# What else causes global warming? **URL:** \ **Category:** Great Debates\ **Created:** [February 28, 2018, 8:41pm UTC](https://boards.straightdope.com/t/what-else-causes-global-warming/809775 "2018-02-28T20:41:29Z")\ **Posts on this page:** 20\ **Page:** 2
**Author:** ![watchwolf49](https://avatars.discourse-cdn.com/v4/letter/w/e9c0ed/32.png) [@watchwolf49](https://boards.straightdope.com/u/watchwolf49)\ **Post date:** [March 1, 2018, 2:25pm UTC](https://boards.straightdope.com/t/what-else-causes-global-warming/809775/21 "2018-03-01T14:25:55Z")
> [@GIGObuster](#): > > [snip] … More confirmation of that from here (2015): > [Observational determination of surface radiative forcing by CO2 from 2000 to 2010 | Nature](https://www.nature.com/articles/nature14240) > Link to paper: > [http://asl.umbc.edu/pub/chepplew/journals/nature14240\_v519\_Feldman\_CO2.pdf](http://asl.umbc.edu/pub/chepplew/journals/nature14240_v519_Feldman_CO2.pdf) Thank you **GIGO** … that _Nature_ article is spot-on what I was looking for … I’ll be digesting the Feldman _et al_ letter over the weekend … > [@GIGObuster](#): > > Up to the 1940s, after that, nature remains in the background and humans are driving the warming now. > > What remains notorious is that even in the 1950’s people like Plass noted that human influence was, well, beginning to influence the thing … [snap] I was answering **Quartz’** comment about “correlation is not causation!” … of course ther’s a correlation between solar flux and global temperatures, we know the cause of this in very clear terms … Also noteworthy is that the premise of the movie _Soylent Green_ (1973) is climate change and global warming … these ideas have been around the better part of 50 years … the main difference is computers are fast enough today to run numerical models … and getting faster by the day … > [@wolfpup](#): > > I’m not sure why you’re trying to challenge either the assertion that the theoretical climate forcings arising from CO2 are well quantified or that they match observations. None of this is controversial. What is controversial is how forcings relate to changes in key climate parameters, particularly temperature, but even those arguments have well-bounded limits for climate sensitivity. > > But just to run through a sort of quick sanity check, the first-order approximation for the CO2 radiative transfer code [is given here](https://en.wikipedia.org/wiki/Radiative_forcing#Forcing_due_to_atmospheric_gas). This is a simplification of the effects of the CO2 spectral absorption lines. If you work through the math using 290 as the pre-industrial reference value for CO2 and 400 as the present value, you get an approximate predicted forcing of 1.72 W/m[sup]2[/sup] … [snip] You haven’t connected climate forcing to temperature in a quantitative way … because when you do you’ll find the logarithmic function the least of the Alarmists’ problems … I am genuinely surprised … I had thought the 1.72 W/m[sup]2[/sup] number had been already confirmed … is this really that hard to measure? … anyway, that’s the clear sky value and of course perfect atmospherics will give the theoretical value, but rarely are the atmospherics perfect and so actual forcing is substantially lower … The good news is that dealing with CO[sub]2[/sub] pollution will be easier than dealing with deforestation … ---
**Author:** ![wolfpup](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/wolfpup/32/10618_2.png) [@wolfpup](https://boards.straightdope.com/u/wolfpup)\ **Post date:** [March 1, 2018, 6:31pm UTC](https://boards.straightdope.com/t/what-else-causes-global-warming/809775/22 "2018-03-01T18:31:07Z")
> [@watchwolf49](#): > > You haven’t connected climate forcing to temperature in a quantitative way You’re right, I mentioned temperature but quantified CO2 concentrations relative to forcing rather than temperature. My original statement was “_The warming caused by the radiative transfer effects of CO2 and other GHGs and their feedbacks are well quantified and observations match the CO2 concentrations that have accumulated since industrialization_”, but what I showed was that the _ **forcing** _ due to CO2 etc. was well quantified. I did, however, say that “_What is controversial is how forcings relate to changes in key climate parameters, particularly temperature, but even those arguments have well-bounded limits for climate sensitivity_”. This is also quantifiable, but the exact quantitative relationship of CO2 forcing to temperature change under present conditions is much more complex and still the subject of some controversy. However, what is important for policy purposes is that there is a definite lower limit and the magnitude of