Climate Dynamics Fall 2017
All seminars at 1:30pm on Wednesday unless otherwise noted.
Check back for updates – titles and more speakers to be posted.
29 Nov: Brian Gross (NOAA-EMC)
Research Hall 163
6 Dec: George Philander (Princeton U.)
Research Hall 163
The Hedgehog and The Fox1
A Nelson Mandela Perspective on Global Warming
Global warming, a Tragedy of the Commons2 that requires “a fundamental extension in morality,” is polarizing because it poses both scientific and ethical challenges. How do we find a balance between our responsibilities to those living in abject poverty today, and our obligations to future generations? Science has no answer. To paraphrase Galileo: “science tells us how the heavens go, but not how to go to heaven”. The challenge is to bridge the cold, calculating, uncompromising world of science, and the profoundly different world of human affairs where compromise is a requisite, compassion a virtue. For guidance on how to proceed we can turn to Nelson Mandela, an authority on coping with polarized situations. The Clint Eastwood movie INVICTUS (about a rugby tournament in Johannesburg in 1995) provides part of his answer. The Kenny Rogers song “The Gambler” provides another. The solution is to know when to be a fox, when to be a hedgehog1. The seasonal cycle, the huge, annual global climate change that everyone experiences, is an excellent vehicle for exploring solutions to this dilemma.
1. Archilochus (7th-century b.c.e.): The fox knows many things, but the hedgehog knows one big thing.
2. Hardin G. Tragedy of the Commons Science vol 162, pp 1243-1248, 1968.
18 Dec: Current Climate Conversation
Mon 2:00 Research Hall 121 (note new date and time)
Earlier This Semester
11 Sep: Current Climate Conversation
Mon, 1:30pm, Research Hall 121
13 Sep: Jagadish Shukla (George Mason University)
Dynamical Seasonal Prediction: The Tale of Two ENSO-Monsoons and rainfall over India
Research Hall 163
After 50 years of climate modeling, and nearly 30 years after it was suggested that there is a scientific basis for dynamical seasonal prediction, the fidelity of climate models improved so that the models could produce a skillful prediction of Indian summer monsoon rainfall. The first part of this seminar will give a historical overview of monsoon forecasting, and a personal retrospective of the evolution of the science of dynamical seasonal prediction. The second part of the seminar will present the results of reforecasting summer monsoon rainfall in the past 57 years (1958-2014) using the NCEP Climate Forecast Systems. It will be shown that if the modern day coupled climate models were available during the 1970’s, even with the limited ocean observations at that time, it should have been possible to predict the 1972-73 ENSO event and the associated severe monsoon drought. This seminar will also present a comparison of the two strongest events – 1972-73 and 1997-98, for both of which ENSO was predicted quite accurately but the prediction of monsoon rainfall over India for 1997-98 was quite inaccurate.
20 Sep: Vikram Mehta (Center for Research on the Changing Earth System;CRCES)
Societal Impacts of Natural Decadal Climate Variability – Pacemakers of Civilizations
Exploratory Hall 3301
A substantial body of research has focused on understanding causes, mechanisms, and impacts of natural decadal climate variability (DCV) such as Pacific Decadal Oscillation (PDO), tropical Atlantic sea-surface temperature gradient variability (TAG), and decadal variability of El Niño-La Niña events. Tree-ring data going back more than 700 years show decadal hydrologic cycles (DHCs) associated with the rise and fall of civilizations, large-scale famines, and socio-political revolutions. Instrument-measured data confirm presence of DHCs. This talk, drawn from my recently-published book (Mehta, V.M., 2017: Natural Decadal Climate Variability: Societal Impacts), will give an overview of worldwide impacts of DCV phenomena, with specific examples of socio-economic-political impacts. The talk will end with an outline of actions needed to adapt to these impacts.
27 Sep: Kingtse Mo (Climate Prediction Center NOAA)
Drought Variability over the United States
Exploratory Hall 3301
We examined historic drought variability over the conterminous U.S. (CONUS) using observed precipitation (P) and reconstructed total moisture percentiles (TMP) and runoff from four land surface models over the period 1916-2013. We identified 16 drought events that covered more than 50% of the CONUS, most located at least partially over the Central U.S., which plays a critical role in U.S. (and global) food production. Most of these large droughts occurred when sea surface temperatures were cold in the tropical Pacific and warm in the North Atlantic. Droughts occurred less often and events were less severe as time progressed. In addition to long term trends, we found strong decadal variations in drought occurrence. Our analysis shows that U.S. droughts have preferred times of year for onset and demise. They are most likely to start in autumn (at the end of the rainy season) and end at the beginning of the spring rainy season.
