4 ms·

This is good data, but I think "approaching" is doing a lot of heavy lifting in this title - more than is supported by the abstract: >>> Using an empirical mod

This is good data, but I think "approaching" is doing a lot of heavy lifting in this title - more than is supported by the abstract: >>> Using an empirical model incorporating these dynamics (validated with warming experiment data), we found that tropical forests can withstand up to a 3.9 ± 0.5 °C increase in air temperatures before a potential tipping point in metabolic function, but remaining uncertainty in the plasticity and range of Tcrit in tropical trees and the effect of leaf death on tree death could drastically change this prediction. 3.9 ± 0.5 °C is a lot of runway; likely moreso than we have with other ecosystems. This isn't good by any means, but significantly less dire than other threats.

jacquesm 3y ago
And when it's 45 degrees you'll be right there saying that there is nothing we can do about it now, so we should just accept it?
- belval 3y ago
  Pretty sure that what he's saying is that if we need a 4C increase to trigger mass die-off of tropical forests it's mostly irrelevant since at +4C we enter a lot of other catastrophic scenarios. It's like if you discovered that when your house is on fire the windows will break. It's interesting on the scientific merits but if your house is on fire the whole building is at stake so it was already understood that the windows will break.
  - sdenton4 3y ago
    To be sure, when it's mass die off of one of the planets major carbon sinks we're talking about, it's good to pay more attention to the low end of the confidence interval...
  - jacquesm 3y ago
    No, it's not that. It's that there are multiple factors that put those forests at risk and all of them need to be mitigated to the point that they are safe for the foreseeable future. Deforestation is a huge problem, but this temperature effect has the potential to kill off entire forests in one go. So even if it is a little bit over the horizon assuming that you are going to be able to save some of the forests you'll still lose them. So you need to have multiple lines of attack at once, otherwise you will fail.
- mentalpiracy 3y ago
  I plainly did not say that there was nothing to do about it, but I appreciate your enthusiastic defense of the forests. Unless we stop clear-cutting in the short term, there won't be any rainforests left by the time the temperatures hit 45C.
  - jacquesm 3y ago
    Both are a problem. The time to act is now not when the temperatures are so high that the trend alone + momentum will be enough to reach the point of no return. We really need those trees. So instead of trying to dismiss the article you could do a better job at making the case for action instead of pretending that there is 'plenty of room' when clearly there isn't. Because even in this comment you give another reason to say it's pointless and that we will hit 45 degrees. Clearcutting rainforest is a huge problem, bigger so because the rich countries arguing that the poor countries shouldn't be doing this after clearcutting their own land is hypocritical to the extreme. But rising temperatures are by themselves also a huge problem and this is an 'either/or' situation, which means we need to tackle all of these in ways that last.
    - mentalpiracy 3y ago
      Genuine question: would you please quote where I dismissed the entire study? (note that I have slightly modified the wording of the first sentence since your original reply - the original phrasing was: >>> "approaching" is doing a lot of heavy lifting in this title - far more than is supported by the abstract (imo) ) I was critical of a single word in the title.
      - jacquesm 3y ago
        That's exactly the problem though: rather than to build upon the ideas in the article all you did was find fault with a single word, and that drove your comment. Instead, if you were to take this serious you could approach it constructively rather than destructively. It's maybe a bit more work but I think the cumulative effect of that would result in a much better discussion around the subject matter. 6 degrees difference sounds like it is huge, right? But: that's 6 degrees with a margin of error, and with a difference per species (it is an average!) that further enlarges that margin for error. Then there are possible feedback mechanisms to contend with, as well as various local effects. Rather than to just accentuate the fact that 'approaching' is doing the heavy lifting it would be trivial to point out that this is how scientists communicate around things they are not 100% sure of (and that includes most things), but meanwhile us silly laypeople should not assume that because the statement is made carefully that it still is a warning and so can't be dismissed out of hand. That is more typing but it takes you out of 'dismissal', which is how I read your original comment, especially with the 'far more' in there which is - ironically - doing a lot of heavy lifting in your original comment.
hedora 3y ago
Yeah; by the time we are at 3.4C (the bottom of that range), we're already to the point where a large percentage of people are climate refugees. In addition to many currently-inhabited places being too hot for humans to survive, the Atlantic current will have already collapsed, so bug chunks of Western Europe will probably be under a glacier.
- landemva 3y ago
  USGS has a decent and short write-up of glaciers across Europe. It says 20,000+ years ago. https://www.usgs.gov/media/images/glaciers-extended-over-much-europe-during-last-ice-age https://www.usgs.gov/media/images/glaciers-extended-over-muc...
  - hedora 3y ago
    Yeah; crucially, we have some fossil record of the run up to that glacier, with 50 year resolution: Sample 1: Normal Sample 2: Atmospheric CO2 spike. Sample 3: Glacier Based on that, we are 0-75 years away from the next European ice age, which the maximum expectation estimate at ~25 years.
Retric 3y ago
It’s not 4C when there’s this much uncertainty involved. The concern isn’t hitting X temperature and everything instantly fails it’s looking for the lowest temperature where positive feedback loop occurs. That feedback temperature might be 3.4C or it might be 0.4C, this study hasn’t discovered a specific answer just a very critical threshold we are fairly close to where bad stuff occurs. “Leaf thermocouple data from multiple sites across the tropics suggest that even within pixels of moderate temperatures, upper canopy leaves exceed Tcrit 0.01% of the time.” So it’s a rare event right now. Perhaps at +0.8C such extreme events become common enough for large local die offs to occur. When coupled with tree lifespan you actually get widespread cumulative damage much sooner than expected. Or perhaps it’s not a problem, we don’t have a definitive answer just one study.