the change and the speed with which it will happen are both significant. The most often cited metric describing this relationship is equilibrium climate sensitivity – defined as how much temperature will increase at equilibrium when CO2 doubles. There’s broad agreement that it’s between 1.5°C to 4.5°C, a range that’s been cited more or less the same way for over 20 years. The IPCC no longer cites a “most likely” value within that range. Compounding the argument is that the probability density function of ECS estimates from many sources tends to be a skewed distribution with an early peak and a long tail at the high end. A reasonable estimate of most likely ECS is to take the median (not the mode) of the distribution, so that half the probabilities are above and half below the selected point. In most analyses the median yields a most likely value for ECS of around 3°C, meaning that, when CO2 doubles, and all feedbacks are taken into account, the temperature will stabilize around 3°C warmer than the reference temperature and CO2 concentration. ---
**Author:** ![DrDeth](https://avatars.discourse-cdn.com/v4/letter/d/b487fb/32.png) [@DrDeth](https://boards.straightdope.com/u/DrDeth)\ **Post date:** [March 1, 2018, 6:44pm UTC](https://boards.straightdope.com/t/what-else-causes-global-warming/809775/23 "2018-03-01T18:44:23Z")
> [@Stranger\_On\_A\_Train](#): > > The canonical list of climate change denial and myths: [Arguments from Global Warming Skeptics and what the science really says](https://www.skepticalscience.com/argument.php) > > Please present some novel argument rather than a vague, “It could be ‘something else’,” attempt at diversion without any evidential basis. Well, of course Global Warming is also caused by a number of factors- the biggest warming gas is actually water vapor. The thing is -\* the recent rapid increase\* is certainly most caused by humans with CO2, etc. Tht doesnt mena humans are 100% responsible for all the C02 or all the water vapor or all the other greenhouse gases- they have been around since just about the start. It doesnt mean there are not other factors that coming in- long term slow cycles do certainly occur. But there is no doubt that most of the recent rapid increase is human caused. ---
**Author:** ![wolfpup](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/wolfpup/32/10618_2.png) [@wolfpup](https://boards.straightdope.com/u/wolfpup)\ **Post date:** [March 1, 2018, 7:18pm UTC](https://boards.straightdope.com/t/what-else-causes-global-warming/809775/24 "2018-03-01T19:18:53Z")
> [@DrDeth](#): > > Well, of course Global Warming is also caused by a number of factors- the biggest warming gas is actually water vapor. I realize you’re not trying to argue against AGW, but I have to point out that this example is a typical irrelevancy that one sometimes hears from climate deniers. The absolute amount of water vapor in the atmosphere globally, on average, is directly related to temperature. As temperatures rise, absolute humidity increases because the air’s capacity for water vapor increases. Generally speaking, tropospheric water vapor is not an independent climate forcing but a direct feedback that amplifies other forcings, particularly that of CO2, approximately doubling its impact. > [@DrDeth](#): > > Tht doesnt mena humans are 100% responsible for all the C02 or all the water vapor or all the other greenhouse gases- they have been around since just about the start. It doesnt mean there are not other factors that coming in- long term slow cycles do certainly occur. A good illustration of how big the human influence has been is the historic CO2 level. If you drew a chart of CO2 levels over the past million years, it would vary between a consistent low of about 180 ppm at the depth of ice ages to a consistent high of about 290-300 ppm at the peak of interglacials. If you then wanted to add modern-era CO2 to the chart, it would be completely off the chart. You’d have to expand the scale, because it’s now over 400 ppm and probably can’t be stopped before it’s well over 600 and probably 800. And those changes are occurring, not over thousands of years, but within decades. ---
**Author:** ![Silver\_lining](https://avatars.discourse-cdn.com/v4/letter/s/aca169/32.png) [@Silver\_lining](https://boards.straightdope.com/u/Silver_lining)\ **Post date:** [March 2, 2018, 2:35pm UTC](https://boards.straightdope.com/t/what-else-causes-global-warming/809775/25 "2018-03-02T14:35:59Z")
> [@scr4](#): > > Did you actually look at the plots there? If you have to throw away some of the data (namely everything after 1980 or so) to show a correlation, it’s not really a correlation, is it? But if the temperature decreased in a global sense from 2018, with 2017 and 2016 being much hotter, the short-term coloration isn’t trending upward either. That chart I listed was over decades. ---
