Quote:
Originally Posted by DRob4JC
Some gases are subject to absorption as well.
I don't disagree that greenhouse gases move about the earth. If the wind/jet stream is blowing them around the earth - how are they able to insulate the heat radiated from earth?
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Okay...I'm back...later than I said I'd be.
So, here's what leads me to believe humans are causing a noteworthy percentage of global warming:
#1. NASA says it's happening. They are a respectably organization. Therefore, I figure I have a responsibility to either blindly accept whatever they say, or remain neutral until I've researched something that gives me reason to distrust their findings. I've therefore been more wary of climate-change skeptic arguments...taking time to research arguments pointing out their flaws, whereas with arguments for why humans are likely causing climate change, it's generally sufficient to me to just find multiple large, seemingly respectable organizations coming to similar conclusions.
#2. Skepticalscience.com Their arguments section, here,
https://skepticalscience.com/argument.php has 197 arguments made by climate change skeptics and counters to those arguments. I've found many of these arguments to be unsatisfactory in terms of not explaining things as fully as I'd have preferred, or in ways I don't understand...but they usually contain keywords that I can use to do further research, as well as links to other useful sources. If you want to do your own research, this is a wonderful source due to so much information being contained in one spot.
#3. So...finally getting around to your specific statement, if you have a bathtub of cold water, and you keep adding hot water into it, that hot water disperses throughout the bathtub. I'm thinking that's how greenhouse gasses work. They'll spread out, but they'll still be here, so they'll accumulate. I had to look up this link to understand why atmospheric gases don't just all float into space. I found it useful:
https://www.quora.com/Why-wouldnt-Ea...ape-into-space
I didn't do any of the math there. I just kind of assume it's correct...but in a bathtub, we tend to see the whole bathtub getting hotter. Though, to some degree, if you put the cold water in first the bottom will remain cooler...but eventually that heat is going to spread downwards too, if you put enough hot water in or wait long enough. You can speed up that process by mixing the water. Gases are considerably lighter than water, and tend to disperse and spread and mix more easily, as does heat that moves through them.
They'll still be in the atmosphere of Earth though, most of the time, usually floating around because the higher they go up, the colder Earth's atmosphere becomes, and the more likely cool off, lose energy, and gravity will pull them down again. The more chemicals are in Earth's atmosphere, the more chance there is that they'll end up somewhere that reflects heat down onto a thermometer, other temperature-detecting device, or a human city. Some of them will escape into space. From what I've read most of it won't though.
The two gases that most concern people who study global warming are methane and C02. Methane decays in the atmosphere after a few years, but it holds more heat on Earth before it goes. C02 remains in the atmosphere for much longer. Methane from human activities is often produced by livestock, such as cows. C02 produced by human activities is often produced by the burning of fossil fuels.
When energy comes from the Sun to Earth, some of it is reflected back into space. Some of it is absorbed by Earth's surface. This is later re-emitted as infrared radiation which can carry heat through empty space. I got that data from here:
https://www.answers.com/Q/How_is_Car...greenhouse_gas
C02, and many atmospheric gases, tend to let sunlight pass through it. C02 to, however, tends to re-absorb the infrared radiation heading back towards space from the Earth's surface and reflect some of it back to Earth. Methane, I assume, works similarly:
https://www.reddit.com/r/askscience/..._at_the_earth/
Water vapor is also an important greenhouse gas, helping to hold in heat...but most of that only increases in the atmosphere after something else already increased heat further to evaporate more of it, so C02 and Methane are what people are concerned about.
C02 increases in the atmosphere due to increased temperatures too though...through ocean outgassing. The warmer the ocean gets, the more C02 emerges from it into the atmosphere. That's believed to be part of past climate changes in interglacial periods, like the last interglacial period, the Eemian, an interglacial period that began about 130,000 years ago. These interglacial and following glacial periods occur cyclically, taking tens of thousands of years for the full round to complete. It's thought...though I've never understood this well...that changes in the Earths position, known as Milankovitch cycles, cause temperature changes on Earth due to certain parts of it getting more sunlight for longer...or something like that. I don't get it. What I do get though, is that, in the beginning of interglacial periods temperature rises. Following this is a C02 rise due to oceans outgassing C02, and then the temperature continues to rise for a time, and C02 continues to increase as a kind of feedback loop. What I've not been able to understand...is why temperature falls again. Maybe I could figure that out with more research.
People say that the fact that, in past interglacial periods, temperature rose before there were C02 increases, means that C02 doesn't cause global warming. That's not true though, because I think the thought is that temperature and C02 function more like a feedback loop, with heat increasing temperature and temperature increasing C02 output. Some factors that probably have something to do with interglacial periods eventually ending, and Earth's temperature cooling again, are factors like...I assume warmer, more humid temperatures would be better for plant growth, and more plants absorb more C02. I haven't looked into this much. I'm not sure there is firm knowledge about why interglacial periods end.
But moving on from that...
*There has been no upward, long term trend, in the sun's energy output since the 1970s. This data comes from NASA:
https://climate.nasa.gov/faq/14/is-t...lobal-warming/
However, Earth's average global temperature is still rising. This can be found by looking for the highest temperatures on record. You'll find that most of the higher ones have occurred recently. This can also be found by just looking for various sources that it's rising. They're all over the place. Feel free to verify their findings yourself. I've just kind of seen enough of them from seemingly worthy sources that that's good enough for me.
