78

In a nutshell: The radiation that enters is shortwave radiation from the sun. Solar radiation is dominated by visible (as well as UV and near infrared) radiation with a wavelength mostly between 0.2 µm and 2 µm. This wavelength is determined by the temperature of the Sun, in the order of 6000 K. For visible radiation (roughly between 0.4 µm and 0.7 µm), ...


40

Your question about water vapour is quite a common one among people learning about the greenhouse effect. Once you discover the relevant proportions of water vapour and CO2 in the atmosphere, it's perhaps natural to assume that the CO2 can't be playing a major role. In reality it doesn't work like this, for at least a couple of reasons. First, let's look at ...


39

There looks like legitimate cause for further study, preferably by scientists breathing air under 950 ppm $\small\mathsf{CO_2}$ (this study showing a 15% decline in cognitive ability at this level). Because it is not known what mechanisms are involved in this decline in cognitive ability it is not clear if there are threshold levels, with step changes in ...


26

The reason the atmosphere (including GHGs) stays attached to the earth is gravity. This is called the Hydrostatic Equilibrium. There is one GHG that this does not fully apply to: water vapor. While water vapor can be considered to be in hydrostatic balance, the fact that it undergoes a phase change (and becomes dissociated if it reaches too far up) prevents ...


25

Gerrit's got the technical answer; I'm going to answer for a layperson. There are two ways objects lose heat. The first, and the way people are most familiar with, is conduction. Something touches something else, and the hotter material transfers some of its heat to the colder material. It's why you rapidly lose heat if you wade into cold waters: your ...


22

To add to Gerrit's excellent answer, I'd like to add a couple more Images. Images always help clarify things for me. Firstly, this one shows the spectrum light coming from the sun in red. The peak is in the visible range*. It also shows the thermal radiation from the earth in blue. This is in the infrared range. Below, it shows how different gases allow ...


22

A molecular gas is a good infrared absorber if it has several atoms (not just 2, like O2 and N2) or if it is hetero-nuclear (e.g. CO and NO). These type of molecular arrangements allow more infrared energy to be absorbed because there are more vibrational states that are possible. Yes, ammonia fits that description, but it is not long-lived in the ...


14

Trapping compounds and changing composition are two very different things. The composition of an atmosphere is set by equilibrium chemistry. Equilibrium chemistry can be understood as mapping of a set of input atoms into molecules and remaining atoms. For example, at the given numbers of N, O, C, H... and given temperature and pressure, one will always find ...


13

CO$_2$ doesn't significantly interact with solar radiation or UV, and doesn't store any significant amount of heat. What CO$_2$ effectively does is scattering infrared radiation emitted by the Earth, and such radiation is emitted day and night. Let me explain this: All objects emit a type of radiation called black body radiation. And the color (wavelength) ...


12

Borrowing an explanation from one of my other answers, the basic mechanism of the greenhouse effect is roughly as follows (note this is also a simplified model) The Earth is in (to all intents and purposes) a vacuum, so it can only gain or lose heat via radiation. The sun emits most of its radiation at visible and UV wavelengths. The Earth's ...


11

Experiments don't necessarily prove things, per se; and in particular, a single experiment tends not to prove anything - at the very least, replication of the experiment is required. Experiments provide contributory evidence. Confidence in a hypothesis can come about from a combination of theory, lab experiments and natural experiments. Our knowledge about ...


9

Let's just talk about cattle here and ignore other factors related to cattle production for now. The current cattle number (93 million) you found is probably the total number of dairy cow and beef cattle. In your argument, it is possible that bison has much more emission than cattle on pasture. But the emission from cattle in feedlot and dairy farm is much ...


8

OK it depends a lot on what exactly you mean. There is a known problem with people talking about "carbon" / "atmospheric carbon" / "Carbon Dioxide" and using the terms imprecisely - so there is often a confusion about which exact chemical species is being discussed. Tonnes of C to CO2 is (as you correctly stated) a conversion based on molecular mass, but ...


7

The short answer is that greenhouse gases occur at all levels in the atmosphere. However, the concentrations can vary with altitude. In the case of greenhouse gases that are always in a gaseous state like CO2, Methane and Nitrous oxide, they are evenly distributed throughout the lower atmosphere (i.e. troposphere and stratosphere below ~20km), (this question ...


7

The short answer to your question really is just this: Yes, CO2 causes global warming. There are many resources out there on the internet that explain this in about as much detail as you can tolerate, and whatever we could answer here does not come close to what others have already collected. I would suggest you start at the wikipedia page on global warming ...