**Author:** ![Silver\_lining](https://avatars.discourse-cdn.com/v4/letter/s/aca169/32.png) [@Silver\_lining](https://boards.straightdope.com/u/Silver_lining)\ **Post date:** [March 2, 2018, 2:42pm UTC](https://boards.straightdope.com/t/what-else-causes-global-warming/809775/26 "2018-03-02T14:42:25Z")
> [@scr4](#): > > Did you actually look at the plots there? If you have to throw away some of the data (namely everything after 1980 or so) to show a correlation, it’s not really a correlation, is it? I would not dismiss the weakening of the magnetic field being one of the causes for a very slight increase in Global warning. > [@](#): > > Earth’s magnetic field is important for climate change at high altitudes. Scientists found that changes in the Earth’s magnetic field are more relevant for climatic changes > **[Earth's magnetic field is important for climate change at high altitudes](https://phys.org/news/2014-05-earth-magnetic-field-important-climate.html)** > > New research, published this week, has provided scientists with greater insight into the climatic changes happening in the upper atmosphere. Scientists found that changes in the Earth's magnetic field are more relevant for climatic changes in the... ---
**Author:** ![Kimstu](https://avatars.discourse-cdn.com/v4/letter/k/ecd19e/32.png) [@Kimstu](https://boards.straightdope.com/u/Kimstu)\ **Post date:** [March 2, 2018, 4:01pm UTC](https://boards.straightdope.com/t/what-else-causes-global-warming/809775/27 "2018-03-02T16:01:42Z")
> [@Silver\_lining](#): > > But if the temperature decreased in a global sense from 2018, with 2017 and 2016 being much hotter, the short-term coloration isn’t trending upward either. Two or three years is far too short a timescale to detect any “trend” in global temperature, as annual temperature fluctuations outweigh small amounts of global temperature rise. Anyway, what do you mean by “if the temperature decreased in a global sense from 2018”? There isn’t any global temperature change **from** 2018 yet, because it still **is** 2018. Early in 2018, for that matter. ---
**Author:** ![Do\_Not\_Taunt](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/do_not_taunt/32/2968_2.png) [@Do\_Not\_Taunt](https://boards.straightdope.com/u/Do_Not_Taunt)\ **Post date:** [March 2, 2018, 4:46pm UTC](https://boards.straightdope.com/t/what-else-causes-global-warming/809775/28 "2018-03-02T16:46:01Z")
> [@wolfpup](#): > > because it’s now over 400 ppm and probably can’t be stopped before it’s well over 600 and probably 800. And those changes are occurring, not over thousands of years, but within decades. This - 800ppm especially - seems more like pessimism that anything grounded in scientific objectivity. The IPCC [Representative Concentration Pathways](https://en.wikipedia.org/wiki/Representative_Concentration_Pathways) are still illustrative. Only the worst one of these takes us over 800ppm by end-of-century, and the second worst takes us over 600. The third worse to ~600. There is nothing that has changed since the RCPs were developed to lock us out of any of those pathways. For what it’s worth, if I were a betting man (hey, I am, but this is too long-term of a bet to be meaningful…), I’d bet we’ll peak between 500 and 600 ppm. ---
**Author:** ![watchwolf49](https://avatars.discourse-cdn.com/v4/letter/w/e9c0ed/32.png) [@watchwolf49](https://boards.straightdope.com/u/watchwolf49)\ **Post date:** [March 2, 2018, 6:16pm UTC](https://boards.straightdope.com/t/what-else-causes-global-warming/809775/29 "2018-03-02T18:16:07Z")
> [@wolfpup](#): > > [snip] … This is also quantifiable, but the exact quantitative relationship of CO2 forcing to temperature change under present conditions is **much more complex** and still the subject of some controversy. However, what is important for policy purposes is that there is a definite lower limit and the magnitude of the change and the speed with which it will happen are both significant … [snap] That explains why I can’t find those numbers on the internet … temperature is easy to calculate with S-B if we know the emissivity values … how hard could it be to find? … just shine a light on a gas and measure the temperature … Surely, someone is working on this … ---