*Any form of Earth warming that doesn't stem from the Sun is pretty miniscule, and local. For Earth to warm, it's always going to have something to do with either getting more energy from the sun, or more heat energy from the sun being prevented from reflecting back into space, or less energy from the sun being reflected back into space initially, or something to do with getting more solar energy or keeping it here better. C02 and Methane increases do that. Water vapor does that too, but again, that doesn't increase much unless warmer temperatures caused by something else are already happening.
*According to NASA, since 1958 C02 in the atmosphere has increased by 24%. I haven't bothered to look up how they arrived at this conclusion yet...but now you know what to look up if you want to:
https://climate.nasa.gov/400ppmquotes/
*Natural forces on Earth can produce C02, such as volcanoes or the aforementioned ocean outgassing of it that happens in warmer temperatures...but that ocean outgassing needs something to increase warming temperatures first. Volcanoes can pump lots of C02 into the atmosphere, but it's still considerably less than humans pump into the atmosphere. According to the United States Geological Survey:
VANCOUVER, Wash. — On average, human activities put out in just three to five days, the equivalent amount of carbon dioxide that volcanoes produce globally each year. This is one of the messages detailed in a new article "Volcanic Versus Anthropogenic Carbon Dioxide" by Terrance Gerlach of the U.S. Geological Survey appearing in this week's issue of Eos, from the American Geophysical Union.
https://archive.usgs.gov/archive/sit...p-ID=2827.html
So...so far as I've read, nobody can think of anything that would be resulting in Earth warming, except for human activities, except for stuff that need Earth to warm before it starts warming Earth. Ice caps melting could increase Earth's temperature by reflecting less heat back into space...but of course, temperatures have to rise to melt them first, or volcanic activity has to happen. Volcanic activity will often, at least over the sort term, cool the atmosphere down by pushing reflective materials high into the atmosphere...although it will increase C02 in the atmosphere too, but like I've mentioned, volcanic activity amounts to much less C02 increase than human activity.
The only reason I could understand for why Earth's temperature might be increasing as much as it is, if not for human activity, is maybe if it's some part of the Milankovitch cycle, or something I don't understand yet. I don't understand Milankovitch cycles well though. What I keep reading is that the current changes are happening too fast to be part of Milankovitch cycles. I'm not sure why yet.
But nobody seems to have a good idea for why global warming might be happening if it a noteworthy percentage of it is not caused by humans, so far as I can tell.
Also, regarding why human livestock produces more methane than other organisms...apparently cow digestive systems in particular just produce lots of methane. I found that out here:
Do Cow Farts Really Significantly Contribute to Global Warming?
Some of the more common arguments I've heard for why global warming isn't caused by humans are the idea that in Earth's ancient past, there was much more C02 in the atmosphere than there is now, and that didn't lead to a Venusian state where there's global warming spiraling out of control. One factor that might have not resulted in that happening is that the sun would have been cooler. From what I understand, the sun just naturally increases luminosity with time. The time period people often talk about when they say that often is a time period a billion or more years ago. That's the type of time scale we need for the sun's decreased luminosity due to being younger to matter. That kind of natural glowing brighter with time won't affect us in our lifetimes. I found out about that somewhat here, although I'd heard about that stuff before from other sources, which I've forgotten the location of:
https://www.sciencedaily.com/release...0918092804.htm
What I hear most concern about though, is not Earth spiraling onto a Venusian state, but rather Earth just becoming warmer to the point where icecaps are melted and we get summers that make certain areas that currently contain lots of people difficult to live in. We really don't need much hotter temperatures for areas to be survivable in, but not really habitable. We currently have places like Death Valley where temperatures have reached 130 degrees Fahrenheit. That's not a problem there...but if highly populated cities start reaching dramatically higher summer temperatures, that could cause a lot of problems.
Also, there are more long term effects and feedback loops (such as methane underneath Antarctica being released due to melting) that could have unpredictable effects...and really, even if we stopped all C02 output and Methane output from our livestock today, that'd just stop additional greenhouse gasses from being added. It would take awhile for those to leave the atmosphere, and for feedback loops like ocean outgassing, to cool Earth down again...and the way things are going, it seems like there is a solid chance humanity will increase C02 output before it decreases it. Nuclear power is an option for energy that doesn't pump greenhouse gases into the atmosphere...but that has some less-than-desirable side effects. From what I understand, the main problem with solar and wind power is that we can't store much of it for long. I know batteries can be expensive. I'm not sure how expensive though...but I know most of the country currently doesn't have much storage capacity for power for wind and solar.
I found out about a concept for storing solar energy for a few hours longer than usual here:
https://www.npr.org/sections/alltech...an-we-store-it
The big solution everybody is looking forward to, which remains on the horizon, is fusion power. They can already produce the incredibly high temperatures needed for this...it's just that right now it takes more energy to produce the fusion reaction than the energy that comes out of it. It'll take some number of decades to get to the point where it provides more energy than goes into it though...assuming it eventually happens. I hear they're getting better at it though. That could, hopefully, result in power sources that neither produce nuclear waste nor C02.
But even if we do invent usable fusion power plants, there's still a lot of existing C02 in the atmosphere, and there's still methane to deal with, and humanity's perpetually growing larger.
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