Leonard F. Borchert

Leonard F. Borchert
University of Hamburg | UHH · Zentrum für Erdsystemforschung und Nachhaltigkeit

Dr. rer. nat.
Passionate about climate extremes & near-term climate predictions. How can our research have a larger impact on society?

About

33
Publications
3,552
Reads
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189
Citations
Additional affiliations
April 2021 - April 2022
Ecole Normale Supérieure de Paris
Position
  • PostDoc Position
September 2019 - March 2021
Sorbonne Université
Position
  • PostDoc Position
July 2018 - July 2019
Max Planck Institute for Meteorology
Position
  • PostDoc Position
Education
October 2012 - March 2015
University of Hamburg
Field of study
  • Integrated Climate System Sciences
October 2009 - September 2012
Universität Bremen
Field of study
  • Geosciences

Publications

Publications (33)
Article
Full-text available
Quantifying signals and uncertainties in climate models is essential for the detection, attribution, prediction and projection of climate change1–3. Although inter-model agreement is high for large-scale temperature signals, dynamical changes in atmospheric circulation are very uncertain4. This leads to low confidence in regional projections, espec...
Article
Full-text available
Due to its wide‐ranging impacts, predicting decadal variations of sea surface temperature (SST) in the subpolar North Atlantic remains a key goal of climate science. Here, we compare the representation of observed subpolar SST variations since 1960 in initialized and uninitialized historical simulations from the 5th and 6th phases of the Coupled Mo...
Article
Full-text available
CMIP5 models have been shown to exhibit rapid cooling events in their projections of the North Atlantic subpolar gyre. Here, we analyze the CMIP6 archive, searching for such rapid cooling events in the new generation of models. Four models out of 35 exhibit such instabilities. The climatic impacts of these events are large on decadal timescales, wi...
Article
Full-text available
Decadal Climate Predictions (DCP) have gained considerable attention for their potential utility in promoting optimised plans of adaptation to climate change and variability. Their effective applicability to a targeted problem is nevertheless conditional on a detailed evaluation of their ability to simulate the near-term climate evolution under spe...
Article
Full-text available
We assess the capability of decadal prediction simulations from the Coupled Model Intercomparison Project phase 6 (CMIP6) archive to predict European summer temperature during the period 1970-2014. Using a multi-model ensemble average, we show that Southern European (SEU) summer temperatures are highly predictable for up to ten years in CMIP6. Much...
Article
Full-text available
We combine a machine learning method and ensemble climate predictions to investigate windows of opportunity for seasonal predictability of European summer climate associated with the North Atlantic jet stream. We particularly focus on the impact of North Atlantic spring sea surface temperatures (SST) on the four dominant atmospheric teleconnections...
Article
Full-text available
We investigate the impact of the strength of the Atlantic Meridional Overturning Circulation (AMOC) at 26 • N on the prediction of North Atlantic sea surface temperature anomalies (SSTAs) a season ahead. We test the dependence of sea surface temperate (SST) predictive skill in initialised hindcasts on the phase of the AMOC at 26 • N, invoking a see...
Preprint
Full-text available
We assess the capability of decadal prediction simulations from the Coupled Model Intercomparison Project phase 6 (CMIP6) archive to predict European summer temperature during the period 1970-2014. Using a multi-model ensemble average from 8 decadal prediction systems, we show that European summer temperatures are highly predictable for up to 10 ye...
Preprint
Full-text available
Decadal Climate Predictions (DCP) have gained considerable attention for their potential utility in promoting optimised plans of adaptation to climate change and variability. Their effective applicability to a targeted problem is nevertheless conditional on a detailed evaluation of their ability to simulate the near-term climate evolution under spe...
Article
Full-text available
Observations can facilitate evaluation and provide constraints that are relevant to future predictions and projections. Constraints for uninitialized projections are generally based on model performance in simulating climatology and climate change. For initialized predictions, skill scores over the hindcast period provide insight into the relative...
Presentation
Full-text available
We use a neural network-based classifier, i.e. self-organising maps to evaluate the Max Planck Institute Earth System Model seasonal prediction system. We focus on the model performance in representing the dominant atmospheric teleconnections linked to the North Atlantic Jet Stream, and their impact on European summer climate predictability. We fur...
Preprint
Full-text available
We investigate the impact of the strength of the Atlantic Meridional Overturning Circulation (AMOC) at 26° N on the prediction of North Atlantic sea surface temperature anomalies (SSTA) a season ahead. We consider the physical mechanism proposed by Duchez et al. (2016a) and test the dependence of SST predictive skill in initialised hindcasts on the...
