Current trend of “global warming” isn’t enough to get there, says MIT scientist.
How Earth sheds heat into space
New insights into the role of water vapor may help researchers predict how the planet will respond to warming.
Just as an oven gives off more heat to the surrounding kitchen as its internal temperature rises, the Earth sheds more heat into space as its surface warms up. Since the 1950s, scientists have observed a surprisingly straightforward, linear relationship between the Earth’s surface temperature and its outgoing heat.
But the Earth is an incredibly messy system, with many complicated, interacting parts that can affect this process. Scientists have thus found it difficult to explain why this relationship between surface temperature and outgoing heat is so simple and linear. Finding an explanation could help climate scientists model the effects of climate change.
Now scientists from MIT’s Department of Earth, Atmospheric and Planetary Sciences (EAPS) have found the answer, along with a prediction for when this linear relationship will break down.
They observed that Earth emits heat to space from the planet’s surface as well as from the atmosphere. As both heat up, say by the addition of carbon dioxide, the air holds more water vapor, which in turn acts to trap more heat in the atmosphere. This strengthening of Earth’s greenhouse effect is known as water vapor feedback. Crucially, the team found that the water vapor feedback is just sufficient to cancel out the rate at which the warmer atmosphere emits more heat into space.
The overall change in Earth’s emitted heat thus only depends on the surface. In turn, the emission of heat from Earth’s surface to space is a simple function of temperature, leading to to the observed linear relationship.
Their findings, which appear today in the Proceedings of the National Academy of Sciences, may also help to explain how extreme, hothouse climates in Earth’s ancient past unfolded. The paper’s co-authors are EAPS postdoc Daniel Koll and Tim Cronin, the Kerr-McGee Career Development Assistant Professor in EAPS.
A window for heat
In their search for an explanation, the team built a radiation code — essentially, a model of the Earth and how it emits heat, or infrared radiation, into space. The code simulates the Earth as a vertical column, starting from the ground, up through the atmosphere, and finally into space. Koll can input a surface temperature into the column, and the code calculates the amount of radiation that escapes through the entire column and into space.
The team can then turn the temperature knob up and down to see how different surface temperatures would affect the outgoing heat. When they plotted their data, they observed a straight line — a linear relationship between surface temperature and outgoing heat, in line with many previous works, and over a range of 60 kelvins, or 108 degrees Fahrenheit.
“So the radiation code gave us what Earth actually does,” Koll says. “Then I started digging into this code, which is a lump of physics smashed together, to see which of these physics is actually responsible for this relationship.”
To do this, the team programmed into their code various effects in the atmosphere, such as convection, and humidity, or water vapor, and turned these knobs up and down to see how they in turn would affect the Earth’s outgoing infrared radiation.
“We needed to break up the whole spectrum of infrared radiation into about 350,000 spectral intervals, because not all infrared is equal,” Koll says.
He explains that, while water vapor does absorb heat, or infrared radiation, it doesn’t absorb it indiscriminately, but at wavelengths that are incredibly specific, so much so that the team had to split the infrared spectrum into 350,000 wavelengths just to see exactly which wavelengths were absorbed by water vapor.
In the end, the researchers observed that as the Earth’s surface temperature gets hotter, it essentially wants to shed more heat into space. But at the same time, water vapor builds up, and acts to absorb and trap heat at certain wavelengths, creating a greenhouse effect that prevents a fraction of heat from escaping.
“It’s like there’s a window, through which a river of radiation can flow to space,” Koll says. “The river flows faster and faster as you make things hotter, but the window gets smaller, because the greenhouse effect is trapping a lot of that radiation and preventing it from escaping.”
Koll says this greenhouse effect explains why the heat that does escape into space is directly related to the surface temperature, as the increase in heat emitted by the atmosphere is cancelled out by the increased absorption from water vapor.
Tipping towards Venus
The team found this linear relationship breaks down when Earth’s global average surface temperatures go much beyond 300 K, or 80 F. In such a scenario, it would be much more difficult for the Earth to shed heat at roughly the same rate as its surface warms. For now, that number is hovering around 285 K, or 53 F.
“It means we’re still good now, but if the Earth becomes much hotter, then we could be in for a nonlinear world, where stuff could get much more complicated,” Koll says.
