We developed a computer model that simulates forests plantations at global scale and how fast such forests can take up CO2 from the atmosphere. Using this new model, we performed simulations for a scenario in which a large fraction (14 %) of global croplands and pastures are either converted to planted forests or natural forests. We find that planted forests take up CO2 substantially faster than natural forests and are therefore a viable strategy for reducing climate change.
Earth's climate can be studied as a system with different components that can be strongly altered by human influence. One possibility is that the El Niño phenomenon becomes more frequent. We investigated the potential impacts of the most frequent El Niño: a permanent one. The most noticeable impacts include variations in global water availability and vegetation productivity, potential dieback of the Amazon rainforest, greening of western North America, and further aridification of Australia.
This study contributes to a better understanding of how large-scale dust transport can be organized from northwest Africa to the US, Amazon basin, and Europe and might be due in part to Kelvin waves. We also think there is still a need to study major historical dust events that occurred in this region to confirm that this location is suitable and responsible for the generation of the Kelvin waves and the transport of dust on a regular basis.
Natural systems evolve towards a state of maximum power, including estuarine circulation. The energy of lighter fresh water drives circulation, while it dissipates by friction. This rotational flow causes the spread of salinity, which is represented by the dispersion coefficient. In this paper, the maximum power concept provides a new equation for this coefficient. Together with the steady-state equation, this results in a new analytical model for density-driven salinity intrusion.
Various minor carbon flows such as trace gas emissions, disturbance-induced emissions, and subsurface exports can affect the carbon budget of terrestrial ecosystems in complicated ways. This study assessed how much these minor flows influence the carbon budget using a process-based model. It was found that the minor flows, though small in magnitude, could significantly affect net carbon budget at as much strengths as major flows, implying their long-term importance in Earth's climate system.
This modeling study is the first one to look at the suitability and collateral effects of direct CO2 injection into the deep ocean as a means to bridge the gap between CO2 emissions and climate impacts of an intermediate CO2 emission scenario and a temperature target on a millennium timescale, such as the 1.5 °C climate target of the Paris Agreement.
Simple climate models (SCMs) underlie many important scientific and decision-making endeavors. This illustrates the need for their use to be rooted in a clear understanding of their fundamental responses. In this study, we provide a comprehensive assessment of model performance by evaluating the fundamental responses of several SCMs. We find biases in some responses, which have implications for decision science. We conclude by recommending a standard set of validation tests for any SCM.
We compute the global mean temperature increase at which the costs from climate-change damages and climate-change mitigation are minimal. This temperature is computed robustly around 2 degrees of global warming across a wide range of normative assumptions on the valuation of future welfare and inequality aversion.
Using a sub-daily dataset of in situ observations, we have performed a study to see how the distributions of temperatures and wind speeds have changed over the last 45 years. Changes in the location or shape of these distributions show how extreme temperatures or wind speeds have changed. Our results show that cool extremes are warming more rapidly than warm ones in high latitudes but that in other parts of the world the opposite is true.
Weather and climate predictions potentially improve by dynamically combining different models into a supermodel. A crucial step is to train the supermodel on the basis of observations. Here, we apply two different training methods to the global atmosphere–ocean–land model SPEEDO. We demonstrate that both training methods yield climate and weather predictions of superior quality compared to the individual models. Supermodel predictions can also outperform the commonly used multi-model mean.
Concerns are growing that human activity will lead to social and environmental breakdown, but it is hard to anticipate when and where such breakdowns might occur. We developed a new model of land management decisions in Europe to explore possible future changes and found that decision-making that takes into account social and environmental conditions can produce unexpected outcomes that include societal breakdown in challenging conditions.
Our study reveals that the latitudinal position and intensity of Southern Hemisphere trades and westerlies are correlated. In the last decades the westerlies have shifted poleward and intensified. Furthermore, the latitudinal shifts and intensity of the trades and westerlies impact the sea surface temperatures around southern Africa and in the South Benguela upwelling region. The future development of wind stress depends on the strength of greenhouse gas forcing.
Sabrina Hempel, Christoph Menz, Severino Pinto, Elena Galán, David Janke, Fernando Estellés, Theresa Müschner-Siemens, Xiaoshuai Wang, Julia Heinicke, Guoqiang Zhang, Barbara Amon, Agustín del Prado, and Thomas Amon
Decreasing humidity and increasing wind speed regionally alleviate the heat load on farm animals, but future temperature rise considerably increases the heat stress risk. Livestock housed in open barns (or on pastures), such as dairy cattle, is particularly vulnerable. Without adaptation, heat waves will considerably reduce the gross margin of a livestock producer. Negative effects on productivity, health and animal welfare as well as increasing methane and ammonia emissions are expected.
We find that sulfate aerosols are more effective in cooling the climate system when they reside higher in the stratosphere. We explain this sensitivity in terms of radiative forcing at the top of the atmosphere. Sulfate aerosols heat the stratospheric layers, causing an increase in stratospheric water vapor content and a reduction in high clouds. These changes are larger when aerosols are prescribed near the tropopause, offsetting part of the aerosol-induced negative radiative forcing/cooling.
Decadal climate predictions are valuable to society as they allow us to estimate climate conditions several years in advance. We analyze the latest version of the German MiKlip prediction system (https://www.fona-miklip.de) and assess the effect of the model resolution on the skill of the system. The increase in the resolution of the system reduces the bias and significantly improves the forecast skill for North Atlantic extratropical winter dynamics for lead times of two to five winters.