporative cooling and evaporation from water reservoirs.
These water emissions are about 1000× the net increase in carbon mass emitted to the atmosphere and contribute significant amounts of latent energy to the atmosphere in cold northern areas, which GHG emissions do not.
We recommend that such direct anthropogenic emissions of water vapor should be coherently incorporated into the contemporary climate models before forcing extreme actions related to the carbon balance alone.
The above tells us two things. First, that climate models are horribly deficient, with so much being unknown and so little being properly studied if that’s even possible given the complexity and enormity of the task they are designed to perform. Secondly, it makes no sense to “force extreme actions” such as ludicrous EV mandates, subsidization of wholly uneconomic solar/wind projects and denial of critical fossil fuel infrastructure projects.
That’s precisely what our policy-makers are ordering us to do, of course, which tells us the whole ‘climate crisis’ isn’t about either but is, rather, about opportunities to grift off the ratepayers and taxpayers and accumulating power.
#Climate #WaterVapor #IPCC #Climate #ClimateModels #WaterEmissions
This is a fascinating post.
I'm not surprised it comes from Dr Curry's blog. She has spent a lot of time trying to figure out water. It is already fairly well know that water vapor can have a positive and negative effect on atmospheric warming depending on what level it is in the atmosphere and how much of it there is. The fact that humans may be directly altering the water cycle to such a degree was not something I was aware of. It makes a lot of sense that this would have an impact on the climate
The most significant GHG in our terrestrial atmosphere is also the least studied. Water vapor and clouds have radically different effects on ground temperatures and are not well enough understood so are ignored by modelers.