Earth’s atmosphere is made up of many different kinds of gas, most are naturally occurring, some are added unnaturally. Some are considered greenhouse gasses, some are not. In this post I will break down the chemical make-up of the atmosphere that surrounds our globe and explain what effect some of these gasses have on temperatures and our weather.
Earth’s Gases
To put the various gases that surround our globe in perspective, Earth’s atmosphere is made up of approximately 78 percent Nitrogen, 21 percent Oxygen, and a little less than 1 percent Argon. None of these are greenhouse gasses and have no direct physical influence on the temperature at the Earth’s surface.
The remainder of the atmosphere is made up of trace amounts of other gases. Several of those trace gases are greenhouse gases, gases that can trap heat. The main ones are Carbon Dioxide (CO2) and Methane (CH4). CO2 makes up around 0.042 percent of the atmosphere and CH4 accounts for 0.00017 percent. Those are small portions compared to the most abundant greenhouse gas in the atmosphere, which is Water Vapor (H20).
Water Vapor is a variable gas. It’s portion of the total make-up of the atmosphere accounts for between 0.4 percent over very dry areas, like the deserts, to around 4 percent over tropical locales. Water Vapor also accounts for 95 percent of all the greenhouse gases in the atmosphere, making it the largest and most dominant greenhouse gas in our atmosphere.
CO2 vs. H20
Carbon Dioxide has received an unfair reputation for being the main temperature control knob on the planet, whereas it is a small piece of a larger puzzle. CO2 does play an important role in helping to balance temperatures at the Earth’s surface, without CO2 the planet would become uninhabitable.
Approximately 97 percent of the total amount of CO2 in the atmosphere comes from natural sources, mainly from the oceans. Only around 3 percent of the total CO2 comes from unnatural sources. So, the human contribution of C02 to the total amount of C02 currently stands at 0.00126 percent.
C02 that is emitted into the atmosphere does hang around for long periods of time, from both natural and unnatural sources. Luckily, the majority of that gets balanced by CO2 that is absorbed, by plants, oceans, etc.
(Side Note: Learn more about CO2 in an article I wrote in the Jackson Hole News & Guide in May 2022: How much do you know about Carbon Dioxide?)
Compared to CO2, Water Vapor (H2O) is a much more influential greenhouse gas when it comes to controlling temperatures and weather patterns around the globe. It is also unique in that it can present itself in three different forms: as a gas, a liquid, or a solid. That is, as water vapor, water droplets, or ice crystals.
In the lower levels of the atmosphere, Water Vapor that condenses into water droplets to form clouds becomes our daily thermostat. In the upper levels of the atmosphere Water Vapor in its gaseous form is also capable of regulating temperatures at the Earth’s surface. Let me explain in more detail, as Earth’s heating and cooling system is rather complex.
To compare the power of both gases and their effectiveness as a greenhouse gas, here is what science tells us:
According to NASA’s Earth Observatory, “Because scientists know which wavelengths of energy each greenhouse gas absorbs, and the concentration of the gases in the atmosphere, they can calculate how much each gas contributes to warming the planet. Carbon Dioxide causes about 20 percent of Earth’s greenhouse effect; water vapor accounts for about 50 percent; and clouds account for 25 percent. The rest is caused by small particles or aerosols, and minor greenhouse gases like methane”.
Therefore, H2O accounts for 75 percent of all the warming, making it the undisputed controller of the Earth’s Thermostat!
H2O as the Thermo-regulator
In the lower levels of the atmosphere, when there is less H20 over us, there is less cloud cover. Clear skies during the day allows more shortwave radiation from the sun to reach the Earth’s surface, producing warmer daytime temperatures. The opposite is true at night, clear skies allow more long-wave radiation to escape to space, resulting in cooler overnight temperatures.
When there is more H20 over us, there is more cloud cover. During the day, clouds impede solar radiation from making it to the Earth’s surface, resulting in cooler daytime temperatures. At night, the outgoing long-wave radiation is blocked as it tries to escape to space and — like throwing an extra blanket on your bed at night — the result is warmer overnight temperatures. Most of us knew all that intuitively.
In the upper levels of the atmosphere, where Water Vapor primarily exists in its invisible, gaseous phase, the effects can be even longer lasting than the daily coming and going of clouds that we see in the lower levels of the atmosphere. Making Earth’s heating and cooling system even more complex.
