Events

DeFord Lecture | Dr. Karen McKinnon

April, 24 2025

Time: 4:00 PM - 5:00 PM
Location: Boyd Auditorium (JGB 2.324)

Another record-breaking heatwave? Understanding the trends and drivers of heat extremes by Dr. Karen McKinnon, University of California Los Angeles

Abstract: Heat extremes result from the convergence of atmospheric and land processes across multiple spatial and temporal scales. While we can be quite confident that heat extremes will become more frequent in a warming world, major uncertainties remain in terms of how and why they will change. A recent notable example was the 2021 Pacific Northwest heatwave, which was so extreme that researchers initially struggled to put a nonzero probability on it. Using both in situ observations and a large climate model (CESM2) ensemble, we find that record-smashing extremes are much more likely to occur in regions like the Pacific Northwest that have climatologically positively skewed temperatures, which reflect the existence of processes that converge to cause very large extremes. As a result, the event was consistent with a human-caused warming of the mean combined with a low-probability sampling of an extreme weather pattern. More broadly, do we find evidence in the observational record that summertime extremes are warming faster than typical summertime temperatures? Despite the many recent high-impact heat waves around the world, we find that observations and climate models agree that the hottest summer temperatures have warmed at the same pace as the median from 1959-2023, although the coldest summer temperatures have warmed more slowly. The trends in the extremes compared to the median can be predicted from an equation derived from the surface energy balance, and are due to changes in surface radiative heating, and the fraction of heat that goes into evaporating water, on extreme versus typical days. Finally, we show that, in contrast to the general expectation of humidity increasing in a warmer climate, humidity has been decreasing on hot days across the semiarid subtropics, with concerning implications for fire risk. In the US Southwest, we trace the decrease to declining soil moisture and evapotranspiration, indicating an important land surface control on humidity trends. Collectively, the results provide a framework for understanding the probability of very unusual events in the relatively short observational record, and highlight the important role of energy partitioning at the surface for both heat and humidity trends.

UTIG Seminar Series: Jud Partin, UTIG

April, 25 2025

Time: 10:30 AM - 11:30 AM
Location: PRC 196/ROC 1.603

Speaker: Jud Partin, University of Texas Institute for Geophysics

Host: Yuko Okumura

Title: Back to the Future: Ancient El Niño events in a Warming World

Abstract: Extreme El Niños are hazardous events that caused widespread damage in the latter half of the 20th century, and we do not know how they will respond to anthropogenic warming. Models project a range of responses of the El Niño-Southern Oscillation (ENSO) strength to dramatic 21st-century increases in atmospheric CO2 – from a 50% increase, to no change, to a 50% decrease. Our approach to address the uncertainty of future extreme El Niño event projections is to examine how ENSO and extreme events respond to changes in background climate states different from today in both models and paleoclimate proxies. Past changes in ENSO act as an out-of-sample test for the emergent constraints of future ENSO strength and extreme El Niño frequency. However, the brevity of observations and the scarcity of tropical Pacific paleoclimate data coverage prior to 1960 leads to uncertainties in quantifying past ENSO variability.

Here, I present new deglacial and Holocene coral oxygen isotope records from Vanuatu and compare them with previously published coral data and new climate model simulations to analyze ENSO response to external forcings over the last 15,000 years. The coral records from the last ice age are unique, as most old coral archives of past El Niños were flooded in the rise of sea level during the last deglaciation. Using an ultra-portable drill our group designed and built, we recovered ice age corals from a rapidly uplifting island in Vanuatu that brought these ancient corals to the near surface. Using the Community Earth System Model V1, a model that projects more extreme El Niño events under anthropogenic forcing, I show that both the simulations and coral records exhibit a decrease in ENSO strength and extreme El Niño frequency 12 and 15 thousand years ago during the last deglaciation relative to modern times. Contrasts between past and future changes in simulated ENSO suggest exacerbated impacts of extreme El Niño events across the tropical Pacific in a warming world, pointing towards a future with higher socioeconomic losses due to these hazardous events.

Bureau of Economic Geology Seminar Series

April, 29 2025

Time: 10:00 AM - 11:00 AM

Bureau of Economic Geology Seminar Series

May, 06 2025

Time: 10:00 AM - 11:00 AM

Bureau of Economic Geology Seminar Series

May, 13 2025

Time: 10:00 AM - 11:00 AM