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1. Tropical Cyclones Downscaled from Simulations of the Last Glacial Maximum

   https://doi.org/10.1175/JCLI-D-20-0409.1  

   Lawton, Quinton A.; Korty, Robert L.; Zamora, Ryan A. (January 2021, Journal of Climate)

   null (Ed.)

   Abstract The tracks, intensities, and other properties of tropical cyclones downscaled from three models’ simulations of the Last Glacial Maximum (LGM) are analyzed and compared to those of storms downscaled from simulations of the present climate. Globally, the mean maximum intensity of storms generated from each model is lower at LGM, as is the fraction of all storms that reach intensities of category 4 or higher on the Saffir–Simpson hurricane wind scale. The median day of the storm season shifts earlier by an average of one week in all three models in both hemispheres. Two of the three models’ LGM simulations feature a reduction in storm count and global power dissipation index compared to the current climate, but a third shows no significant difference between the two climates. Although each model is forced by the same global changes, differences in the way sea surface temperatures and other large-scale environmental conditions respond in the North Atlantic impart significant differences in the climatology at LGM between models. Our results from the cold LGM provide a novel opportunity to assess how tropical cyclones respond to climate changes. 

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2. Atmospheric methane variability through the Last Glacial Maximum and deglaciation mainly controlled by tropical sources

   https://doi.org/10.1038/s41561-023-01332-x  

   Riddell-Young, Ben; Rosen, Julia; Brook, Edward; Buizert, Christo; Martin, Kaden; Lee, James; Edwards, Jon; Mühl, Michaela; Schmitt, Jochen; Fischer, Hubertus; et al (December 2023, Nature Geoscience)
3. Stratospheric Ozone in the Last Glacial Maximum

   https://doi.org/10.1029/2020JD032929  

   Wang, Mingcheng; Fu, Qiang; Solomon, Susan; White, Rachel H.; Alexander, Becky (November 2020, Journal of Geophysical Research: Atmospheres)

   Abstract Using the Whole Atmosphere Community Climate Model version 6, stratospheric ozone in the Last Glacial Maximum (LGM) is investigated. It is shown that, compared with preindustrial (PI) times, LGM modeled stratospheric temperatures are increased by up to 8 K, leading to faster ozone destruction rates for gas phase reactions, especially via the Chapman mechanism. On the other hand, stratospheric hydroxyl radical (OH) and nitrogen oxides (NO_x) concentrations are decreased by 10–20%, which decreases catalytic ozone destruction, thereby decreasing ozone loss rates. The net effect of these two compensating mechanisms in the upper stratosphere (above 15 hPa) is a vertically integrated 1–3 Dobson unit (DU) decrease during the LGM. In the lower stratosphere (tropopause to 15 hPa), changes in the stratospheric overturning circulation and resulting transport dominate changes in ozone. Consistent with a weakening of the residual circulation in the LGM, lower stratospheric ozone is increased by 2–5 DU in the tropics and decreased by 5–10 DU in the extratropics, but the latter is partly compensated by ozone increases due to a lower tropopause. It is found that tropospheric ozone is decreased by about 5 DU in the LGM versus PI. Combined changes in stratospheric and tropospheric ozone lead to a decrease in total ozone column everywhere except over the northeast North America, equatorial Indian and West Pacific Oceans. Surface ultraviolet radiation in the LGM versus PI is increased over the Northern Hemisphere middle and high latitudes, especially over the ice caps, and over the Southern Hemisphere near 60°S. 

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4. The Brewer‐Dobson Circulation During the Last Glacial Maximum

   https://doi.org/10.1029/2019GL086271  

   Fu, Qiang; White, Rachel H.; Wang, Mingcheng; Alexander, Becky; Solomon, Susan; Gettelman, Andrew; Battisti, David S.; Lin, Pu (February 2020, Geophysical Research Letters)

   Abstract The Brewer‐Dobson circulation during the Last Glacial Maximum (LGM) is investigated in simulations using the Whole Atmosphere Community Climate Model version 6. We examine vertical mass fluxes, age of stratospheric air, and the transformed Eulerian mean stream function and find that the modeled annual‐mean Brewer‐Dobson circulation during the LGM is almost everywhere slower than that in the modern climate (with or without anthropogenic ozone depleting substances). Compared to the modern climate, the annual‐mean tropical upwelling in the LGM is 11.3–16.9%, 11.2–15.8%, and 4.4–10.2% weaker, respectively, at 100, 70, and 30 hPa. Simulated decreases in annual‐mean mass fluxes at 70 and 100 hPa are caused by a weaker parameterized orographic gravity wave drag and resolved wave drag, respectively. 

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5. Globally resolved surface temperatures since the Last Glacial Maximum

   https://doi.org/10.1038/s41586-021-03984-4  

   Osman, Matthew B.; Tierney, Jessica E.; Zhu, Jiang; Tardif, Robert; Hakim, Gregory J.; King, Jonathan; Poulsen, Christopher J. (November 2021, Nature)