What you may not know, is that in the upper levels of the atmosphere, Water Vapor is a very effective greenhouse contributor. Up there, it primarily exists in its invisible, gaseous phase, or presents as high, thin cirrus clouds made up of tiny ice crystals.
Water Vapor in the very upper levels of the atmosphere allows incoming solar radiation to penetrate through, but it inhibits long-wave radiation from escaping out to space overnight. Under that scenario, daytime highs and overnight lows will be warmer at the Earth’s surface.
The whole picture, as I mentioned is way more complex and kind of looks like this:
One way that humans add more Water Vapor to the upper levels of the atmosphere is from jet exhaust. Those contrails (condensation trails) that you see on certain clear, blue-sky days are from the warm exhaust hitting very cold air and forming ice crystals, which sometimes spread out into a thin cirrus-type cloud cover at 35,000 to 40,000 feet.
Increasing the amount of water vapor in the upper levels of the atmosphere will result in warmer temperatures at the Earth’s surface. Which can also happen naturally. And it did, very recently.
Eruptive Gases
Not much was said initially about the Hunga Tonga-Hunga Ha’apai volcanic eruption that occurred in the South Pacific, near the island of Tonga, on January 15th, 2022. But now we are starting to see the effect it has had on temperatures and the disruption of weather patterns around the globe.
Hunga Tonga was a rare, and extremely large underwater volcanic eruption. Thought to be the largest such underwater volcanic eruption in recorded history. When an undersea volcano erupts it sends more water into the atmosphere, rather than Sulfur Dioxide, like above ground Volcanoes do. It has been estimated that Hunga Tonga injected 3 billion tons of Water Vapor into the sky, all the way up into the stratosphere.
It has also been estimated that this single eruption increased the amount of Water Vapor in the stratosphere by 10 percent. And slowly over the last few years that Water Vapor has been circulating and spreading around the globe.
Watch the videos from the GOES Satellites (Band 9: mid-level water vapor) at the time of the eruption. The reach of Hunga Tonga’s shockwave is impressive!
Click here: Hunga Tonga Eruption Satellite Water Vapor Images
Undersea vs. Above Ground Eruptions
The effect on temperatures and the weather around the globe from an undersea volcanic eruption vs. an above ground eruption are quite different, because of the type of gas each one spews into the atmosphere.
One of the largest above ground volcanic eruptions in history was Mt. Pinatubo, which violently erupted in the Philippines on June 13th, 1991. It was the second largest volcanic eruption in the 20th Century. Second only to the Novarupta eruption on the Alaskan Peninsula in June of 1912, in what is now part of Katmai National Park.
These types of volcanic eruptions put copious amounts of fine ash particles and various other gases high into the atmosphere, some reaching all the way to the stratosphere. Sulphur Dioxide (SO2) being the dominant gas from this type of eruption. Sulfur Dioxide when combined with water or water vapor converts into Sulfuric Acid, which then forms fine sulfate aerosols. Those aerosols increase the reflection of incoming solar radiation, thus cooling temperatures at the Earth’s surface.
As the ash and gas cloud spreads out and circulates around the globe, this cooling effect can cover a good portion of the globe and linger for several years. Which it did, and it shows in our local climate records. For instance, the Summer of 1993 was the coldest and wettest summer ever recorded in Jackson Hole.
The difference between Hunga Tonga’s eruption and above ground volcanic eruptions like Pinatubo is that undersea volcanic eruptions spew less Sulfur Dioxide into the atmosphere, most of it dissolves in the ocean. It was estimated that Hunga Tonga only spewed about 440,000 tons of SO2 into the atmosphere, versus the 17 megatons from Pinatubo. Negating any significant cooling effect for most of the Planet from the Hunga Tonga eruption.
Final Thoughts
Because you now know that Water Vapor is the most prevalent greenhouse gas in the atmosphere, and that greenhouse gases trap heat, you don’t need to be a rocket scientist to figure out the result should be warmer temperatures.
According to a statement put out by NASA back in August of 2022 about the effects of Hunga Tonga, “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.” And the effects are estimated to last for up to 5 years or longer. Which means we have a least a couple more years to go until all that extra water vapor finally dissipates.
That may explain some of the unusual warmth, and the unusual weather patterns, that we’ve seen around the globe the last couple of years. So, we may have a couple more years to go until that extra water vapor finally dissipates.
Hopefully, if nothing else, this little science lesson has taught you which gas really has control of Earth’s Thermostat.
Post by: meteorologist Jim Woodmencey