All greenhouse gases are not equal


Head Honcho
Staff member

We sometimes mistakenly think greenhouse gases and carbon dioxide (CO2) are synonymous. After all, many climate change articles talk about CO2 induced global warming without mentioning any of the other contributors. But greenhouse gases encompass a wide range of components. At a high level, greenhouse gases divide into two broad categories: condensable and non-condensable components. Condensable gases are those whose concentrations are dependent on temperature.

The primary greenhouse gases are water vapor, carbon dioxide, methane, ozone, nitrous oxide, and chlorofluorocarbons. Water vapor is the only condensable gas in this group, and chlorofluorocarbons constitute the only purely human-made component. The distinction between condensable and non-condensable gases is important because non-condensable gases are the atmospheric components keeping our planet livable.

Water vapor differs from non-condensable greenhouse gases like carbon dioxide (CO2) or methane (CH4), whose concentrations hold relatively steady as temperatures change. These non-condensable greenhouse gases play a critical role in maintaining the earth’s surface temperature in a range that supports life as we know it. Without them, the earth’s average temperature would be about -18 degrees Celsius. A sheet of ice would cover the planet.
Earths average temperature used to be 33°C warmer, +15°C, than it would be without GHGs. It is now more than a degree warmer than that, rapidly closing on 2°C warmer.

If human activity had not increased the non-condensable gas concentrations by burning fossil fuels, today’s water vapor concentrations would be the same as before the industrial revolution. We don’t directly add more water vapor to the atmosphere. Instead, human activity adds more CO2, methane, nitrous oxide, and chlorofluorocarbons, causing temperatures to rise. Once the atmosphere is warmer, then it absorbs more water vapor.

Because water vapor is a condensable greenhouse gas, the maximum amount of moisture in a fixed volume of air relates directly to air temperature. Warmer air holds more moisture, hence more water vapor. But when air fully saturated with water vapor cools, the vapor condenses into a liquid. This condensation effect forms clouds and creates precipitation like rain and snow.
So CO2 is the driver, water vapor, increasing as the world warms. Water vapor is the positive feedback increasing the warming from CO2 and the other GHGs.

Cycles within cycles
The saying that every action creates an equal, but opposite reaction holds true for water vapor amplification. Additional water vapor leads to more clouds. Because clouds are fluffy and white on top, they reflect sunlight into space. Less sunlight then reaches the earth’s surface, so less solar heat is available for atmospheric warming. This process encourages cooling.

The dual heating and cooling roles of water vapor play out daily. Extra water vapor leads to increased heat retention, but it also creates more clouds to block sunlight and encourage cooling. However, the steady rise in average global surface temperatures over the past 100 years attests to a fact; warming is winning out over cooling in this battle.
Clouds are thought to generally increase warming over all. The types and heights of clouds are changing and this increases the warming of clouds over all. This is not well understood. Clouds forming at night trap IR below them, reflecting it back to the surface hence warming the surface. Driving through the midnorth of SA as I did last week in showery weather the car thermometre would drop by up to 2°C when clouds covered the local sky, rising again when the clouds moved away.

The real impact
Weather is one of the earth’s engines for heat dissipation, moving heat from hot areas to cooler areas, smoothing out large temperature variations. This process forms the global water cycle with heat evaporating water in some areas and precipitating this water over other regions. Since oceans cover 70 percent of the earth’s surface, evaporation from the oceans is a major part of the water cycle. A warmer atmosphere means more water evaporates from the oceans, and precipitation increases. These changes impact weather patterns worldwide.

Studies of ocean salinity, led by Lijing Cheng from the Institute of Atmospheric at the Chinese Academy of Sciences, tracked surface salinity changes over six decades. Their findings show how global warming amplifies the water cycle, creating a more dynamic range of environmental conditions—high salinity zones get saltier, and low salinity areas become even fresher.

The results are important because they indicate a future where dry regions become dryer and wet zones wetter. Extreme weather events will become more frequent, and large populations will grapple with regional shifts in water availability.