7

An easy calculation is to start with the solar constant, the power (energy per unit time) produced by solar radiation at a distance of one astronomical unit. This is 1.361 kilowatts per square meter. The surface area of the Earth is $4\pi R^2$, where $R$ is the radius of the Earth, while the cross section of the Earth to solar radiation is $\pi R^2$. Thus ...


7

To see why we can't perform an experiment in lab conditions to verify the greenhouse effect, we need to start by considering how the [rather badly named] greenhouse effect operates: The Earth is in (to all intents and purposes) a vacuum, so it can only gain or lose heat via radiation. The sun emits most of its radiation at visible and UV wavelengths. The ...


7

There is no doubt that the sooner the mitigation effort happens, the greater will be its impact. In other words, the impact on year 2100 climate of the sequestration of 20 billion tons $\ce{CO2}$-eq right now, is much bigger than the impact that the same action will have in 30 years from now. Therefore, a mitigation action today is much cheaper than one ...


7

The common factor among Greenhouse gases is that they absorb and scatter infra-red light. The Greenhouse effect is caused when energy coming in from the sun is prevented from escaping again. The Sun emits light primarily in the visible spectrum, with some UV and infra-red, most of which is absorbed by the Earth. This causes the Earth to heat up and in ...


7

Two recent studies tend to contradict the 2016 study mentioned in Ken Fabian's answer. Acute Exposure to Low-to-Moderate Carbon Dioxide Levels and Submariner Decision Making (June 2018) reports: METHODS: Using a subject-blinded balanced design, 36 submarine-qualified sailors were randomly assigned to receive 1 of 3 $\small\mathsf{CO_2}$ exposure conditions (...


6

The Faint Young Sun Paradox - how greenhouse gases can keep a planet warm: When the Earth formed 4.5 billion years ago the Sun was around 30% less luminous than it is today and it has increased steadily since, based on well established models of solar evolution. Simple energy balance models of the Earth show that, with a similar atmosphere to today, the ...


5

There is no simple relationship since it all depends on the frequency (IR spectral lines for most species of molecules are a mess). The most direct and precise way of calculation is through line-by-line calculation from a large spectrum database. The atmospheric column will be very different based on angle off normal, weather, and even time of day (water ...


5

I found a great paper named Remote Sensing of Particulate Pollution from Space: Have We Reached the Promised Land? and collected some remote sensing instruments doing CH4 measurement in the chart below. It contains the information about the satellite, orbit types, instrument and the data time-range. Satellite Orbit Instrument Years ...


5

The idea of a carbon sink is a bit misunderstood here. The idea of a carbon sink is a reduction of carbon that comes from the atmosphere. It must “fix” carbon that is already in the air. Trees are a carbon sink, for the most part, because their mass is made of of carbon obtained from The atmosphere. Unless the plastic formation process you are thinking of is ...


5

I think you’re not far off with your understanding, but maybe I can put in a few comments to make things clearer. I often get confused because most diagrams for the Earth energy budget and net radiation balance show more infrared leaving the surface than is ever supplied by solar radiation at the top of the atmosphere in the first place… As you can see, ...


5

I've looked into this briefly and noticed a few things that are worth pointing out. First, your EPA table looks like it was based on Table 8 of this EPA pdf: https://www.epa.gov/sites/production/files/2018-03/documents/emission-factors_mar_2018_0.pdf There’s a note in the table that, Air Travel factors from 2017 Guidelines to Defra / DECC's GHG ...


5

You are correct that normally you see a net positive value of GHGs from land use change. However, if forests are grown or revegetated, it is considered a sink (and negative GHG value). This paper says that China has undergone a net increase in forest. The results sections says: The land-use data derived from Landsat Thematic Mapper (TM) imagery from 1990 ...


4

Tropospheric ozone is a significant greenhouse gas (see e.g. IPCC AR4) and has well established negative effects on crop yields. For example, Van Dingen et al (2009) evaluated yield losses of up to about 15% globally, depending on the crop.


4

It depends on the wavelength. The figure shows the most absorbing species between 6 and 16 µm for a U.S. standard tropical atmosphere (Note: this figure does NOT include the Earth's surface!). Absorption data is taken from Anderson et. al (1986) and simulations are performed with the open-source Atmospheric Radiative Transfer Simulator (ARTS; Eriksson et ...


4

Ozone is indeed a greenhouse gas. But not due to its capacity to absorb/scatter UV radiation, but instead due to its capacity to absorb infrared radiation. In contrast with other greenhouse gases (Like $CO_2$ or Methane), the spectral absorption bands of Ozone are not confined to the infrared part of the spectrum, there are ozone absorption bands also the UV ...


Only top voted, non community-wiki answers of a minimum length are eligible