To give an idea of what such a nonlinear world might look like, he invokes Venus — a planet that many scientists believe started out as a world similar to Earth, though much closer to the sun.
“Some time in the past, we think its atmosphere had a lot of water vapor, and the greenhouse effect would’ve become so strong that this window region closed off, and nothing could get out anymore, and then you get runaway heating,” Koll says.
“In which case the whole planet gets so hot that oceans start to boil off, nasty things start to happen, and you transform from an Earth-like world to what Venus is today.”
For Earth, Koll calculates that such a runaway effect wouldn’t kick in until global average temperatures reach about 340 K, or 152 F.
Global warming alone is insufficient to cause such warming, but other climatic changes, such as Earth’s warming over billions of years due to the sun’s natural evolution, could push Earth towards this limit, “at which point, we would turn into Venus.”
Koll says the team’s results may help to improve climate model predictions. They also may be useful in understanding how ancient hot climates on Earth unfolded.
“If you were living on Earth 60 million years ago, it was a much hotter, wacky world, with no ice at the pole caps, and palm trees and crocodiles in what’s now Wyoming,” Koll says. “One of the things we show is, once you push to really hot climates like that, which we know happened in the past, things get much more complicated.”
This research was funded, in part, by the National Science Foundation, and the James S. McDonnell Foundation.
NOTE: Try as I might, I could not locate the paper by press time. In its press release, MIT failed to include a link to the paper, DOI, or title of paper….anything that could possibly help find it at PNAS. Journalism 101 failure.
The article is deceptively written.
One has to read deeply into it to find the barely raised conclusion that a runaway greenhouse on Earth will not happen by human created CO2.
Additionally, it is written in a condescending deeply dumbed down style.
It’s a press release. That’s because they have a wide demographic. The bigger the institution, the more the press release is about self-agrandizement. That’s why we want the real paper.
Update on PNAS/DOI confusion:
So, the MIT press release jumped the gun a bit when they claimed “Their findings, which appear today in the Proceedings of the National Academy of Sciences.”
…Sorta reminds me of Arne Gunderson’s trashy lectures after Fukushima (picked up by sensational British tabloids and documentary makers) where he is claiming that every spent fuel pool in every nuclear power plant throughout the whole world is absolutely certain to come to a rolling boil until the water is gone, when it bursts into roaring flame capable of melting everything, and the spent lightly enriched uranium will somehow be drawn together as if it was somehow magnetic and its molecules will toss away the overwhelming majority of all other other molecules with evil laughter, so it can gather tightly in sufficient concentration to go ‘critical’ again without and lift itself into the air like newly-hatched spiders to cover the Earth with plumes of death that threaten all life on Earth. He made money doing this for awhile.
Every stage of the process he describes involves the most egregious assumptions about material properties, errors with whole orders of magnitude, and his unlikely scenarios chained together long past infinitesimal impossibility, with droning assurance with an emotional affectation that communicates the disaster as a certainty.
That, coupled with the propaganda principle I call ‘The animals of Bambi’s forest flee in terror’ where human beings are described as wussies who would merely cower in mute astonishment as bad things happen… it’s amazing how many parallels there are in AGW propaganda.
Research that is:
A little more honest.
A little more focused on what happens, rather than just pulling numbers from orifices.
Unfortunately, it is research that still leaves a lot to be desired; like an admission of fallibility.
This is a charade throwing around large numbers to wow and obfuscate.
In reality, there are many millions of IR radiation frequencies.
Splitting them into a fixed number appears to be arbitrary and capricious.
The fact that man applies fixed numbers to infinite concepts or constructs, e.g. time or light frequencies, is a shallow echo of real world and solar physics.
“such as convection, and humidity, or water vapor”.
Say what!?
From their wording, one wonders what they mean by convection, water vapor and humidity?
Does their model have seperate code for humidity and water vapor? Or do they run the same code twice?
Do their calculations for convection include transportation of H₂O’s other phases? H₂O liquid and solid atmospheric transportation are major atmosphere heat movement engines.
N.B. Their model description appears to focus on gaseous components of the atmosphere, while ignoring H₂O’s IR activity in all three Earth H₂O phases, vapor, liquid and solid.
Atmospheric heat transport through movement and changes between H₂O’s physical phases are significant components for all atmospheric processes.
