Archives par mot-clé : Water vapor

climate-debate

Are direct water vapor emissions endangering anyone?

by Real Climate, July 31, 2025

In the EPA EF reconsideration document there is a section on p62 where they attempt to make the argument that the CO2 endangerment finding would also apply to direct water vapor emissions to the atmosphere, which is (according to them) obviously absurd. But both claims are bogus.

First off, the definition of pollutant in the Clean Air Act (CAA) clearly does include CO2 as well as water vapor. This was the point litigated in Massachusetts v. EPA in 2007:

An air pollutant is defined as any substance, or combination of substances, including physical, chemical, biological, or radioactive matter, that is emitted into or otherwise enters the ambient air and may reasonably be anticipated to cause or contribute to air pollution.

A Hazardous Substance is further defined as one “that can cause or may reasonably be anticipated to cause adverse health or environmental effects“.

So there are two factors to assess. First, is the substance emitted into the air? (Yes, for both CO2 and water vapor). Second, might it be reasonably anticipated to cause adverse effects? (This is precisely the point of the Endangerment Finding process!). Thus it is not self-evidently absurd that water vapor emissions might be regulatable under the CAA, but the issue is whether there is any evidence that these emissions might plausibly have adverse effects.

It’s worth listing some pertinent comparisons between CO2, water vapor and a criteria pollutant like SO2 (which oxidises to SO4), to see the differences:

Substance CO2 SO4/SO2 Water Vapor (H2O)
Perturbation timescale(s) > 1,000 years ~ 2 weeks ~ 10 days
Increase over background since 19th Century (%) > 50% ~350% (Greenland, 1980) ~ 4% (since 1979)
~ 9% (estimate since 1900)
Anthropogenic direct emissions ~ 36 GtCO2/yr ~ 130 MtSO2/yr (1980) ~ 21 GtH2O/yr
Anthropogenic sources Fossil fuel combustion, deforestation Sulfur in coal, biomass burning Irrigation, combustion
Attribution of anthropogenic direct sources to atmospheric increase ~ 90% 100% ~4%
Impact of climate feedbacks ~ 10% (ocean/soils etc.) 0 % ~ 96% (impact of T on saturation vapor pressure)
Adverse effects of increase Increased heat waves, sea level rise, etc. Acid rain, public health, agricultural yield More intense rainfall, enhanced global warming

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climate-debate

Observed humidity trends in dry regions contradict climate models

by Simpson et al., Dec 26, 2023 in PNAS

Significance

Water vapor in the atmosphere is expected to rise with warming because a warmer atmosphere can hold more moisture. However, over the last four decades, near-surface water vapor has not increased over arid and semi-arid regions. This is contrary to all climate model simulations in which it rises at a rate close to theoretical expectations, even over dry regions. This may indicate a major model misrepresentation of hydroclimate-related processes; models increase water vapor to satisfy the increased atmospheric demand, while this has not happened in reality. Given close links between water vapor and wildfire, ecosystem functioning, and temperature extremes, this issue must be resolved in order to provide more reliable climate projections for arid and semi-arid regions of the world.

Abstract

Arid and semi-arid regions of the world are particularly vulnerable to greenhouse gas–driven hydroclimate change. Climate models are our primary tool for projecting the future hydroclimate that society in these regions must adapt to, but here, we present a concerning discrepancy between observed and model-based historical hydroclimate trends. Over the arid/semi-arid regions of the world, the predominant signal in all model simulations is an increase in atmospheric water vapor, on average, over the last four decades, in association with the increased water vapor–holding capacity of a warmer atmosphere. In observations, this increase in atmospheric water vapor has not happened, suggesting that the availability of moisture to satisfy the increased atmospheric demand is lower in reality than in models in arid/semi-arid regions. This discrepancy is most clear in locations that are arid/semi-arid year round, but it is also apparent in more humid regions during the most arid months of the year. It indicates a major gap in our understanding and modeling capabilities which could have severe implications for hydroclimate projections, including fire hazard, moving forward.
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Also here (NotricksZone)
unclassified

A Much Larger Greenhouse Effect – But Temperatures Dominated by Cooling

by W. Röst, Sep 9, 2022 in WUWT

Abstract

The Earth’s greenhouse effect is much larger than suggested so far. If surface radiation and the greenhouse effect set surface temperatures, our oceans would be boiling. Fortunately, they don’t. Water Earth has a strong water-vapor-based evaporative surface cooling mechanism that effectively sets and stabilizes surface temperatures at a much lower level than cooling by surface radiation emissions can do. Thanks to water vapor our temperature system is far more stable than admitted by the consensus, and thanks to water, water vapor, and clouds surface temperatures are favorable for present life.