4 Oct: Suki Manabe (Princeton U)
Interhemispheric Asymmetry in Global Warming
Research Hall 163
As the concentration of greenhouse gas increase in the atmosphere, temperature increases at the earth surface. In the Northern Hemisphere, the magnitude of the warming increases with increasing latitude and is at a maximum over the Arctic Ocean and its immediate vicinity. In the Southern Hemisphere, on the other hand, the polar amplification of the global warming is absent in the Antarctic Ocean. This is what happened in the numerical experiment conducted at GFDL almost 30 years ago.
The geographical pattern of global warming described above appears to be broadly consistent with the pattern of surface temperature change that have been observed during the last several decades, when the rate of increase of greenhouse gas is pronounced. In this talk, I would like to discuss the role of ocean in delaying global warming particularly in the circumpolar ocean of the Southern Hemisphere.
11 Oct: Current Climate Conversation
Research Hall 121
25 Oct: Bohar Singh (George Mason University)
Seasonality of the Tropical Intraseasonal Oscillations: Sensitivity to Mean Background State
10am, Research Hall 163
Tropical intraseasonal oscillations (TISO) are identified with anomalies of atmospheric convection with 20-100 day periods and large spatial scale. We find that TISO events propagate eastward from November to April and northward from May to October. A composite analysis of the mean background reveals that the co-occurrence of warm climatological SST and mean westerly wind plays an important role in setting the location and propagation direction of TISO. Sensitivity experiments indicate that the regionality and seasonality of TISO are closely coupled to the SST and the low-level circulation. The SST in the tropics must reach a required threshold for convection to occur, while the low-level circulation controls the direction of propagation by controlling the location of moisture convergence.
25 Oct: Paul Dirmeyer (George Mason University)
Land-Atmosphere Interactions in Nature and Models
Exploratory Hall 3301
Feedbacks in the water and energy cycles from the land surface to the atmosphere can provide a means to improve the prediction of weather and climate, as persistent anomalies in land surface states such as soil moisture can provide memory and signal beyond what the atmosphere alone can maintain. In this talk, I will present a brief history of notions of land-atmosphere feedbacks, culminating with the “breakthrough” finding of regional hot-spots (analogous to El Niño) of land-atmosphere interactions around the world. A description will be given of the evolution of the theory of land-atmosphere coupling, and how we are applying that theory along with newly-available observational data sets to validate our weather and climate models in new ways. I will conclude by showing evidence of predictability and enhanced prediction skill attributable to knowledge of land surface states.
18 Oct: Charles Ichoku (NASA Goddard Space Flight Center)
Understanding the Drivers of Water-Cycle Dynamics in Tropical sub-Saharan Africa
Exploratory Hall 3301
Parts of tropical sub-Saharan Africa north of the Equator have experienced multiple episodes of devastating droughts, but occasionally also intense flooding. Some of the phenomena to which this situation has been attributed include: large-scale natural variability such as the El-Nino southern oscillation (ENSO), remote industrial sulfur emissions, and regional grazing and biomass-burning activities. In this talk, we will examine how large scale natural phenomena such as ENSO and the Atlantic Multidecadal Oscillation (AMO) may have contributed to severe droughts during the 1970s and 1980s, as symbolized by the dramatic drying of Lake Chad. Secondly, we will examine changes in regional hydrological indicators, which are associated with satellite-observed land-use activities which utilize wildland fires and other types of biomass burning. Thirdly, we will examine the intrinsic precipitation patterns observed from satellite and ground-based measurements. Finally, we will provide some perspectives on future research that can help unravel some of the ambiguities related to the highly variable water-cycle dynamics in tropical sub-Saharan Africa.
1 Nov: John Cook (George Mason University)
Responding to alternative facts in a post-truth world
Research Hall 163
In recent times, we have seen an increased prevalence of fake news with the public seeming to rely less on scientific evidence. How should scientists respond to these concerning trends? Several decades of research into climate science denial offers insights into the post-truth phenomenon – which displays the same kind of motivated reasoning as those who reject the scientific consensus on climate change. This talk will examine the psychological research into science denial – why and how do some people reject science and how might we respond?