Where does this belief come from, that greenhouse gases cease emitting radiation and forever hold heat? What do these researchers believe happens to atoms and molecules, cancelling energy emission?
“water vapor feedback”
What is this?
Is this an increase in water vapor for every miniscule increase of CO₂?
Is this some odd version of using GHG lapse rate for delaying emission of energy to space? Where, allegedly, larger and larger amounts of energy are forever trapped and unable to escape Earth.
Ah yes, the research team built an infallible omniscient model…
This smacks of using a single “Earth’s surface” to represent the globe and very narrowly defined atmosphere column absorption/emission profile.
No polar or subpolar regions.
No oceans.
Just input a temperature and the whole Earth omniscient model spits out outgoing heat. Skip all of those pesky incoming radiation details.
A) Yes, the alleged model does refute a “tipping point” nonsense; but, the article and likely the research imparts a belief that Earth’s atmosphere can easily achieve extremely high temperatures.
– i) Which indicates that their model is narrowly defined and ignores evaporation, condensation, solidification and melt.
B) Once again, researchers present narrowly defined and tailored program code as representative of Earth’s atmosphere.
Confirmation bias is strong in this crowd.
This is a charade throwing around large numbers to wow and obfuscate.
In reality, there are many millions of IR radiation frequencies.
Splitting them into a fixed number appears to be arbitrary and capricious.
Well the range of Earth’s emissions is ~2000 cm-1 so they’re quoting a resolution of ~0.006 cm-1. Water has ~52,000 lines in that range CO2 has ~190,000 lines and O3 ~300,000 lines in HITRAN. Based on their quoted 350,000 frequencies it looks like they’re calculating over a range of 1,600 cm-1
Does climate bend to ‘Tipping points’ or is it constrained by this curve?
Thanks for that graph leading to the page https://www.lenntech.com/calculators/calculators.htm . I’ve been wondering about that since getting a new indoor/outdoor thermometer w hygrometer . Frequently goes to LL ( < 10% ) during the daytime here at 2500m .
Greenhouse effect is working only if greenhouse is compact without holes. Imagine greenhouse without walls, roof only. What would be temperature increase there. Close to nothing.
Atmosphere is not compact insulator. There is hole which allows heat escape. Heat transfer by latent evaporation heat. Water is allowed to steal heat on the ground, then by quick lift skip almost all the atmosphere, go up and release condensation heat above all greenhouse gases. Moreover water is releasing its heat in its own characteristic wavelength which has poor overlap with CO2.
Poor overlap of H2O and CO2 was propagated by AGW theory supporters as reason why greenhouse effect of CO2 works. On the end it works against them. Not overlapping wavelengths of CO2 and water are causing that evaporative heat of water taken on ground is reradiated high in the atmosphere in spectrum bands mostly avoiding CO2 absorption bands.
This heat transfer is orders of magnitude above any greenhouse gas impact.
This mechanism is bypass venting our Earth greenhouse.
Greenhouse effect is working only if greenhouse is compact without holes. Imagine greenhouse without walls, roof only. What would be temperature increase there. Close to nothing.
Atmosphere is not compact insulator. There is hole which allows heat escape. Heat transfer by latent evaporation heat. Water is allowed to steal heat on the ground, then by quick lift skip almost all the atmosphere, go up and release condensation heat above all greenhouse gases. Moreover water is releasing its heat in its own characteristic wavelength which has poor overlap with CO2.
Poor overlap of H2O and CO2 was propagated by AGW theory supporters as reason why greenhouse effect of CO2 works. On the end it works against them. Not overlapping wavelengths of CO2 and water are causing that evaporative heat of water taken on ground is reradiated high in the atmosphere in spectrum bands mostly avoiding CO2 absorption bands.
This heat transfer is orders of magnitude above any greenhouse gas impact.
This mechanism is bypass venting our Earth greenhouse.
Link to the article:
http://www.pnas.org/content/early/2018/09/24/1809868115
The full: https://files.fm/u/ym9huj8k#/view/10.1073%40pnas.1809868115.pdf
Wacky World? So the Paleocene Epoch (66 to 56 mya) was wacky? Was it also zany, madcap, ridiculous, and krazy dude?
