The past 12,000 years reveal a more complex climate history than previously thought – any better with that?

Newly published Open Access Paper.

This is a summary and an introduction. The article has no fee wall.

The complex space-time structure of the Holocene Thermal Maximum

Nature Communications episode 13Number of articles: 5662 (2022) Quote this post

Data

abstract

Inconsistencies between Holocene climate reconstructions and numerical model simulations question the robustness of proxy climate models and temperature profiles. Climatic reconstructions show a mid-early Holocene maximum (HTM), followed by gradual cooling, while climate models show continued warming. This difference implies a seasonal bias in proxy-based climate reconstructions or that the sensitivity of the climate model to stations and responses needs to be re-evaluated. Here, we analyze a global database of ancient Holocene temperature records to investigate the spatial structure of the HTM. Continental proxy records in the middle and high latitudes of the Northern Hemisphere describe a “classical” HTM (8–4 ka). In contrast, marine proxy records from the same latitude show an earlier HTM (11–7ka), while obvious temperature anomalies are missing in the tropics. The results indicate a heterogeneous response to climate pressures and highlight the lack of uniformity of the HTM globally.

Introduce

Natural climate variability is the result of many climates and responds with heterogeneous spatial representations. Greenhouse gases, volcanic radiation, and solar radiation apply fairly uniformly across the Earth’s surface, while insulation varies with both latitude and season. In addition, climate system responses can be amplified or attenuated by responses inherent to changes in geography, albedo, and by variations in ocean and/or atmospheric circulation. The atmosphere (re)distributes heat across the Earth’s surface. Our understanding of climate processes is limited by the relatively short timescales and heterogeneous spatial extent of the instrumental records. Evidence of past climate change is gathered through the testimony of geological archives, thus providing a unique opportunity to contextualize ongoing changes and assess the effects of climate change. performance of the climate model over time periods beyond the decadent climate variability recorded during the instrument period.

The temperature on the Earth’s surface directly responds to the global radiative force and thus provides fundamental insights into the state of the climate system. Over the past decades, quantitative indicators of past temperatures (hereinafter referred to as “proxies”) based on different types of archives have been used to reconstruct climate change. in a variety of time scales. Improvements in both the spatial coverage and temporal resolution of temperature proxy records have led to the development of regional and global temperature reconstructions, allowing the scientific community to highlights the unprecedented nature of anthropogenic climate change throughout the common era.^first,2 and Holocene^3,4,5,6. The global temperature reconstruction consistently describes the Holocene maximum (HTM) which is typically between 10 and 5 ka.^4,5 with the maximum probability centered around 6.45 ka⁴. The HTM was followed by global cooling until the end of the 19th century CE, interrupted by the rapid and sustained warming that characterizes the present-forward industrial era. However, cooling trends inferred from proxy records, which are often attributed to attenuation of high northern latitudes, cannot be resolved in numerical simulations.⁷. Indeed, in climate models, the simulated global average temperature is mainly driven by the extent of ice and the concentration of greenhouse gases in the atmosphere, which collectively imposes continuous warming over the course of the year. Holocene process⁷.

This difference between proxy data and model simulations is often referred to as the “Holocene Temperature Conundrum.”⁷, casts doubt on the underlying conceptual framework explaining temperature proxies and on climate modeling skills. For example, it has been suggested that temperature reconstructions may be seasonally biased^7,8 and/or skewed global mean due to overrepresentation of North Atlantic sea surface temperature (SST) records^5,6,7. However, model-data inconsistencies can also be the result of geographically different trends due to sea ice dynamics.⁹pole amplification^tenmodel resolution is not enough¹¹and the boundary conditions used in the numerical simulation^twelfth. Although HTM has been thoroughly studied from a global perspective^3,4,5,6,7Its spatial-temporal characteristics have received relatively little attention, although local and regional trends differ markedly from the average global reproducibility trends.^3,13.

In this study, we seek to document the spatial-technological expression of the HTM in marine and continental territories to elucidate the fortresses and responses underlying Holocene climate evolution.⁹.

Here is the press release from EurekAlert!

An international team of researchers from Germany, the United Kingdom, Switzerland, Canada and France has revealed the complexity of temperature trends over the past 12,000 years.

A peer-reviewed publication

MARUM – SEA ENVIRONMENTAL SCIENCE CENTER, UNIVERSITY OF TECHNOLOGY

In this new study, scientists used the largest available database of past temperature reconstructions spanning 12,000 years to thoroughly investigate the geographic pattern of temperature change. during the Holocene. Olivier Cartapanis and colleagues found that, contrary to previously thought, there was no globally synchronized warm period during the Holocene. Instead, the warmest temperatures were found at different times not only in different regions but also between oceans and over land. This raises the question of how meaningful it really is to compare global average temperatures between reconstructions and models.

According to lead author Olivier Cartapanis, “the results challenge the model of the Holocene Thermal Maximum occurring around the world at the same time”. And, while the warmest temperatures were reached between 4,000 and 8,000 years ago in Western Europe and North America, ocean surface temperatures have cooled from about 10,000 years ago at mid-latitudes and remained stable in the region. Tropic. Regional variation in the duration of maximum temperatures suggests that isolation at high latitudes and ice extents played a key role in driving climate change throughout the Holocene.

“Because ecosystems and people don’t experience Earth’s average temperature,” said Lukas Jonkers, study co-author and researcher at MARUM – Center for Marine Environmental Science in Bremen, Germany. , but affected by regional and local changes in climate, models need to capture the correct spatial and temporal patterns of climate change to guide policymakers”. Thus, the new work of Cartapanis and colleagues offers a clear target for climate models as the ability of the climate model to reproduce Holocene climate variations over space and time, will increase confidence in their regional projections of future climate change.

MARUM create basic scientific knowledge about the role of the oceans and ocean floors in the Earth system as a whole. The dynamics of the oceans and ocean floors significantly impact the entire Earth system through the interaction of geological, physical, biological and chemical processes. These affect both climate and the global carbon cycle, while creating unique biological systems. MARUM is committed to conducting basic and unbiased research for the benefit of society and the marine environment, and in line with the United Nations Sustainable Development Goals. It publishes quality-assured and publicly available scientific data. MARUM informs the public about new discoveries in the marine environment and provides practical knowledge through dialogue with society. MARUM cooperates with commercial and industrial partners in line with the goal of protecting the marine environment.

JOURNEYS

Nature Communications

DOI

10.1038 / s41467-022-33362-1

ARTICLE TITLE

The complex space-time structure of the Holocene Thermal Maximum

ARTICLE PUBLICATION DATE

October 3, 2022

From EurekAlert!