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Global heating has already happened, we’re 1C up on preindustrial. The question is how high are we willing to go. Doing nothing will lead to another 6C, concert

Global heating has already happened, we’re 1C up on preindustrial. The question is how high are we willing to go. Doing nothing will lead to another 6C, concerted serious action will be another 2C, and we could end up anywhere in between, depending on what and whether tipping points exist, as well as people’s good sense, and their willingness to elect politicians who will do something.

esotericn 7y ago
> Doing nothing will lead to another 6C Surely doing nothing (not actually doing nothing, but rather continuing to burn fossil fuels) leads to, well, ~ infinite warming until we run out of fuel? Or is the assumption that at 6c we're dead so whatever?
- Brakenshire 7y ago
  Without big feedback loops you actually have to go out of your way to get above a certain level of warming. RCP8.5, for 8.5C of warming, involves a frankly silly quantity of emissions, I assume this is because CO2 absorbs at certain wavelengths and there are diminishing returns as concentrations get really high. Of course, we don’t know what the feedback loops are, they could kick in and take over. The IPCC is quite conservative about including feedback loops, and mainly deals with direct effects. But the same logic applies either way, within any reasonable range any reduction in CO2 emissions is worth pursuing. I also personally think the economics for certain low carbon technologies will dominate over a middle/long time period, just that as it stands they won’t take over quick enough to dramatically bring down emissions.
  - hire_charts 7y ago
    What kinds of feedback loops is the IPCC known to exclude, and is there any serious study into what the potential consequences are? Like, how possible is it that there is a feedback loop that will push us well beyond the RCP8.5 scenario?
    - Brakenshire 7y ago
      Two examples I recall are the albedo changes from melting of on-land glaciers and ice-sheets, the IPCC thinks think will take hundreds of years. And then the Methane Clathrate idea, which is very controversial but could contribute to some degree. I don’t think anyone in the world can answer the question about how likely these feedback effects are, unfortunately!

esotericn 7y ago

> Doing nothing will lead to another 6C Surely doing nothing (not actually doing nothing, but rather continuing to burn fossil fuels) leads to, well, ~ infinite warming until we run out of fuel? Or is the assumption that at 6c we're dead so whatever?

Brakenshire 7y ago
Without big feedback loops you actually have to go out of your way to get above a certain level of warming. RCP8.5, for 8.5C of warming, involves a frankly silly quantity of emissions, I assume this is because CO2 absorbs at certain wavelengths and there are diminishing returns as concentrations get really high. Of course, we don’t know what the feedback loops are, they could kick in and take over. The IPCC is quite conservative about including feedback loops, and mainly deals with direct effects. But the same logic applies either way, within any reasonable range any reduction in CO2 emissions is worth pursuing. I also personally think the economics for certain low carbon technologies will dominate over a middle/long time period, just that as it stands they won’t take over quick enough to dramatically bring down emissions.
- hire_charts 7y ago
  What kinds of feedback loops is the IPCC known to exclude, and is there any serious study into what the potential consequences are? Like, how possible is it that there is a feedback loop that will push us well beyond the RCP8.5 scenario?
  - Brakenshire 7y ago
    Two examples I recall are the albedo changes from melting of on-land glaciers and ice-sheets, the IPCC thinks think will take hundreds of years. And then the Methane Clathrate idea, which is very controversial but could contribute to some degree. I don’t think anyone in the world can answer the question about how likely these feedback effects are, unfortunately!