Dry seasons become longer and dryer, so the West Coast burns. Decreasing water flow in the Colorado River threatens 40 million people and billions of dollars in agriculture. More frequent hurricanes pound the USA’s Gulf and East Coast, submerging towns below ocean waters. Water vapor is the atmospheric link to these amplified weather patterns. It is also a greenhouse gas able to create its own positive feedback loop, further accelerating an already rapid rise in global temperatures.


Head Honcho
Staff member
It really is time to re-evaluate opposition to nuclear energy. This is mostly reflex not thought based. Small modular reactors sound good: quicker to build. Waste is not an insuperable problem and siting reactors out of reach of tsunamis on tectonically inactive land is just common sense and very possible here—we are not tiny Japan!

Fusion I think will be feasible at commercial (utility) scale within two decades. This is also nuclear energy and it would be a crying shame if irrational fears prevent its wide scale implementation. A multisource energy system, microgrids, more use of rooftop solar and wind with some nuclear for when renewables fall down: very cloudy, windless days.

Will rooftop solar and wind ever allow homes to be heated or cooled from rooftop energy sources? Certainly not yet—energy self-reliance is a myth, we do need utilities to provide supplemental energy. Increasing cloud cover will decrease power generated from rooftop solar. Supplemental electricity is needed even for residences—and we have not yet discussed the needs of industry! Nuclear will have to be in the mix or we will suffer from energy poverty as coal etc fired generators reach their end of economic life and are shut down.

SA can supply itself enough energy at low prices—in winter. In summer we pay through the nose for Eastern states coal fired electricity. Ideal situation for nuclear power.


Active member
Will rooftop solar and wind ever allow homes to be heated or cooled from rooftop energy sources? Certainly not yet—energy self-reliance is a myth, we do need utilities to provide supplemental energy.
The grid as a whole can't survive solely on solar and wind, but an individual can. My friend, Gary, built an energy efficient home, an energy efficient shop, and runs the pump for his in ground pool often. His total electric bill for the first year after solar panels was $67. That includes a $5/month hookup fee for using the grid as a storage medium by net metering. This eliminates the need and expense of batteries. His solar system supplements the grid during peak usage when the grid load is near capacity and he gets his energy from the grid at nighttime. His total expense for the solar panels and inverters was $13.5k. He says that the system will pay for itself in less than 3 years. He installed the system himself. We work in an electrical field and he also owns an air conditioning company and can get the latest and most efficient equipment.

We have had no problems with nuclear power here in Texas. The Comanche Peak Nuclear Power Plant is about 75 minutes from my house. It's well isolated and has a dedicated small lake to provide cooling water. They are heavily regulated. It's usually a good thing, but not always. I've never heard of any near misses or major accidents.

The one time I worked there, they would not let me bring my tools. Only their electricians were allowed to touch the equipment. The manufacturer called me in to smooth them over and fix the equipment when 2 of their 4 new units blew up and the Power Plant engineers were upset. I proved that their electricians blew up 2 new UPS systems because the electrician didn't understand DC electricity and polarity. The manufacturer was ecstatic when I told them that the problem was the customer's fault and that their equipment is working as it should.


Head Honcho
Staff member
Where my new block is I would prefer to be a bit self sufficient, battery as well as grid storage if I make that much power.

Solar panels on north facing roof of house and garage, even garden shed, wind generator(s) to recharge battery and, maybe, run the HWS at night. Or just run the HWS.

Friends living outside Bathurst in NSW had solar panels and a wood burning range for cooking and hot water. One electric fridge—a second fridge. propane. fridge was added later. Panels are more efficient nowadays and, I hope, cheaper. Rather more power should be possible. Dunno what I will do for heating—if I get my strawbale house an open fire should be enough. Mane some heating in the bedroom to kick on an hour before I arise from my slumbers. Power in Tassie is hydro so carbon neutral—I could do without solar and wind but for some self-reliance.

Will install at least one 10,000L rainwater tank, use greywater for the garden.