The Silurian Hypothesis: Would It Be Possible to Detect an Industrial Civilization in the Geological Record?

If an industrial civilization had existed on Earth many millions of years prior to ourown era, what traces would it have left and would they be detectable today? We summarize the likely geological fingerprint of the Anthropocene, and demonstrate that while clear, it will not differ greatly in many respects from other known events in the geological record. We then propose tests that could plausibly distinguish an industrial cause from an otherwise naturally occurring climate event

Discussion of: A statistical analysis of multiple temperature proxies: Are reconstructions of surface temperatures over the last 1000 years reliable?

Discussion of "A statistical analysis of multiple temperature proxies: Are reconstructions of surface temperatures over the last 1000 years reliable?" by B.B. McShane and A.J. Wyner [arXiv:1104.4002]Comment: Published in at http://dx.doi.org/10.1214/10-AOAS398F the Annals of Applied Statistics (http://www.imstat.org/aoas/) by the Institute of Mathematical Statistics (http://www.imstat.org

Climate Change: On Scientists and Advocacy

Last year, I asked a crowd of a few hundred geoscientists from around the world what positions related to climate science and policy they would be comfortable publicly advocating. I presented a list of recommendations that included increased research funding, greater resources for education, and specific emission reduction technologies. In almost every case, a majority of the audience felt comfortable arguing for them. The only clear exceptions were related to geo-engineering research and nuclear power. I had queried the researchers because the relationship between science and advocacy is marked by many assumptions and little clarity. This despite the fact that the basic question of how scientists can be responsible advocates on issues related to their expertise has been discussed for decades most notably in the case of climate change by the late Stephen Schneider

Early Pleistocene Obliquity‐Scale pCO2 Variability at ~1.5 Million Years Ago

In the early Pleistocene, global temperature cycles predominantly varied with ~41‐kyr (obliquity‐scale) periodicity. Atmospheric greenhouse gas concentrations likely played a role in these climate cycles; marine sediments provide an indirect geochemical means to estimate early Pleistocene CO2. Here we present a boron isotope‐based record of continuous high‐resolution surface ocean pH and inferred atmospheric CO2 changes. Our results show that, within a window of time in the early Pleistocene (1.38–1.54 Ma), pCO2 varied with obliquity, confirming that, analogous to late Pleistocene conditions, the carbon cycle and climate covaried at ~1.5 Ma. Pairing the reconstructed early Pleistocene pCO2 amplitude (92 ± 13 μatm) with a comparably smaller global surface temperature glacial/interglacial amplitude (3.0 ± 0.5 K) yields a surface temperature change to CO2 radiative forcing ratio of S[CO2]~0.75 (±0.5) °C−1·W−1·m−2, as compared to the late Pleistocene S[CO2] value of ~1.75 (±0.6) °C−1·W−1·m−2. This direct comparison of pCO2 and temperature implicitly incorporates the large ice sheet forcing as an internal feedback and is not directly applicable to future warming. We evaluate this result with a simple climate model and show that the presumably thinner, though extensive, northern hemisphere ice sheets would increase surface temperature sensitivity to radiative forcing. Thus, the mechanism to dampen actual temperature variability in the early Pleistocene more likely lies with Southern Ocean circulation dynamics or antiphase hemispheric forcing. We also compile this new carbon dioxide record with published Plio‐Pleistocene δ11B records using consistent boundary conditions and explore potential reasons for the discrepancy between Pliocene pCO2 based on different planktic foraminifera.Key PointsEarly Pleistocene pCO2 roughly varied with obliquity cyclesInterglacial pCO2 was similar in the early and late Pleistocene; glacial pCO2 declined over the mid‐Pleistocene transitionDiscrepancies between δ11B values and corresponding pCO2 estimates from G. ruber and T. sacculifer are observed and may indicate evolving vital effectsPeer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/147130/1/palo20675-sup-0004-2018PA003349-S03.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/147130/2/palo20675.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/147130/3/palo20675-sup-0002-2018PA003349-S01.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/147130/4/palo20675_am.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/147130/5/palo20675-sup-0005-2018PA003349-S04.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/147130/6/palo20675-sup-0003-2018PA003349-S02.pd

Scientific Advocacy: A Tool for Assessing the Risks of Engagement

Scientists active in the public sphere recognize the importance of broader communications but sometimes have an incomplete or exaggerated view of the risks to both their public and professional reputations as a function of their advocacy. These risks are connected fundamentally to the degree that the advocacy positions they take are based on values that are shared (or not) with their audiences. An encapsulation of the connections between Risks, Advocacy, and Values in Engagement (RAVE) may help inform choices that public scientists must make

Climate Informatics: Accelerating Discovering in Climate Science with Machine Learning

The goal of climate informatics, an emerging discipline, is to inspire collaboration between climate scientists and data scientists, in order to develop tools to analyze complex and ever-growing amounts of observed and simulated climate data, and thereby bridge the gap between data and understanding. Here, recent climate informatics work is presented, along with details of some of the field's remaining challenges. Given the impact of climate change, understanding the climate system is an international priority. The goal of climate informatics is to inspire collaboration between climate scientists and data scientists, in order to develop tools to analyze complex and ever-growing amounts of observed and simulated climate data, and thereby bridge the gap between data and understanding. Here, recent climate informatics work is presented, along with details of some of the remaining challenges

Flavor and Quark Mass Dependence of QCD Thermodynamics

We calculate the transition temperature in 2 and 3-flavor QCD using improved gauge and staggered fermion actions on lattices with temporal extent Nt=4. We find Tc=173(8)MeV and 154(8)MeV for nf=2 and 3, respectively. In the case of 3-flavor QCD we present evidence that the chiral critical point, i.e. the second order endpoint of the line of first order chiral phase transitions, belongs to the universality class of the 3d Ising model.Comment: Talk given at Lattice 2000 (Finite Temperature), 4 pages, 6 EPS-figure

Reconciling Warming Trends

Climate models projected stronger warming over the past 15 years than has been seen in observations. Conspiring factors of errors in volcanic and solar inputs, representations of aerosols, and El NiNo evolution, may explain most of the discrepancy

Evaluating the performance of past climate model projections

Author Posting. © American Geophysical Union, 2020. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Geophysical Research Letters 47(1), (2020): e2019GL085378, doi:10.1029/2019GL085378.Retrospectively comparing future model projections to observations provides a robust and independent test of model skill. Here we analyze the performance of climate models published between 1970 and 2007 in projecting future global mean surface temperature (GMST) changes. Models are compared to observations based on both the change in GMST over time and the change in GMST over the change in external forcing. The latter approach accounts for mismatches in model forcings, a potential source of error in model projections independent of the accuracy of model physics. We find that climate models published over the past five decades were skillful in predicting subsequent GMST changes, with most models examined showing warming consistent with observations, particularly when mismatches between model‐projected and observationally estimated forcings were taken into account.Z. H. conceived the project, Z. H. and H. F. D. created the figures, and Z. H., H. F. D., T. A., and G. S. helped gather data and wrote the article text. A public GitHub repository with code used to analyze the data and generate figures and csv files containing the data shown in the figures is available online (https://github.com/hausfath/OldModels). Additional information on the code and data used in the analysis can be found in the supporting information. We would like to thank Piers Forster for providing the ensemble of observationally‐informed radiative forcing estimates. No dedicated funding from any of the authors supported this project.2020-06-0