The reduced net carbon uptake over Northern Hemisphere land causes the close-to-normal CO growth rate in 2021 La Niña.

La Niña climate anomalies have historically been associated with substantial reductions in the atmospheric CO growth rate. However, the 2021 La Niña exhibited a unique near-neutral impact on the CO growth rate. In this study, we investigate the underlying mechanisms by using an ensemble of net CO fluxes constrained by CO observations from the Orbiting Carbon Observatory-2 in conjunction with estimates of gross primary production and fire carbon emissions.

Making the case for an International Decade of Radiocarbon.

Radiocarbon (C) is a critical tool for understanding the global carbon cycle. During the Anthropocene, two new processes influenced C in atmospheric, land and ocean carbon reservoirs. First, C-free carbon derived from fossil fuel burning has diluted C, at rates that have accelerated with time.

Soil respiration-driven CO pulses dominate Australia's flux variability.

The Australian continent contributes substantially to the year-to-year variability of the global terrestrial carbon dioxide (CO) sink. However, the scarcity of in situ observations in remote areas prevents the deciphering of processes that force the CO flux variability. In this study, by examining atmospheric CO measurements from satellites in the period 2009-2018, we find recurrent end-of-dry-season CO pulses over the Australian continent.

Regional impacts of COVID-19 on carbon dioxide detected worldwide from space.

Activity reductions in early 2020 due to the coronavirus disease 2019 pandemic led to unprecedented decreases in carbon dioxide (CO) emissions. Despite their record size, the resulting atmospheric signals are smaller than and obscured by climate variability in atmospheric transport and biospheric fluxes, notably that related to the 2019–2020 Indian Ocean Dipole. Monitoring CO anomalies and distinguishing human and climatic causes thus remain a new frontier in Earth system science.

Observations of greenhouse gases as climate indicators.

Humans have significantly altered the energy balance of the Earth's climate system mainly not only by extracting and burning fossil fuels but also by altering the biosphere and using halocarbons. The 3rd US National Climate Assessment pointed to a need for a system of indicators of climate and global change based on long-term data that could be used to support assessments and this led to the development of the National Climate Indicators System (NCIS). Here we identify a representative set of key atmospheric indicators of changes in atmospheric radiative forcing due to greenhouse gases (GHGs), and we evaluate atmospheric composition measurements, including non-CO GHGs for use as climate change indicators in support of the US National Climate Assessment.

Global atmospheric CO inverse models converging on neutral tropical land exchange, but disagreeing on fossil fuel and atmospheric growth rate.

We have compared a suite of recent global CO atmospheric inversion results to independent airborne observations and to each other, to assess their dependence on differences in northern extratropical (NET) vertical transport and to identify some of the drivers of model spread. We evaluate posterior CO concentration profiles against observations from the High-Performance Instrumented Airborne Platform for Environmental Research (HIAPER) Pole-to-Pole Observations (HIPPO) aircraft campaigns over the mid-Pacific in 2009-2011. Although the models differ in inverse approaches, assimilated observations, prior fluxes, and transport models, their broad latitudinal separation of land fluxes has converged significantly since the Atmospheric Carbon Cycle Inversion Intercomparison (TransCom 3) and the REgional Carbon Cycle Assessment and Processes (RECCAP) projects, with model spread reduced by 80% since TransCom 3 and 70% since RECCAP.

Quantifying the Impact of Atmospheric Transport Uncertainty on CO Surface Flux Estimates.

We show that transport differences between two commonly used global chemical transport models, GEOS-Chem and TM5, lead to systematic space-time differences in modeled distributions of carbon dioxide and sulfur hexafluoride. The distribution of differences suggests inconsistencies between the transport simulated by the models, most likely due to the representation of vertical motion. We further demonstrate that these transport differences result in systematic differences in surface CO flux estimated by a collection of global atmospheric inverse models using TM5 and GEOS-Chem and constrained by in situ and satellite observations.

Enhanced North American carbon uptake associated with El Niño.

Long-term atmospheric CO mole fraction and δCO observations over North America document persistent responses to the El Niño-Southern Oscillation. We estimate these responses corresponded to 0.61 (0.

Final-state effects in the radio frequency spectrum of strongly interacting fermions.

We model the impact of final-state interactions on the radio frequency spectrum of a strongly interacting two-component superfluid Fermi gas. In addition to a broad asymmetric peak coming from the breakup of Cooper pairs, we find that, for appropriate parameters, one can observe a sharp symmetric "bound-bound" spectral line coming from the conversion of Cooper pairs in one channel to pairs or molecules in another.

Transforming complex multistability to controlled monostability.

Multistability, a commonly observed feature among nonlinear systems, could be inconvenient under various circumstances. We demonstrate that a control in the form of slow and weak periodic parameter modulation can be effectively applied to transform a complex multistable system to a controlled monostable one. For the representative of a nonlinear system, we choose the Hénon map as the standard model.

Self-similar organization of Gavrilov-Silnikov-Newhouse sinks.

The numerical analyses of the Hénon map suggest the following features. As we increase the value of the control parameter around each stable period of the period-1 branch, an infinitely large series of period n-tupled saddle nodes appears in the following sequence (n= ..