Did “things” get “complicated” in Wacky World? Is that what their model showed? Did the seas boil off into outer space 60 mya? When did they return?
Palm trees and crocodiles in Wyoming? Wacky, wacky, wacky!! Boy oh boy the Earth was for sure out of whack back then. When did we get back into whack? How did that happen? Did God do it? Gaia maybe?
Lucky for us, scienterrificals at MIT know what is and is not wacky. Why, they’re doctors of wacky and have studied wacky extensively and intensively.
Don’t you be wacky. Please de-wack yourself. Use MIT for a guide if you need to. They know wacky.
once again “scientists” claim the greenhouse effect “traps” heat … can someone pull their scientist card for such nonsense …
What about Zeller et al recent discovery which shows that all the planets temperatures can be explained by taking into consideration only two (2) things, sun distance and atmosphere pressure on the surface? Results are within 1C. This treats co2 no differently than any other gas, hence removes the GHG claims completely.
Zeller and his crew had to do things with their names to get their study printed. LOL. The “settled science” believers remain desperate.
I must admit that I ignore their stuff.
But the somewhat related view stated here: \https://motls.blogspot.com/2010/05/hyperventilating-on-venus.html seems plausible to me. That is, some greenhouse gas is needed for the surface to radiate more than it receives from the sun, but beyond a certain opacity it’s the lapse rate and size of the atmosphere that have the most effect.
I’m not saying I’ve gotten to the bottom of this, but on a qualitative level it sounds reasonable.
What about Zeller et a recent “discovery”, that all the planets’ temperatures can be determined by taking into consideration only two (2) things: Distance from sun and atmospheric pressure at the surface. Temps within 1C
This treats co2 no differently than any other gas
Almost certainly rubbish. As I understand it the GCMs all have a too-low factor for cloud cover reflectance. They have to, otherwise they can’t “validate” to the training century with the high climate sensitivity they assume.
Consequentially in the real world as temperature rises so will cloud cover due to increased convective transport of water vapour to the troposphere. Then the clouds that form will reflect more solar radiation and thus cool the planet.
The trouble with the models and clouds is they can’t afford to model them correctly because if they did they’d prove CAGW can’t happen and thus their budgets and salaries would be adjusted to zero.
The real tipping point is sustained temperature above 212 F, because the increase atmospheric pressure from the evaporated oceans would cause that temperature to be maintained – as per the following from Pierre Gosselin’s blog yesterday:
Climate Scientist Karl Zeller Sums Up The ‘Discovery’ That Pressure, Not CO2, Determines Planets’ Temps
There have been tropical reptiles and palm trees in Wyoming for the last 80 million years — up until the Ice Ages. Arecaceae and Crocodylia both arose in the Cretaceous — in Wyoming! Palms and crocs are the NORMATIVE condition for Wyoming. What’s wacky is that they are not there today.
If energy to space increases to the fourth power of increased temperature at the escape altitude, and the observed relationship between surface temperature and radiation to space is linear, the supposed water vapor retention/feedback must also be a fourth power function, no?
This seems way too strong a feedback for water.
Above we are looking up and down in a water only tropical atmosphere at about the tropopause. It can be seen that there is very little downward radiation (blue lower left), and the upward radiation peaks in intensity pretty much where CO2 does at a near surface temperature ~290K.
Modtran was expanded in range since the first image, but above the water only tropical tropopause upward radiation increases some 50 W/m2 when the surface temperature is increased 10 degrees.
When water vapor is doubled and ground temperature held constant, radiation to space does not decrease, it increases some 25 W/m2.
Modtran disagrees with this study.
https://www.google.at/search?ie=UTF-8&client=ms-android-samsung&source=android-browser&q=something+is+rotten+in+the+state+of+denmark
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When planet earth already was in a state of
“If you were living on Earth 60 million years ago, it was a much hotter, wacky world, with no ice at the pole caps, and palm trees and crocodiles in what’s now Wyoming,” Koll says. “One of the things we show is, once you push to really hot climates like that, which we know happened in the past, things get much more complicated.”
___________________________________________________
how did it make back to “normal”.
“NOTE: Try as I might, I could not locate the paper … if/when they respond, I’ll add a link to the paper. -Anthony”
Mod: Here’s the paper (paywalled).
http://www.pnas.org/content/early/2018/09/24/1809868115