8 Nov: Current Climate Conversation
Research Hall 121 (returned to original date after recent change)
13 Nov: Elizabeth Barnes (Colorado State University)
Causal Links Between the Arctic and the Midlatitude Jet-streams
Mon, 1:30pm, Research Hall 163
The Arctic has been warming rapidly over the past few decades, raising the question of how polar warming may impact the weather in lower latitudes. Here, we apply causal discovery techniques (e.g. Granger causality) to quantify the sensitivity of the jet-streams to variations in Arctic temperatures on subseasonal timescales using 4800 years of CMIP5 model simulations. These causal discovery techniques allow us to quantify the jet-stream sensitivity in the presence of feedbacks, as well as assess seasonal and regional sensitivities. A further benefit of this approach is that we can make direct comparisons of the sensitivities between observations and models, as well as across many models, and here we demonstrate that model differences in the mean-state circulation can lead to differences in the jet-stream response to Arctic temperature variability. While this talk is focused on the causal links between Arctic warming and the midlatitude atmospheric circulation, we hope it also highlights the relevance and utility of causal discovery techniques for atmospheric dynamics research.
15 Nov: Joe Fiore (NWS)
NWS GOES-16 Operational Test and Evaluation (OT&E) Process & Overview
Wed, 11:00-12:00, Exploratory Hall 3301 [note corrected date]
An introduction to where our branch fits in the NWS, what our general OT&E (and life cycle model testing) process involves, then specifics about the GOES-16 OT&E .
15 Nov: Dwi Susanto (U Maryland College Park)
Overview of Indonesian Throughflow and its Role on Global Ocean Circulation and Climate
Exploratory Hall 3301
Indonesian Throughflow (ITF) is the leakage of western tropical Pacific water into the southeastern Indian Ocean through the narrow passages of Indonesian Seas. ITF is an important pathway for the transfer of climate signals around the world’s oceans. An overview of the ITF in the Makassar Strait will be presented with results and detailed transport estimates. The ITF branch through the South China Sea-Karimata Strait has received little observational attention until the SITE (South China Sea-Indonesian Transport/Exchange) field measurement program. Preliminary results from SITE will be described. The current logistical and financial challenges facing current field measurements are not sustainable in the long run and therefore other approaches such as numerical model, remotely sensed and paleoclimate data will be discussed.
The ocean absorbs a large portion of the anthropogenic heat released in the climate system, leading to an increase in global mean sea level rise. The magnitude, pattern and rate of ocean heat uptake are governed by several processes such as deep water formation, Southern Ocean Ekman pumping, and air-sea interaction. The spatial patterns of heat uptake and storage are further impacted by heat redistribution via changes in the ocean circulation, induced by natural variability and anthropogenic forcing.
We use observations, theory and a hierarchy of models to estimate the heat storage and thermosteric sea level rise in the Atlantic due to changes in circulation during the observational period and in future projections. We will show that about 2/3 of the thermosteric sea level rise at the latitude of NYC in the past 50 years is attributed to ocean circulation changes and traced back to surface forcing. We will further explore the link between air-sea forcing, ocean circulation and heat and carbon uptake in future projections. Our findings highlight high-latitude forcing as the cause for the large uncertainty in regional sea level projections, and provide a way forward to constrain regional projections of ocean heat uptake and sea level rise, including the use of anthropogenic carbon to infer circulation changes.
Fall 2017 Geology Seminar Series
Thursdays, 4:00-5:30, Exploratory Hall 1309
Sep 7 – Ron Martin, University of Delaware (history of biodiversity)
Sep 21 – Jesse Reimink, Carnegie Institution (earliest Earth terranes)
Special Public Lecture
Oct 5 – Howard Spero (U California – Davis)
Geosciences Frontier – Pursuing Novel Questions with 21st Century Tools
9:00-10:00am, Exploratory Hall 3301
About the Speaker: Prof. Spero is an AGU Emiliani Lecturer, and is a Fellow of AGU, AAAS, the Geological Society of America, and the California Academy of Sciences. His research focuses on the biological and environmental parameters that affect the stable isotope and trace metal geochemistry of the shells of recent and fossil organisms; paleoclimatology, marine micropaleontology, and paleoceanography.
Oct 5 – Daniel Viete, Johns Hopkins University (metamorphic petrology)
Oct 12 – Alan Pitts, University of Camerino (GMU’s new field camp)
Oct 19 – Ross Mitchell, Curtin University (supercontinent cycles)
Nov 2 – Marco Franceschi, Fulbright, Padua (ancient marine margin carbon sequestration)
Nov 16 – Rocio Caballero-Gill, USGS (Pliocene oceanography)
Nov 30 Note: seminar cancelled.
[Damien Pas, AOES-GMU (Devonian paleoclimates)]
7 Dec: ESS Master’s and AOES Scholars presentations