Using the atmospheric CO growth rate to constrain the CO flux from land use and land cover change since 1900.

We explore the ability of the atmospheric CO record since 1900 to constrain the source of CO from land use and land cover change (hereafter "land use"), taking account of uncertainties in other terms in the global carbon budget. We find that the atmospheric constraint favors land use CO flux estimates with lower decadal variability and can identify potentially erroneous features, such as emission peaks around 1960 and after 2000, in some published estimates. Furthermore, we resolve an offset in the global carbon budget that is most plausibly attributed to the land use flux.

Impact of Changing Winds on the Mauna Loa CO Seasonal Cycle in Relation to the Pacific Decadal Oscillation.

Long-term measurements at the Mauna Loa Observatory (MLO) show that the CO seasonal cycle amplitude (SCA) increased from 1959 to 2019 at an overall rate of 0.22   0.034 ppm decade while also varying on interannual to decadal time scales.

A multi-city urban atmospheric greenhouse gas measurement data synthesis.

Urban regions emit a large fraction of anthropogenic emissions of greenhouse gases (GHG) such as carbon dioxide (CO) and methane (CH) that contribute to modern-day climate change. As such, a growing number of urban policymakers and stakeholders are adopting emission reduction targets and implementing policies to reach those targets. Over the past two decades research teams have established urban GHG monitoring networks to determine how much, where, and why a particular city emits GHGs, and to track changes in emissions over time.

On the Detection of COVID-Driven Changes in Atmospheric Carbon Dioxide.

We assess the detectability of COVID-like emissions reductions in global atmospheric CO concentrations using a suite of large ensembles conducted with an Earth system model. We find a unique fingerprint of COVID in the simulated growth rate of CO sampled at the locations of surface measurement sites. Negative anomalies in growth rates persist from January 2020 through December 2021, reaching a maximum in February 2021.

Strong Southern Ocean carbon uptake evident in airborne observations.

The Southern Ocean plays an important role in determining atmospheric carbon dioxide (CO), yet estimates of air-sea CO flux for the region diverge widely. In this study, we constrained Southern Ocean air-sea CO exchange by relating fluxes to horizontal and vertical CO gradients in atmospheric transport models and applying atmospheric observations of these gradients to estimate fluxes. Aircraft-based measurements of the vertical atmospheric CO gradient provide robust flux constraints.

Unusual characteristics of the carbon cycle during the 2015-2016 El Niño.

The 2015-2016 El Niño was one of the strongest on record, but its influence on the carbon balance is less clear. Using Northern Hemisphere atmospheric CO observations, we found both detrended atmospheric CO growth rate (CGR) and CO seasonal-cycle amplitude (SCA) of 2015-2016 were much higher than that of other El Niño events. The simultaneous high CGR and SCA were unusual, because our analysis of long-term CO observations at Mauna Loa revealed a significantly negative correlation between CGR and SCA.

Impacts of Changes in Atmospheric O on Human Physiology. Is There a Basis for Concern?

Concern is often voiced over the ongoing loss of atmospheric O. This loss, which is caused by fossil-fuel burning but also influenced by other processes, is likely to continue at least for the next few centuries. We argue that this loss is quite well understood, and the eventual decrease is bounded by the fossil-fuel resource base.

Changes to Carbon Isotopes in Atmospheric CO Over the Industrial Era and Into the Future.

In this "Grand Challenges" paper, we review how the carbon isotopic composition of atmospheric CO has changed since the Industrial Revolution due to human activities and their influence on the natural carbon cycle, and we provide new estimates of possible future changes for a range of scenarios. Emissions of CO from fossil fuel combustion and land use change reduce the ratio of C/C in atmospheric CO (δCO). This is because C is preferentially assimilated during photosynthesis and δC in plant-derived carbon in terrestrial ecosystems and fossil fuels is lower than atmospheric δCO.

Extensive land cover change across Arctic-Boreal Northwestern North America from disturbance and climate forcing.

A multitude of disturbance agents, such as wildfires, land use, and climate-driven expansion of woody shrubs, is transforming the distribution of plant functional types across Arctic-Boreal ecosystems, which has significant implications for interactions and feedbacks between terrestrial ecosystems and climate in the northern high-latitude. However, because the spatial resolution of existing land cover datasets is too coarse, large-scale land cover changes in the Arctic-Boreal region (ABR) have been poorly characterized. Here, we use 31 years (1984-2014) of moderate spatial resolution (30 m) satellite imagery over a region spanning 4.

A Multiplatform Inversion Estimation of Statewide and Regional Methane Emissions in California during 2014-2016.

California methane (CH) emissions are quantified for three years from two tower networks and one aircraft campaign. We used backward trajectory simulations and a mesoscale Bayesian inverse model, initialized by three inventories, to achieve the emission quantification. Results show total statewide CH emissions of 2.