jacquesm 3y ago

And when it's 45 degrees you'll be right there saying that there is nothing we can do about it now, so we should just accept it?

belval 3y ago
Pretty sure that what he's saying is that if we need a 4C increase to trigger mass die-off of tropical forests it's mostly irrelevant since at +4C we enter a lot of other catastrophic scenarios. It's like if you discovered that when your house is on fire the windows will break. It's interesting on the scientific merits but if your house is on fire the whole building is at stake so it was already understood that the windows will break.
- sdenton4 3y ago
  To be sure, when it's mass die off of one of the planets major carbon sinks we're talking about, it's good to pay more attention to the low end of the confidence interval...
- jacquesm 3y ago
  No, it's not that. It's that there are multiple factors that put those forests at risk and all of them need to be mitigated to the point that they are safe for the foreseeable future. Deforestation is a huge problem, but this temperature effect has the potential to kill off entire forests in one go. So even if it is a little bit over the horizon assuming that you are going to be able to save some of the forests you'll still lose them. So you need to have multiple lines of attack at once, otherwise you will fail.
mentalpiracy 3y ago
I plainly did not say that there was nothing to do about it, but I appreciate your enthusiastic defense of the forests. Unless we stop clear-cutting in the short term, there won't be any rainforests left by the time the temperatures hit 45C.
- jacquesm 3y ago
  Both are a problem. The time to act is now not when the temperatures are so high that the trend alone + momentum will be enough to reach the point of no return. We really need those trees. So instead of trying to dismiss the article you could do a better job at making the case for action instead of pretending that there is 'plenty of room' when clearly there isn't. Because even in this comment you give another reason to say it's pointless and that we will hit 45 degrees. Clearcutting rainforest is a huge problem, bigger so because the rich countries arguing that the poor countries shouldn't be doing this after clearcutting their own land is hypocritical to the extreme. But rising temperatures are by themselves also a huge problem and this is an 'either/or' situation, which means we need to tackle all of these in ways that last.
  - mentalpiracy 3y ago
    Genuine question: would you please quote where I dismissed the entire study? (note that I have slightly modified the wording of the first sentence since your original reply - the original phrasing was: >>> "approaching" is doing a lot of heavy lifting in this title - far more than is supported by the abstract (imo) ) I was critical of a single word in the title.
    - jacquesm 3y ago
      That's exactly the problem though: rather than to build upon the ideas in the article all you did was find fault with a single word, and that drove your comment. Instead, if you were to take this serious you could approach it constructively rather than destructively. It's maybe a bit more work but I think the cumulative effect of that would result in a much better discussion around the subject matter. 6 degrees difference sounds like it is huge, right? But: that's 6 degrees with a margin of error, and with a difference per species (it is an average!) that further enlarges that margin for error. Then there are possible feedback mechanisms to contend with, as well as various local effects. Rather than to just accentuate the fact that 'approaching' is doing the heavy lifting it would be trivial to point out that this is how scientists communicate around things they are not 100% sure of (and that includes most things), but meanwhile us silly laypeople should not assume that because the statement is made carefully that it still is a warning and so can't be dismissed out of hand. That is more typing but it takes you out of 'dismissal', which is how I read your original comment, especially with the 'far more' in there which is - ironically - doing a lot of heavy lifting in your original comment.

hedora 3y ago

Yeah; by the time we are at 3.4C (the bottom of that range), we're already to the point where a large percentage of people are climate refugees. In addition to many currently-inhabited places being too hot for humans to survive, the Atlantic current will have already collapsed, so bug chunks of Western Europe will probably be under a glacier.

landemva 3y ago
USGS has a decent and short write-up of glaciers across Europe. It says 20,000+ years ago. https://www.usgs.gov/media/images/glaciers-extended-over-much-europe-during-last-ice-age https://www.usgs.gov/media/images/glaciers-extended-over-muc...
- hedora 3y ago
  Yeah; crucially, we have some fossil record of the run up to that glacier, with 50 year resolution: Sample 1: Normal Sample 2: Atmospheric CO2 spike. Sample 3: Glacier Based on that, we are 0-75 years away from the next European ice age, which the maximum expectation estimate at ~25 years.

Retric 3y ago

It’s not 4C when there’s this much uncertainty involved. The concern isn’t hitting X temperature and everything instantly fails it’s looking for the lowest temperature where positive feedback loop occurs. That feedback temperature might be 3.4C or it might be 0.4C, this study hasn’t discovered a specific answer just a very critical threshold we are fairly close to where bad stuff occurs. “Leaf thermocouple data from multiple sites across the tropics suggest that even within pixels of moderate temperatures, upper canopy leaves exceed Tcrit 0.01% of the time.” So it’s a rare event right now. Perhaps at +0.8C such extreme events become common enough for large local die offs to occur. When coupled with tree lifespan you actually get widespread cumulative damage much sooner than expected. Or perhaps it’s not a problem, we don’t have a definitive answer just one study.