Article
Full-text available
Plain Language Summary The Atlantic multidecadal variability is an observed fluctuation of North Atlantic ocean surface temperatures on multidecadal time scales. It strongly influences climatic conditions over the surrounding continents in the North Atlantic region as well as in remote areas. Therefore, it is essential to understand the underlying...
Presentation
Full-text available
Does a decadal prediction system (DCP) significantly performs better in some specific contexts rather than in others? If yes, in which ones? • Does the statistical de-biasing implies skill improvement? • How these information can be used to support climate services ? Overview We comprehensively analysed the potentiality of the IPSL DCP system in pr...
Article
Full-text available
The north Atlantic subpolar gyre (SPG) has been widely implicated as the source of large-scale changes in the subpolar marine environment. However, inconsistencies between indices of SPG-strength have raised questions about the active role SPG-strength and size play in determining water properties in the eastern subpolar North Atlantic (ENA). Here,...
Article
Full-text available
We identify sub‐decadal variations in European summer temperatures in coupled and uncoupled century‐long reanalyses. Spectral analyses reveal significant peaks at 5‐10 years in the mid‐20th Century. The sub‐decadal variations show substantial amplitudes of ~1‐1.5°C, associated with extremely warm summers during their positive phases. We use forced...
Article
Full-text available
We use a decadal prediction system with the Coupled Model Intercomparison Project Phase 6 (CMIP6) version of the coupled Max Planck Institute Earth System Model (MPI-ESM-HR) to predict the probability of occurrence for extremely warm summers in the Northern Hemisphere. An assimilation run with MPI-ESM-HR shows a robust response of summer temperatur...
Article
Full-text available
We demonstrate in this paper that conventional time-averaged decadal hindcast skill estimates can overestimate or underestimate the credibility of an individual decadal climate forecast. We show that hindcast skill in a long period can be higher or lower than skill in its subperiods. Instead of using time-averaged hindcast skill measures, we propos...
Article
Full-text available
An analysis of a three-member-ensemble of initialized coupled simulations with the MPI-ESM-LR covering the period 1901-2010 shows that Atlantic northward ocean heat transport (OHT) at 50°N influences surface temperature variability in the North Atlantic region for several years. 3-10 years after strong OHT phases at 50°N, a characteristic pattern o...
Thesis
Full-text available
The possibility of credible climate forecasts for several years ahead - on the decadal time scale - has received considerable public and economic attention. Scientific studies quantify the credibility of such forecasts by evaluating the average predictive quality (skill) over the last 50-60 years (in so-called hindcasts). Decadal hindcasts of surfa...
Poster
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We use an initialized version of the MPI-ESM-LR GCM to demonstrate the influence of northward heat transport in the Atlantic Ocean on the interannual predictability of surface temperatures in the North Atlantic.
Poster
Full-text available
Recent studies found an impact of the Atlantic Meridional Overturning Circulation (AMOC) through sea surface temperatures (SSTs) and ocean-atmosphere surface heat fluxes (SHFs) on North Atlantic (NA) climate on interannual time scales. As fluctuations in SSTs and SHFs as well as AMOC and oceanic heat transport (OHT) are highly model dependent and c...
Poster
Full-text available
Recent studies found an impact of the Atlantic Meridional Overturning Circulation (AMOC) through sea surface temperatures (SSTs) and ocean-atmosphere surface heat fluxes (SHFs) on North Atlantic (NA) climate on interannual time scales. Since fluctuations in SSTs and SHFs as well as AMOC and oceanic heat transport (OHT) are highly model dependent an...
Article
Full-text available
Ecosystem services play an increasingly important role in modern coastal and marine research as they are a fundamental concept that can be used to couple natural and social sciences aspects of Environmental Sciences. Assigning a value to a functioning ecosystem is the logical connection between the given environmental conditions and the well-being...
Poster
Full-text available
Climate Change might impose large changes to the environment by the end of the century, with global mean temperatures possibly rising to more than 2°C above the pre-industrial state. Mitigation of Climate Change in the form of reducing anthro- pogenic greenhouse gas emissions is widely considered to be the appropriate reaction to this development....

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Projects

Project (1)
Project
Can decadal predictions of North Atlantic climate be refined (or constrained) using the mean performance of the prediction model? We aim to understand physical processes that dominate decadal predictions of North Atlantic and European climate, with a particular focus on time-dependence of prediction skill. The role of variations of the North Atlantic subpolar gyre is hypothesized to be of particular interest for such predictions. The analysis is carried out in the CMIP6 historical and DCPP ensembles.