ckoven.bsky.social
Climate and carbon cycle scientist. I help make computer models of the biosphere and experiment on them so that we don't have to on the real one.
https://scholar.google.com/citations?user=fB5Lnz4AAAAJ
79 posts
1,687 followers
489 following
Regular Contributor
Active Commenter
comment in response to
post
URL gives a 404 error--not that I looked ;)
comment in response to
post
Congrats, great news!
comment in response to
post
ok cool, I thought it was just me that had to do that.
comment in response to
post
I feel like they are just like miniature starlings?
comment in response to
post
Me too! Waiting to hear back from @inaturalist.bsky.social on that. Will update if there is a consensus there.
comment in response to
post
we should write an op ed
comment in response to
post
Is there a word for the fear and hatred of wetlands, and if not, shouldn’t there be one, so that we can label it when we see it? Paludiphobia?
comment in response to
post
Cool! Is this free-running or data assimilation?
comment in response to
post
doh! typo in this. it should read, "if the temperature-to-cumulative-emissions relationship were perfectly path independent..."
comment in response to
post
These flat10MIP experiments are a really simple way to measure and compare all of these different coupled carbon-climate sensitivity metrics. Really excited to see this manuscript out, and looking forward to further use of these experiments in CMIP7!
comment in response to
post
Another key implication is for overshoot: the asymmetry in the global temperature response to negative emissions, on the scale required for overshoot scenarios, is basically already present even under zero emissions with no overshoot. So the key thing is to get to zero emissions as fast as possible.
comment in response to
post
The answer is that the models do show path dependencies, and they are all correlated, but the correlation weakens on longer timescales. So, for example, globally, temperature would stop rising anywhere from decades before to decades after net zero, and the timing is closely correlated with ZEC.
comment in response to
post
Like ZEC, if the warming-to-cumulative-emissions relationship were exactly path-independent, then each of these would be exactly zero. So any nonzero value is a measure of path dependence. Using the flat10MIP experiments, we can compare all of these metrics, to see how they relate to each other.
comment in response to
post
We can try to estimate some of these potential path dependencies using metrics derived from the flat10MIP experiments. So, in addition to ZEC, we quantified a set of other path dependencies using the experiment where emissions gradually go through net zero, all the way back to cumulative net zero.
comment in response to
post
Or what about the response to negative emissions? Some day, future generations might try to clean up the mess we have left, by pulling CO2 out of the air and storing it somewhere. How would the climate respond to that? Would it follow the same proportionality to cumulative emissions backwards?
comment in response to
post
But ZEC isn't the only potential path dependency that we might care about. For example, when, if we reduce emissions and achieve net zero, would we expect warming to stop? Al Gore focused on this point at the end of a recent TED talk.
comment in response to
post
Our best estimate of ZEC is that it is roughly zero, which aligns with path independence. I.e. if the temperature-to-cumulative-emissions relationship were perfectly path dependent, then it would follow that ZEC must be exactly zero.
comment in response to
post
But we don't have a strong handle on exactly how path-independent this relationship is. One way of estimating it is via something that we call the Zero Emissions Commitment, or ZEC, which we can measure in Earth System models by abruptly stopping CO2 emissions and looking at how warming responds.
comment in response to
post
One of the most basic relationships that informs climate policy is that global warming is proportional to cumulative CO2 emissions. The key thing about this relationship is its path independence, which implies that warming should respond both instantaneously and permanently to CO2 emissions.
comment in response to
post
Would love to hear the SPM plenary discussion on that.
comment in response to
post
Yeah that was the oddest thing about that exchange yesterday. IPCC AR6 assessed that ZEC has a range of 0 +/- 0.3 deg C. So if we are lucky and ZEC turns out to be negative, then net zero implies cooling rather than stabilization. IPCC, in its role as honest broker, already made the essential point.