“Given how many unknowns (known and unknown) there are about “the recent ice ages” they really shouldn’t be “strongtly suggest[ing]” anything.”
They certainly suggest that a falling tree didn’t send the climate off on some wildly different path, but instead that it was still governed by major forcings and reasonably predictable.
Judith, in your link to Bjorn Stevens’ talk, the title has a typo: you reversed the inequalities; should be: “2.0 < ECS < 3.5"
Climate sensitivity is a convenient rule of thumb to describe a complex system.
It works best if there is a single dominant forcing
There is, greenhouse gases.
It just fits with 60 years of data and gives a lower estimate of ECS. This kind of data fit makes it unsurprising that 2 C would be a lower limit to ECS.
“Why is the assumption warranted?”
The Holocene suggests it. And it isn’t about the assumption being “warranted” — this paper isn’t making a prediction — it’s about making the assumption and seeing what its consequences are. Scientists do it every day, because it aids learning and understanding.
Heehee, single? And how dominant? You don’t know, and neither do all the king’s climatologists and all the king’s models.
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Produces a lot of Europe’s veg. The problem is that the people who work in them are exploited, working in 45 C heat for little money and exposure to a lot of nasty ag chemicals.
a falling tree didn’t send the climate off on some wildly different path, […]
Straw man.
Not much of anything at all that reduces risk.
The fossil carbon problem is effectively solved. We just have to wait for the answer to work itself out.
OTOH the risk to your socialist utopia…
“…so you can take the transient sensitivity as just a lower limit of ECS, which is its relevance to this discussion.”
No, because, again, the calculation doesn’t include long-term feedbacks (which are not all necessarily positive.) But the major point is that being unable to make an accounting of historical aerosols, which cool, the number is too unrealistic to mean anything.
David Appell — you recommend taking action, but no truly meaningful action is being contemplated. None of the steps taken or steps proposed will stop the atmospheric concentration of CO2 from continuing to rise. Since you’re worried about climate change, are you not furious at Obama and the EPA for trumpeting steps that are utterly inadequate? Their approach discourages other approaches that might have a chance of actually working.
U beat me 2 it. :)
So with those assumptions we’ve stopped the next glaciation. Good work, Humans. Your next mission, should you choose to accept it, is greening up the biome, despite its greatest efforts, abetted by the sun, to commit suicide by freezing and CO2 starvation. You’ve got your work cut out for you, Humans. I come in Peace.
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“RPC 2.6 is not close to what actually happened.”
RCP 2.6 means the radiative forcing is 2.6 in the year 2100 relative to the pre-industrial value, not that it’s been a constant 2.6 all along.
The end of this useless, non-scientific debate will be obvious when the most powerful leaders join together to lead the public in a prayer of gratitude to “the force of creation“ they could not hide.
See: “Teacher’s Supplement to Solar Energy”
A garden variety bump in a Holocene which is all bumps and dips. That’s all we had at the start of this “debate” and all we have now. The rest is shoddy artifice, from the studio which brought us Return to Almora.
From the abstract: “Assuming that ice growth mainly responds to insolation and CO2 forcing, this analogy suggests that the end of the current interglacial would occur within the next 1500 years, if atmospheric CO2 concentrations did not exceed 240±5 ppmv.”
Wow, such precision.
But what drives ice sheet ebb and flow is probably not just those two factors. See “Insolation-driven 100,000-year glacial cycles and hysteresis of ice-sheet volume”, Nature, 2013. The contribution of delayed isostatic adjustment (gradually changing high latitude surface height) appears key to the duration of glacial and interglacial epochs, the rapid rise out of glacial periods, and the slow descent into glacial periods. Ice core data shows the last interglacial ended with atmospheric CO2 still near 270 – 280 PPM. See: http://upload.wikimedia.org/wikipedia/commons/c/cd/Atmospheric_CO2_CH4_Degrees_Centigrade_Over_Time_by_Reg_Morrison.jpg There is no reason to think the same thing would not happen again. I agree that our descendents are not likely going to see another glacial period if atmospheric CO2 is above 400 PPM.
As Gavin Schmidt pointed out in reply to that comment, Nic Lewis attended the conference (as Judith notes in her post).