A successful prediction of the record CO rise associated with the 2015/2016 El Niño.

In early 2016, we predicted that the annual rise in carbon dioxide concentration at Mauna Loa would be the largest on record. Our forecast used a statistical relationship between observed and forecast sea surface temperatures in the Niño 3.4 region and the annual CO rise.

Atmospheric evidence for a global secular increase in carbon isotopic discrimination of land photosynthesis.

A decrease in the C/C ratio of atmospheric CO has been documented by direct observations since 1978 and from ice core measurements since the industrial revolution. This decrease, known as the C-Suess effect, is driven primarily by the input of fossil fuel-derived CO but is also sensitive to land and ocean carbon cycling and uptake. Using updated records, we show that no plausible combination of sources and sinks of CO from fossil fuel, land, and oceans can explain the observed C-Suess effect unless an increase has occurred in the C/C isotopic discrimination of land photosynthesis.

Overestimate of committed warming.

Palaeoclimate variations are an essential component in constraining future projections of climate change as a function of increasing anthropogenic greenhouse gases. The Earth System Sensitivity (ESS) describes the multi-millennial response of Earth (in terms of global mean temperature) to a doubling of CO concentrations. A recent study used a correlation of inferred temperatures and radiative forcing from greenhouse gases over the past 800,000 years to estimate the ESS from present day CO is about 9°C, and to imply a long-term commitment of 3–7°C even if greenhouse gas levels remain at present-day concentrations.

Carbon dioxide and methane measurements from the Los Angeles Megacity Carbon Project - Part 1: calibration, urban enhancements, and uncertainty estimates.

We report continuous surface observations of carbon dioxide (CO) and methane (CH) from the Los Angeles (LA) Megacity Carbon Project during 2015. We devised a calibration strategy, methods for selection of background air masses, calculation of urban enhancements, and a detailed algorithm for estimating uncertainties in urban-scale CO and CH measurements. These methods are essential for understanding carbon fluxes from the LA megacity and other complex urban environments globally.

Enhanced seasonal CO2 exchange caused by amplified plant productivity in northern ecosystems.

Atmospheric monitoring of high northern latitudes (above 40°N) has shown an enhanced seasonal cycle of carbon dioxide (CO2) since the 1960s, but the underlying mechanisms are not yet fully understood. The much stronger increase in high latitudes relative to low ones suggests that northern ecosystems are experiencing large changes in vegetation and carbon cycle dynamics. We found that the latitudinal gradient of the increasing CO2 amplitude is mainly driven by positive trends in photosynthetic carbon uptake caused by recent climate change and mediated by changing vegetation cover in northern ecosystems.

Interannual variability in the oxygen isotopes of atmospheric CO2 driven by El Niño.

The stable isotope ratios of atmospheric CO(2) ((18)O/(16)O and (13)C/(12)C) have been monitored since 1977 to improve our understanding of the global carbon cycle, because biosphere-atmosphere exchange fluxes affect the different atomic masses in a measurable way. Interpreting the (18)O/(16)O variability has proved difficult, however, because oxygen isotopes in CO(2) are influenced by both the carbon cycle and the water cycle. Previous attention focused on the decreasing (18)O/(16)O ratio in the 1990s, observed by the global Cooperative Air Sampling Network of the US National Oceanic and Atmospheric Administration Earth System Research Laboratory.

The atmospheric signature of carbon capture and storage.

Compared with other industrial processes, carbon capture and storage (CCS) will have an unusual impact on atmospheric composition by reducing the CO(2) released from fossil-fuel combustion plants, but not reducing the associated O(2) loss. CO(2) that leaks into the air from below-ground CCS sites will also be unusual in lacking the O(2) deficit normally associated with typical land CO(2) sources, such as from combustion or ecosystem exchanges. CCS may also produce distinct isotopic changes in atmospheric CO(2).

Greenhouse gases in the Earth system: setting the agenda to 2030.

What do we need to know about greenhouse gases? Over the next 20 years, how should scientists study the role of greenhouse gases in the Earth system and the changes that are taking place? These questions were addressed at a Royal Society scientific Discussion Meeting in London on 22-23 February 2010, with over 300 participants.

Ocean deoxygenation in a warming world.

Ocean warming and increased stratification of the upper ocean caused by global climate change will likely lead to declines in dissolved O2 in the ocean interior (ocean deoxygenation) with implications for ocean productivity, nutrient cycling, carbon cycling, and marine habitat. Ocean models predict declines of 1 to 7% in the global ocean O2 inventory over the next century, with declines continuing for a thousand years or more into the future. An important consequence may be an expansion in the area and volume of so-called oxygen minimum zones, where O2 levels are too low to support many macrofauna and profound changes in biogeochemical cycling occur.