Glaciers in California’s Sierra Nevada are likely disappearing for the first time in the Holocene

The projected loss of glaciers in California’s Sierra Nevada is likely unprecedented in at least the past 30,000 years.

Colegio de Geólogos (@cgeologos)

Con ocasión de la inclusión de la palabra "Antropoceno" como época geológica en el diccionario, Juan Carlos Gutiérrez-Marco investigador de Instituto de Geociencias (CSIC-UCM), (+)

Reconstructing Holocene temperatures in time and space using paleoclimate data assimilation

<p><strong class="journal-contentHeaderColor">Abstract.</strong> Paleoclimatic records provide valuable information about Holocene climate, revealing aspects of climate variability for a multitude of sites around the world. However, such data also possess limitations. Proxy networks are spatially uneven, seasonally biased, uncertain in time, and present a variety of challenges when used in concert to illustrate the complex variations of past climate. Paleoclimatic data assimilation provides one approach to reconstructing past climate that can account for the diverse nature of proxy records while maintaining the physics-based covariance structures simulated by climate models. Here, we use paleoclimate data assimilation to create a spatially complete reconstruction of temperature over the past 12 000 years using proxy data from the Temperature 12k database and output from transient climate model simulations. Following the last glacial period, the reconstruction shows Holocene temperatures warming to a peak near 6400 years ago followed by a slow cooling toward the present day, supporting a mid-Holocene which is at least as warm as the preindustrial. Sensitivity tests show that if proxies have an overlooked summer bias, some apparent mid-Holocene warmth could actually represent summer trends rather than annual mean trends. Regardless, the potential effects of proxy seasonal biases are insufficient to align the reconstructed global mean temperature with the warming trends seen in transient model simulations.</p>

H2Q on Twitter

“Un hilo sobre el #Holoceno para comprender los ciclos de la tierra: #Mesolítico: Hace 12.000 años la temperatura media era 18ºC más baja que hoy, tras 70.000 años bajo la Glaciación de Würm. Gran Bretaña se unía con Europa y los glaciares cubrían en hemisferio Norte.”

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