**Author:** ![watchwolf49](https://avatars.discourse-cdn.com/v4/letter/w/e9c0ed/32.png) [@watchwolf49](https://boards.straightdope.com/u/watchwolf49)\ **Post date:** [March 2, 2018, 6:22pm UTC](https://boards.straightdope.com/t/what-else-causes-global-warming/809775/30 "2018-03-02T18:22:44Z")
> [@Silver\_lining](#): > > But if the temperature decreased in a global sense from 2018, with 2017 and 2016 being much hotter, the short-term coloration isn’t trending upward either. > > That chart I listed was over decades. > [@Silver\_lining](#): > > I would not dismiss the weakening of the magnetic field being one of the causes for a very slight increase in Global warning. > > [Earth's magnetic field is important for climate change at high altitudes](https://phys.org/news/2014-05-earth-magnetic-field-important-climate.html) All very interesting but very difficult to study while we’re using our atmosphere as a sewer … best if we stop and let nature take it’s course … ---
**Author:** ![wolfpup](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/wolfpup/32/10618_2.png) [@wolfpup](https://boards.straightdope.com/u/wolfpup)\ **Post date:** [March 2, 2018, 8:19pm UTC](https://boards.straightdope.com/t/what-else-causes-global-warming/809775/31 "2018-03-02T20:19:07Z")
> [@Silver\_lining](#): > > I would not dismiss the weakening of the magnetic field being one of the causes for a very slight increase in Global warning. > > [Earth's magnetic field is important for climate change at high altitudes](https://phys.org/news/2014-05-earth-magnetic-field-important-climate.html) You’re misunderstanding what “climate” means in this context. The paper is talking about parts of the ionosphere at altitudes of the order of ~300 km, which for all practical purposes is outer space. What little atmosphere exists here is comprised of ionized plasma, which is naturally affected by magnetic field changes. The paper discusses changes in maximum electron density and ion temperature at these altitudes. Where do you see any linkage whatsoever to climate on earth? ---
**Author:** ![Silver\_lining](https://avatars.discourse-cdn.com/v4/letter/s/aca169/32.png) [@Silver\_lining](https://boards.straightdope.com/u/Silver_lining)\ **Post date:** [March 2, 2018, 9:40pm UTC](https://boards.straightdope.com/t/what-else-causes-global-warming/809775/32 "2018-03-02T21:40:58Z")
> [@Kimstu](#): > > Two or three years is far too short a timescale to detect any “trend” in global temperature, as annual temperature fluctuations outweigh small amounts of global temperature rise. > > Anyway, what do you mean by “if the temperature decreased in a global sense from 2018”? There isn’t any global temperature change **from** 2018 yet, because it still **is** 2018. Early in 2018, for that matter. 2017 was cooler than 2016 and 2015. ---
**Author:** ![TroutMan](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/troutman/32/6721_2.png) [@TroutMan](https://boards.straightdope.com/u/TroutMan)\ **Post date:** [March 2, 2018, 10:05pm UTC](https://boards.straightdope.com/t/what-else-causes-global-warming/809775/33 "2018-03-02T22:05:08Z")
> [@Silver\_lining](#): > > 2017 was cooler than 2016 and 2015. What does that indicate to you? Do you think this represents the start of a downward trend? Obviously you think this has some importance, so spell it out for us. ---
**Author:** ![watchwolf49](https://avatars.discourse-cdn.com/v4/letter/w/e9c0ed/32.png) [@watchwolf49](https://boards.straightdope.com/u/watchwolf49)\ **Post date:** [March 2, 2018, 10:07pm UTC](https://boards.straightdope.com/t/what-else-causes-global-warming/809775/34 "2018-03-02T22:07:54Z")
> [@Silver\_lining](#): > > 2017 was cooler than 2016 and 2015. And February will be cooler than July … tomorrow morning will be cooler than this afternoon … that’s all the subject of dynamic meteorology … Global warming is based on the average temperature between 1968 and 2017 being higher than the average from 1918 to 1967 … and the temperature average will be even higher from 2018 to 2067 … that’s the subject of climatology … See the difference? … in the first case we use _dt_ as our time interval … in the second we use 50 years … ---
**Author:** ![wolfpup](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/wolfpup/32/10618_2.png) [@wolfpup](https://boards.straightdope.com/u/wolfpup)\ **Post date:** [March 2, 2018, 10:11pm UTC](https://boards.straightdope.com/t/what-else-causes-global-warming/809775/35 "2018-03-02T22:11:50Z")
> [@Silver\_lining](#): > > 2017 was cooler than 2016 and 2015. Where I live, today was cooler than yesterday and the day before, but I’m pretty sure that spring and summer are coming! 2016 was the [hottest year on record in NOAA’s 138-year history](https://www.ncdc.noaa.gov/sotc/global/201713). 2015 was the second hottest on record, and 2017 the third hottest. Temperature trends are not uniform or linear year-to-year, but the long-term trend is unequivocal, and so are the reasons for it. I have no idea what you’re trying to prove with that statement. ---
