Wood Romances

The Paleocene–Eocene Thermal Maximum (PETM) was a period of time beginning about  56 million years ago. Temperatures increased by 5–8°C[2][4] due to a large excursion of biogenic carbon. Temperatures increased extremely rapidly, and the perturbation of the carbon cycle led to ocean acidification and a mass extinction of benthic foraminifera. The warming event occurred suddenly, geologically speaking, perhaps in as little as 10,000 years[12], making it one the most rapid warming events detected in the Phanerozoic. The extreme warmth of the PETM lasted less than 220,000 years before returning to "normal" Eocene levels. The rapid warming warming associated with the PETM makes it a good analogue to current warming, so I think it would be helpful to cover this event as well as provide a bibliography for further reading on the subject. The PETM is also one among many examples in geologic history where it is clear that GHGs were driving global warming. CO2 led (and drove) the warmin...

In January, I blogged about a lecture I watched from Jessica Tierney, a geologist who has done some fascinating work in paleoclimate, in which she described the research behind a new paper that was at the time still undergoing peer review. You can watch the video and see my previous thoughts about this here . Ever since I watched this lecture, I have been anticipating the publication of the paper and hoping that the text wouldn't be behind a pay wall so I could learn more about what Tierney shared in her lecture. Well, late last week, both of my hopes became a reality. The paper is published and the full version is available. The lead author is Emily Judd[1], and this appears to be a remarkable paper. The tl;dr for this paper is that Emily Judd and her colleagues put together a data analysis (PhanDA) reconstruction of global temperatures and CO2 for the last 485 million years (most of the Phanerozoic), and they found that GMST varied greatly on geologic time scales, ranging from ...

Despite the common misconception that estimates for equilibrium climate sensitivity (ECS) are only derived from model simulations (sometimes erroneously said to be model inputs), there are many ways to estimate ECS. Here on this blog, I've used the energy balance equation with empirical data, and despite varying levels of complexity in quantifying forcings, I keep coming up with a value for ECS of ~3.2°C for 2xCO2 . I consider these back-of-the-envelope calculations, fitting for a blogpost to show IPCC estimates are plausible and realistic, but not really for much else. All these types of equations cover a relatively short time period (~175 years) and can be significantly impacted by the uncertainties in the relevant forcings, most importantly aerosols. Some recent evidence suggests that scientists may be underestimating the cooling effect of aerosol pollution and thus underestimating ECS. In fact, Hansen published a paper recently suggesting that ECS could be as high as 4.8°C.[1] ...

I watched a lecture recently with Dr. Jessica Tierney, who is a professor of geosciences at the University of Arizona. Her lecture was fascinating to me because she explains how reanalyses (what she calls Data Assimilation or DA) can be used to reconstruct past climates. The lecture also gives us a preview to an upcoming paper with Tierney as a co-author that reconstructs global temperatures over most of the Phanerozoic (almost 500 million years). The method they use is notable to me for it's use in  Osman's recent reconstruction for which Tierney is a co-author. I won't go into a lot of detail here, since she explains it in the above video, but essentially DA starts with  an ensemble of model simulations of past climates as a "prior." The model ensemble is spatially complete, but it isn't real - it's a simulation of what the past may have been like. DA then corrects the model results with proxy data. The proxy data has a huge advantage over models in tha...

Cenozoic CO2 and Temperature A new paper was published this month that I think will produce some exciting new insights for those interested in historical geology and paleoclimate studies. The paper is a product of the Cenozoic Carbon dioxide Proxy Integration Project (CenCO2PIP) Consortium, and it looks to reconstruct the proxy evidence for CO2 levels during the Cenozoic (the last 66 million years). The Cenozoic began after the asteroid impact (and/or volcanism) at the Cretaceous-Tertiary (K-T) boundary that caused the mass-extinction that included the extinction of non-avian dinosaurs. The value of this kind of work will have significant benefits for scientists as they seek to constrain estimates for long-term climate sensitivity (ESS). We can think of "sensitivity" on roughly three time scales:  TCR : On a near-immediate time scale, GMST increases with increasing CO2 in what is called transient climatic response (TCR), which generally speaking tells you how quickly temperat...