Introduction

Early Earth consisted of hot molten lava covered by an extreme greenhouse atmosphere: hardly any surface radiation could reach space, if any. Nevertheless, its surface cooled. Upward convection brought sensible and latent heat from hot surfaces to elevations on the very edge of the atmosphere from where energy effectively could be radiated into space. Despite the near maximal greenhouse effect the surface of Early Earth cooled down and at a certain moment the first oceans developed. Those boiling oceans still resulted in a huge upward convective transport of energy, further cooling the surface. Until now, convective upward transport of energy plays the main role in surface cooling. Convection sets and regulates surface temperatures at actual level. Without evaporative-convective-cloud-cooling, our actual greenhouse atmosphere would theoretically result in a surface temperature of 202.3°C. On the real Earth the greenhouse effect warms the surface, but greenhouse warming does not set and control final surface temperatures. Earth’s H2O-based cooling system does.

Theoretical greenhouse effect

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Conclusions

The Earth’s greenhouse effect is huge, much higher than normally assumed. If cooled by ‘surface radiation only’ the surface of a theoretical planet would have had a surface temperature of 202.3°C. But the Earth’s surface temperatures are not set by the strength of Earth’s greenhouse effect. Additional H2O-based cooling systems keep the surface at a much lower temperature, balancing rising surface radiation uptake. At present, that balance is reached at a yearly average of 15 degrees Celsius.

Thanks to H2O-related surface cooling the Earth’s surface temperatures are bound to a narrow range, at a temperature level well suited for life on Earth. Due to its stability, life developed over many hundreds of millions of years.

Temperature regulates the cooling system; the cooling system regulates temperature.

climate and geology

Tonga Eruption Blasted Unprecedented Amount of Water Into Stratosphere

by C. Rotter, Aug 3, 2022 in WUWT

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This looping video shows an umbrella cloud generated by the underwater eruption of the Hunga Tonga-Hunga Ha’apai volcano on Jan. 15, 2022. The GOES-17 satellite captured the series of images that also show crescent-shaped shock waves and lightning strikes.
Credit: NASA Earth Observatory image by Joshua Stevens using GOES imagery courtesy of NOAA and NESDIS

The huge amount of water vapor hurled into the atmosphere, as detected by NASA’s Microwave Limb Sounder, could end up temporarily warming Earth’s surface.

When the Hunga Tonga-Hunga Ha’apai volcano erupted on Jan. 15, it sent a tsunami racing around the world and set off a sonic boom that circled the globe twice. The underwater eruption in the South Pacific Ocean also blasted an enormous plume of water vapor into Earth’s stratosphere – enough to fill more than 58,000 Olympic-size swimming pools. The sheer amount of water vapor could be enough to temporarily affect Earth’s global average temperature.

“We’ve never seen anything like it,” said Luis Millán, an atmospheric scientist at NASA’s Jet Propulsion Laboratory in Southern California. He led a new study examining the amount of water vapor that the Tonga volcano injected into the stratosphere, the layer of the atmosphere between about 8 and 33 miles (12 and 53 kilometers) above Earth’s surface.

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climate and geology, climate-debate

HOW THE EARTH BECAME A HOTHOUSE BY H2O

by Wim Röst, June 15, 2018 in WUWT

Water, H2O, determines the ‘General Background Temperature’ for the Earth, resulting in Hothouse and Ice House Climate States. During geological periods the movement of continents changes the position of
continents, oceans and seas. Because of the different configurations, a dominant warm or a dominant cold deep-water production configuration ‘sets’ average temperatures for the deep oceans. Changing vertical oceanic circulation changes surface temperatures, especially in the higher latitudes. During a Hot House State, higher temperatures in the high latitudes result in a high water-vapor concentration that prevents a rapid loss of thermal energy by the Earth.

These three processes, plate tectonics (continental drift), vertical oceanic circulation variability and variations in atmospheric water vapor concentration and distribution, caused previous Hot House and Warm House Climate States. A change in the working of those mechanisms resulted in a transition from the previous Hot House Climate State to the very cold ‘Ice House State’ that we live in now. That change was set in motion by the changing configuration of continents, oceans and seas.

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climate-debate

Does Global Warming increase total atmospheric water vapor (TPW)?

by Andy May, June 9, 2018 in WUWT

Some have speculated that the distribution of relative humidity would remain roughly constant as climate changes (Allen and Ingram 2002). Specific humidity can be thought of as “absolute” humidity or the total amount of water vapor in the atmosphere. We will call this amount “TPW” or total precipitable water with units of kg/m2. As temperatures rise, the Clausius-Clapeyron relationship states that the equilibrium vapor pressure above the oceans should increase and thus, if relative humidity stays the same, the total water vapor or specific humidity will increase. The precise relationship between specific humidity and temperature in the real world is unknown but is estimated to be between 0.6 to 18% (10-90%ile range) per degree Celsius from global climate model results (Allen and Ingram 2002) …

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