**Author:** ![GIGObuster](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/gigobuster/32/421_2.png) [@GIGObuster](https://boards.straightdope.com/u/GIGObuster)\ **Post date:** [March 2, 2018, 10:15pm UTC](https://boards.straightdope.com/t/what-else-causes-global-warming/809775/36 "2018-03-02T22:15:31Z")
> [@Silver\_lining](#): > > 2017 was cooler than 2016 and 2015. So the new 1998 is 2016, that figures, it is the same old flawed and discredited argument that skeptical scientists (the few that remain) **warned** their followers not to use: “You’ve all seen articles say that global warming stopped in 1998. Well, with all due respect, that’s being a little bit unfair to the data…it was a huge El Niño year, and the sun was very active in 1998…make an argument that you can get killed on, and you will kill us [skeptics] all…if you lose credibility on this issue, you lose the issue.” Patrick Michaels 6 September 2009 Why it is flawed is explained here: > **[The Escalator](https://skepticalscience.com/graphics.php?g=47)** > > Examines the science and arguments of global warming skepticism. Common objections like 'global warming is caused by the sun', 'temperature has changed naturally in the past' or 'other planets are warming too' are examined to see what the science... ---
**Author:** ![watchwolf49](https://avatars.discourse-cdn.com/v4/letter/w/e9c0ed/32.png) [@watchwolf49](https://boards.straightdope.com/u/watchwolf49)\ **Post date:** [March 2, 2018, 10:24pm UTC](https://boards.straightdope.com/t/what-else-causes-global-warming/809775/37 "2018-03-02T22:24:55Z")
The hottest year we know of was 250,000,000 BC … although it’s fair to assume 4,700,000,000 BC was even hotter … but let’s not nitpick among friends eh? … ---
**Author:** ![wolfpup](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/wolfpup/32/10618_2.png) [@wolfpup](https://boards.straightdope.com/u/wolfpup)\ **Post date:** [March 2, 2018, 10:57pm UTC](https://boards.straightdope.com/t/what-else-causes-global-warming/809775/38 "2018-03-02T22:57:06Z")
> [@GIGObuster](#): > > So the new 1998 is 2016, that figures, it is the same old flawed and discredited argument that skeptical scientists (the few that remain) **warned** their followers not to use: > > “You’ve all seen articles say that global warming stopped in 1998. Well, with all due respect, that’s being a little bit unfair to the data…it was a huge El Niño year, and the sun was very active in 1998…make an argument that you can get killed on, and you will kill us [skeptics] all…if you lose credibility on this issue, you lose the issue.” > Patrick Michaels > 6 September 2009 > > Why it is flawed is explained here: > > [The Escalator](https://www.skepticalscience.com/graphics.php?g=47) As an aside, Patrick Michaels is a funny guy, though not intentionally. He’s a typical climate change denier: a paid shill for the fossil fuel industry, and works as an advisor to the right-wing Cato Institute that was founded by Charles Koch to disseminate right-wing and libertarian propaganda. Michaels has managed to distinguish himself by [being wrong about practically everything](https://thinkprogress.org/patrick-michaels-catos-climate-expert-has-history-of-getting-it-wrong-f20e9196160e/). ---
**Author:** ![GIGObuster](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/gigobuster/32/421_2.png) [@GIGObuster](https://boards.straightdope.com/u/GIGObuster)\ **Post date:** [March 3, 2018, 1:04am UTC](https://boards.straightdope.com/t/what-else-causes-global-warming/809775/39 "2018-03-03T01:04:29Z")
> [@watchwolf49](#): > > The hottest year we know of was 250,000,000 BC … although it’s fair to assume 4,700,000,000 BC was even hotter … but let’s not nitpick among friends eh? … And before anyone else gets the wrong idea, there are good natural explanations of why was that… the same warming gases were present then, what climate scientists are warning about nowadays. For the environment it makes no difference that there were released by nature before (in a long period of time, but eventually at deadly levels), it is the same stuff and the environment reacts to the accumulation of global warming gases (that acidify the oceans too) just like in the past. > **[Alarming new study makes today’s climate change more comparable to Earth’s...](https://skepticalscience.com/Lee-commentary-on-Burgess-et-al-PNAS-Permian-Dating.html)** > > The Permian Mass Extinction 251.9 million years ago, otherwise known as “The Great Dying,” was the closest this planet has come to extinguishing all complex life on Earth. Around 90% of all species died out in this single event, a worse toll even... > [@](#): > > Burgess