Global Warming - does water vapor do more harm than CO2?

Question

I saw a video saying that water vapor accounts for 95% of greenhouse gas (with CO2 accounting for a small percentage), thus actually causing more harm to the environment than CO2--is this true? I trying to understand the whole Global Warming issue, but I'm getting conflicting information. Help please.

Answer 1

Hmm..-interesting way to look at it. Of COURSE moisture in the air DOES affect things...-causes cars to rust, mildew to form, glass to fog over, -stuff like THAT. But that's a "Natural" phenomenon- & it doesn't actually poison or harm anything. The excess CO2 we're dumping into our Environment- IS upsetting the "balance" of greenhouse gases in our Atmoshere- so that they're trapping More & MORE solar radiation near the ground, resulting in Global Warming. In FACT (now that I think of it), increasing CO2 levels- will result in MORE water vapor (aka- "humidity") & thus more fuel for big storms & hurricanes!!! So don't be fooled; CO2 is the culprit we're dealing with- and what we need to DO something about...

Answer 2

yes water vapor is a greenhouse gas. but in clouds it reflects the suns energy back into space cooling earth. GO H

Answer 3

That's correct. CO2 is a minor greenhouse and humans generate only a few percent of the CO2 that exists naturally. Carbon dioxide is not a pollutant, in fact without CO2 all plant life would die and the animals that eat plants would die too.

Answer 4

Anything which blocks sunlight does harm and add to global warming for heat is entrapped and cannot escape from the Earth.

Answer 5

SUMMARY ANSWER

Yes there's lots of water vapour in the atmosphere, unlike the other greenhouse gases it's levels are constant and it's essential to the natural balance of our atmosphere.  We can't increase levels of water vapour and it can't contribute to anything other than the natural greenhouse effect.

MORE DETAILED ANSWER

Good answers above from Ecolink and Bob.  I'll try to add a little more and explain something of the science behind it.

Water vapour accounts for more than 99% of all the greenhouse gases (GHGs) but compared to the other GHGs it's weak and ineffective.  We measure the effectiveness of GHG's using something called Global Warming Potential (GWP) .  GWP takes carbon dioxide as having a value of 1, if for example, something had a GWP of 10 it means it's 10 times as effective at retaining heat.  

The (100 year) GWPs of the five main greenhouse gases (by contribution to GW) are...

Water vapour - <0.01

Carbon dioxide - 1

Methane - 23

Nitrous Oxide - 296

Dichlorodifluoromethane - 8500

Another important thing to take into account is how long these gases remain in the atmosphere.  Water vapour forms part of a natural water cycle and has an atmospheric lifetime of about 4 days, carbon dioxide is about 115 years and dichlorodifluoromethane is forever.

Further, water vapour forms part of a natural cycle and when there's too much of it in the atmosphere (saturation point) it falls back to earth as precipitation.  If humans were to somehow produce vast quantities of water vapour all that would happen is that it would rain.  At any one time about 1% of the global atmosphere is water vapour but due to the physical properies of our atmosphere it can be as much as 4% in very warm conditions and 0% in very cold conditions (the warmer air is the more moisture it can contain).

What we need to remember is that water vapour exists in much greater quantities than the other GHG's and whilst it's not good at retaining heat the fact that there's so much of it means it contributes up to a maximum of 72% of global warming.  This doesn't mean that 72% of the current warming is due to water vapour as there's been no change in levels of water vapour, it means that up to 72% of the overall GW is caused by water vapour.  Just as well really because without the natural greenhouse effect our planet would be too cold to support life.

Answer 6

Ahhh. I had the same confusion as you. That is...until I read this:

USATODAY.com

http://www.usatoday.com/weather/climate/...

We have little to none (I think none) control over water vapor.

"But, if the atmosphere warms with added carbon dioxide, this can increase the amount of water vapor in the air because more water vapor can evaporate into warm air than into cold air."

--From the link I provided. =)

Answer 7

Water vapor is the most important greenhouse gas.  But nature can control it, and regulate the warming effect.

Nature tries to control CO2 also.  But we're digging up carbon the natural cycle buried bit by bit, and burning it real fast.  That upsets the natural balance of CO2.

Look at this graph.

http://scrippsco2.ucsd.edu/graphics_gall...

The little squiggles are nature doing its' thing. CO2 falls a bit during summer when plants are active, and rises during the winter. The huge increase is us, burning fossil fuels (in addition to the shape of the graph, the increase numerically matches the increase in fossil fuel use). The scientists can actually show that the increased CO2 in the air comes from burning fossil fuels by using "isotopic ratios" to identify that CO2.  

Man is upsetting the balance of nature.  We need to fix that.

Answer 8

Yes, water vapor is a serious greenhouse gas, but the water in the atmosphere just continues to go through the water cycle.  When it reaches a certain level, there is some sort of precipitation and the water falls to Earth.

The carbon dioxide level is more worrisome to many scientists because the level in the atmosphere keeps going up and up while the amount of plant life on the Earth's surface is decreasing.  So the plants are not able to offset the difference in the atmospheric carbon dioxide concentration.  When water vapor increases, we have more rain.  When carbon dioxide levels increase, plants can take up more of it, but not enough to keep up with the increase.