Slashdot Mirror
Extreme CO2 Levels Could Trigger Clouds 'Tipping Point' and 8C of Global Warming (carbonbrief.org)
If atmospheric CO2 levels exceed 1,200 parts per million (ppm), it could push the Earth's climate over a "tipping point", finds a new study. This would see clouds that shade large part of the oceans start to break up. From a report: According to the new paper published in the journal Nature Geoscience, this could trigger a massive 8C rise in global average temperatures -- in addition to the warming from increased CO2. The only similar example of rapid warming at this magnitude in the Earth's recent history is the Paleo-Eocene Thermal Maximum 55m years ago, when global temperatures increased by 5-8C and drove widespread extinction of species on both the oceans and land.
However, scientists not involved in the research caution that the results are still speculative and that other complicating factors could influence if or when a tipping point is reached. The threshold identified by the researchers -- a 1,200ppm concentration of atmospheric CO2 -- is three times current CO2 concentrations. If fossil fuel use continues to rapidly expand over the remainder of the century, it is possible levels could get that high. The Representative Concentration Pathways 8.5 scenario (RCP8.5), a very high emissions scenario examined by climate scientists, has the Earth's atmosphere reaching around 1,100ppm by the year 2100. But this would require the world to massively expand coal use and eschew any climate mitigation over the rest of this century. Further reading: A state-of-the-art supercomputer simulation indicates that a feedback loop between global warming and cloud loss can push Earth's climate past a disastrous tipping point in as little as a century.
However, scientists not involved in the research caution that the results are still speculative and that other complicating factors could influence if or when a tipping point is reached. The threshold identified by the researchers -- a 1,200ppm concentration of atmospheric CO2 -- is three times current CO2 concentrations. If fossil fuel use continues to rapidly expand over the remainder of the century, it is possible levels could get that high. The Representative Concentration Pathways 8.5 scenario (RCP8.5), a very high emissions scenario examined by climate scientists, has the Earth's atmosphere reaching around 1,100ppm by the year 2100. But this would require the world to massively expand coal use and eschew any climate mitigation over the rest of this century. Further reading: A state-of-the-art supercomputer simulation indicates that a feedback loop between global warming and cloud loss can push Earth's climate past a disastrous tipping point in as little as a century.
Climate change is real, but you need to read any single study or model with a bit of a "let's see if this gets confirmed by other groups" before believing it.
This is the flip side of that "scientific consensus" thing that the deniers keep not understanding. Science is about replication, and the real science comes when other scientists look at a result and say "yes, that makes sense, we can confirm it with our own modeling and measurements."
This is one group, with one model. Too early to call it doomsday yet.
As someone who has a degree in botany and has worked in greenhouses that were maintained at 1500ppm. You should know that CO2 levels become dangerous at 5000 ppm, not 1200ppm.
It becomes dangerous to life and health at 40,000ppm.
https://www.cdc.gov/niosh/npg/...
From the abstract it looks like a doomsday prediction. Predicting an 8 K increase (+265c) in global temperature is an extraordinary claim and would require extraordinary evidence.
It's not even an extraordinary claim; it's an extraordinary hypothesis.
Past the doomsday headline, the story says :
"The paper emphasises that large uncertainties remain and the results they find are very much preliminary. Because they are using a high-resolution large-eddy simulation their model lacks many other factors contained in global climate models that operate over larger geographic scales.
"Specifically, climate models suggest that large-scale subsidence in the atmosphere – colder air becoming denser and moving towards the ground – weakens as the world warms. This has the effect of lifting up and cooling cloud tops, which counteracts possible stratocumulus breakup. While the paper tries to account for this, the weakening of subsidence that occurs is uncertain and varies across climate models."
Really, I'm not sure why this is even a story making the news. "Here's some scientists trying to figure out feedback loops in a greenhouse regime that is far from where we currently are, and here's an possible result that is interesting but has yet to be rigorously modelled, much less tested."
The problem here is that studies like this are based on *simulations* not observations of repeatable experiments.
True. It's a math model and should be treated as such. Simulations can be very useful but it's important to know the limits and assumptions that go into the model.
What we have here is a set of theories, which really cannot be proven beyond doubt.
Not true. Presuming the model is accurate it should be making testable predictions about what will happen as the climate chances in the coming years. If the model predictions fits the data we gather well then we have reasonable confidence that it is accurately modeling the real world. Problem is that because the consequences of letting climate change run unchecked are potentially so severe (presuming the model is accurate) we cannot risk actually testing it fully so at some point we'll have to extrapolate and take actions. But we're going to find out at least the early predictions whether we want to or not because some changes are already too late to stop.
If we are being honest here, climate change science is, at best, an educated guessing game, not a proven beyond a doubt set of scientific laws, and specifically I mean "man made climate change."
No it really is not just a guess unless you think every hypothesis is "just a guess". A lot of the science in the field is simply documenting changes that absolutely ARE occurring, many of which were predicted by those same models that you are calling guesswork. The model makes predictions which absolutely can be checked.
The critics of this science have some valid points. Past high profile predictions of our demise from climate change have been wildly over blown, there seems to be a bias towards "making news" in order to get research grants, and little attention is paid to the views of those who disagree with the consensus.
Most of the critics do not actually make or hold valid counter points. They mostly simply are seeking to reinforce their confirmation bias for various reasons. If they were serious about disputing the science the way to do that is present their own alternative testable hypothesis and back it up with data. The scientists are doing this and the critics by and large are not. Since the critics cannot be bothered to actually do the science their opinions (rightly) get ignored.
Simulations have serious limits.
Yes they do. That doesn't mean they are useless. I used to do simulations for a living in a previous job. There is a famous saying that "all models are wrong but some models are useful". If you insist on perfection in the climate models despite them giving you good and actionable data, you are completely missing the point. Newtonian physics isn't the most perfect model we have but it's still extremely useful and gives reasonably accurate testable predictions. A lot of the climate science is throwing off a lot of very useful data and we ignore it at our peril.
This is actually several dozens of groups coming up with similar modeling and conclusions over the last few years, though yes they differ a small bit they are all saying the same thing. It's not one single study saying this. False characterization.
Not merely dozens of groups, there are hundreds of groups running climate models (possibly thousands: the main models are open source.).
They are all saying the same thing, if by that you mean "human generated greenhouse gasses, primarily carbon dioxide, are increasing the Earth's greenhouse effect, and having a warming effect on the climate."
Yes, that part is a clear scientific consensus, well understood, and replicated by many groups.
It is this new result (this paper), suggesting a new feedback mechanism only operating at much higher carbon dioxide levels, of which I am saying "a single study".
And not merely one study: it is one study of which the authors of the study themselves emphasize how preliminary the results are.
Triassic: 1750 ppm CO2. Temp 3 C above modern level.
Jurassic: 1950 ppm CO2. Temp 3 C above modern level.
Cretaceous: 1700 ppm CO2. Temp 4 C above modern level.
Paleogene: 500 ppm CO2. Temp 4 C above modern level.
Neogene: 280 ppm CO2. Temp 0 C above modern level.
Quaternary Period: 250 ppm CO2. Temp 0 C above modern level.
Then you get to the Modern Period. Frankly we are still living in an Ice Age.