et al’s paper brings the Permian into line with many other global-warming extinction events, like the Triassic, the Toarcian, the Cretaceous Ocean Anoxic Events, The PETM, and the Columbia River Basalts, whose time frames have been progressively reduced as more sophisticated dating has been applied to them. They all produced the same symptoms as today’s climate change – rapid global warming, ocean acidification, and sea level rises, together with oxygen-less ocean dead zones and extinctions. They were all (possibly excluding the PETM - see below) triggered by rare volcanic outpourings called “Large Igneous Provinces,” (LIPs) that emitted massive volumes of CO2 and methane at rates comparable to today’s emissions. The PETM may also have been triggered by a LIP, although that is still debated. > > Can we seriously expect Earth’s climate to behave differently today than it did at all those times in the past? > > Some have pointed out that since we began our modern climate change in an “icehouse” era with ice sheets to melt and low starting CO2 levels, we might not generate a Permian-like hothouse. In addition, since the Permian, calcareous algae have changed the way deep oceans process carbonate, providing more of a buffer. But that buffer only comes into play if the deep oceans come into play, which most estimates consider won’t happen for a few more centuries. > > All in all, the parallels between the many mass extinction events in the geological record and today’s climate change offer no comfort about the legacy we’re leaving for our children and our grandchildren. Rather they stand as signposts for an increasingly scary future. ---
**Author:** ![jshore](https://avatars.discourse-cdn.com/v4/letter/j/b5e925/32.png) [@jshore](https://boards.straightdope.com/u/jshore)\ **Post date:** [March 3, 2018, 1:18am UTC](https://boards.straightdope.com/t/what-else-causes-global-warming/809775/40 "2018-03-03T01:18:19Z")
> [@watchwolf49](#): > > That explains why I can’t find those numbers on the internet … temperature is easy to calculate with S-B if we know the emissivity values … how hard could it be to find? … just shine a light on a gas and measure the temperature … Surely, someone is working on this … There’s a lot wrong in this one statement/question of yours. (1) First of all, it misses the point: The point being made is that the radiative effect of CO2 (while way more complicated than you have imagined here) is pretty well-understood. What is not as well understood is the feedbacks in the climate system: For example, as the Earth warms, some land and sea ice melts in the polar regions and that decreases the reflectivity of the Earth, so this tends to cause more warming. This is called “a positive feedback” (“positive” because it amplifies the original effect). Similarly, as the Earth warms, more water vapor evaporates into the atmosphere and its concentration thus increases and, since water vapor is a greenhouse gas, that causes more warming, another positive feedback. Finally, there are clouds, i.e., water vapor condensed into droplets…which are complicated because clouds can cause both cooling (by reflecting solar radiation) and warming (by increasing the greenhouse effect). And, furthermore, how cloudiness will change as the Earth warms is not easy to predict. So, it turns out that the cloud feedback is the biggest source of uncertainty in determining the climate sensitivity, i.e., how much the Earth will warm in response to, say, a doubling of CO2 levels. [And, there are feedbacks to other parts of the process too since, for example, a warming Earth can cause changes in the uptake of CO2 by plants and oceans or can cause the release of methane from melting permafrost and so forth.] (2) Second of all, the radiative effects of CO2 are more complicated than Stefan-Boltzmann. That applies to radiating surfaces of opaque objects. Here, we are talking about a gas that radiation passing through can be absorbed and radiation can also be emitted. Also, for gases like CO2, the emissivity / absorptivity tend to occur in sharp lines and bands, which are quite complex. Nonetheless, as I (and I believe **wolfpup** ) noted, the radiative transfer codes that compute the radiative forcing due to increases in CO2 are quite well-advanced and the uncertainties in this radiative forcing is considerably better determined than the next step of figuring out how that radiative forcing translates into a change in temperature (where the feedbacks come in). [Previous page](https://boards.straightdope.com/t/what-else-causes-global-warming/809775.md?page=1) [Next page](https://boards.straightdope.com/t/what-else-causes-global-warming/809775.md?page=3)