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.

Comments

FFS the scaremongering is getting ridiculous

[Anonymous Coward]

Is pollution bad?

Yes.

Is global warming/climate change bad?

Yes.

Is human activity making climate worse?

Yes.

Is all the over-the-top scaremongering making it ridiculous?

Yes.

IT'S NOT GOING TO BE THE END OF THE FUCKING WORLD

CO2 levels over geologic time spans are usually much, much higher on Earth than the current 400 ppm. Levels in the thousands PPM are more normal.

For fuck's sake, the scaremongering just plays into denialist hands: "World will end in 12 years!" is straight from a religious nutter. It's just missing the "Repent!"

Re:FFS the scaremongering is getting ridiculous

[Immerman]

Over geological timescales, yes. Not during an icehouse glacial/interglacial period like we've been in for the entire history of the human species though. Warm things up dramatically, and we'll likely toggle to the planets hothouse state where such CO2 levels *are* fairly normal.

Once we get there, it might not be that bad - though the climate seems to have been a lot less stable in that state, with CO2 levels varying wildly, ecosystems changing frequently, and vast continent-spanning deserts not exactly being super rare. And even if we luck into tropics extending into Canada - the tropics are generally not actually considered a lovely place to live full time. The diseases alone put a damper on things.

A more immediate problem is the transition period, which tends to be a really traumatic event, with 90+% global extinction rates. Consider that an old-growth forest can't migrate very quickly, and when the trees go, so do most of the species that live there. And moving further from the equator chasing your optimal average temperature, also subjects you to more dramatic seasons. The Amazon Rainforest evolved to deal with a few degrees of seasonal variation - even if it could migrate to North America chasing the right average temperature, the seasons would kill most of it.

For a whole lot of species it *will* be the end of the world, and that's going to be really rough for us, perched on top of a global ecosystem that's already quite shaky from human-caused pollution and extinctions.

Re:FFS the scaremongering is getting ridiculous

[dasunt]

IT'S NOT GOING TO BE THE END OF THE FUCKING WORLD

No. But it will be expensive and disruptive.

Sooner or later we're going to need to pick out what places we'll try to save, and what places aren't worth saving. For the places we are going to try to save, we'll have to invest in infrastructure to mitigate some of the effects of climate change. For the places we aren't going to try to save, individuals can either try to survive with what they have, or move. If they survive, they'll have to invest and make changes in their lifestyle - such as limiting water usage and trucking in water if they are in an area where drought has caused water tables to fall, to raising their houses by the coast in order to survive hurricanes and king tides.

Re:Yet Another Doomsday Prediction

[XXongo]

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.

Not even a prediction

[XXongo]

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."

Scott adams climate challenge

[Okian Warrior]

If anyone's interested, Scott Adams (of Dilbert fame) is running a Climate change debate on his blog, where he invites believers and skeptics to post their best arguments with evidence, and he (as an intelligent person with no background) sorts through the bullshit for us.

One outcome of that debate is that claims of sea levels rising are bullshit. That's a concrete point, one where "the debate is settled" can now be applied. Sea levels have not risen to any appreciable degree, and that point cannot be made to show that climate change is real.

(They may rise in the future, but that is not the same as using *current* sea level changes as an argument for climate change.)

I look forward to Scott examining - one by one - all scientific claims of the climate change debate. Perhaps eventually we will arrive at a position everyone can agree on.

Re:Experiment Already Done and..NO

[Anonymous Coward]

Bullshit responses like that are why people become climate skeptics. Solar output was not 30% lower in any of the periods that OP showed. Solar output was much lower when the earth formed but was constant through all of those periods. So are you telling half truths through ignorance? Or are you deliberately trying to obscure the truth?