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Trends in global H₂ sources and sinks are analysed from 1990 to 2020, and a comprehensive budget for the decade 2010–2020 is presented.

A re-assessment of the global carbon budget shows the natural land sink is substantially smaller than previously estimated, indicating emerging impacts of climate change on the evolution of the carbon sinks.

Carbon mitigation is considered an important and viable pathway towards climate stabilization, but competition for land is high. Here, Canadell and Schulze consider the sustainable implementation of a number of land-based biological carbon mitigation activities and assess the carbon savings achievable by 2050.

Global warming will intensify wildfires, boosting emissions and increasing the number of premature deaths by about sixfold globally by 2100—shifting the health burden more evenly across regions, demanding stronger international policy responses..

Satellite records combined with global ecosystem models show a persistent and widespread greening over 25–50% of the global vegetated area; less than 4% of the globe is browning. CO₂ fertilization explains 70% of the observed greening trend.

Drought, fires, and human activities have reversed the accumulation of live biomass carbon in the Northern Hemisphere, with total biomass shifting from a positive to a negative trend around 2016.

The terrestrial carbon flux—sources and sinks—under land-use change (LUC) is difficult to quantify. Here, using a LUC dataset drawing on remote sensing and forest inventory data, the authors show that in China the carbon sink from LUC (such as afforestation) may be underestimated.

The degree to which wildfire activity in Australia is affected by climate change is not well quantified. Here, the authors show that the frequency of forest fires and the area burned have increased significantly over recent decades, mainly due to an increase in dangerous fire weather conditions through warmer temperature and circulation changes.

This study reconstructs global fire methane emissions from 2003 to 2020, revealing 27% higher estimates than previous models, which is likely due to undetected small fires and underestimated emission intensity from the coarse-resolution model data.

N₂O emissions from rivers have increased globally by a factor of four between 1900 and 2016, with emissions starting to decline since the early 2000s. Most riverine N₂O emissions come from smaller streams, driven primarily by the use of nitrogen fertilizers in agriculture.

Growth in CO₂ emissions has slowed since the Paris Agreement 5 years ago. The COVID-19 pandemic has caused a drop in emissions of about 7% in 2020 relative to 2019, but strong policy is needed to address underlying drivers and to sustain a decline in global emissions beyond the current crisis.

Between 2005 and 2015, several developed economies experienced decreases in CO₂ emissions. In this study, emissions in 18 countries are broken down and the potential effects of energy and climate policies on emission declines are explored.

This paper presents interrelated indicators for tracking progress towards the Paris Agreement. Findings show broad consistency with keeping warming below 2 °C, but technological advances are needed to achieve net-zero emissions.

Bottom-up and top-down approaches are used to quantify global nitrous oxide sources and sinks resulting from both natural and anthropogenic sources, revealing a 30% increase in global human-induced emissions between 1980 and 2016.

Vegetation change is a key component of the carbon cycle, but quantifying these changes is challenging. Research using passive microwave observations now provides global estimates for forest and non-forest biomass trends over the past two decades.

Existing datasets of nitrogen (N) balance in agriculture are often discrepant. Comparing 13 of them regarding five metrics (fertilizer application, manure application, biological N fixation, atmospheric deposition, and N harvested as crop products) over 1961–2015 reveals why. Recommendations for improving N quantification and an N budget benchmark dataset are also proposed.

Climate science and national emissions reporting communities have historically used different definitions and methods for anthropogenic land-based carbon removals. As the mitigation agenda accelerates, reconciling these differences for comparability and moving towards integration is crucial for enhancing confidence in land-use emission estimates.

COVID-19 pandemic lockdowns have altered global energy demands. Using government confinement policies and activity data, daily CO₂ emissions have decreased by ~17% to early April 2020 against 2019 levels; annual emissions could be down by 7% (4%) if normality returns by year end (mid-June).

Estimating the global cropland N₂O mitigation potential is limited by the uncertainty and variability of direct emission factors (EFs). Here, using a data-driven approach with 1,507 chamber-based field observations of EFs, the study shows that EF variation is primarily driven by climatic and edaphic factors. Two-thirds of the mitigation potential could be achieved on one-fifth of the global harvested area, mainly located in humid subtropical climates and across gleysols and acrisols.

Observed daily changes in CO₂ emissions from across the globe reveal the sectors and countries where pandemic-related emissions declines were most pronounced in 2020.

Northern Hemisphere photosynthesis is thought to respond positively to temperature variations, yet the strength of this relationship may change over time. Here, using a combination of satellite data and models, the authors assess the temporal change of this relationship over the past three decades.

The response of the coupled carbon and water cycles to anthropogenic climate change is unclear. Here, the authors show that terrestrial carbon uptake increased significantly from 1982 to 2011 and that this increase is largely driven by increased water-use efficiency, rather than an increase in water use.

Earth system model simulations of future climate in the Amazon show little agreement. Here, the authors show that biases in internally generated climate explain most of this uncertainty and that the balance between water-saturated and water-limited evapotranspiration controls the Amazon resilience to climate change.

Year-to-year variability in atmospheric CO₂ is strongly influenced by the terrestrial biosphere. Despite increasing anthropogenic emissions, Keenan et al. report a recent pause in the growth rate of atmospheric CO₂using observations and vegetation models, attributed to an enhanced terrestrial carbon sink.

Accelerated storage of terrestrial carbon during the slow warming period (1998–2012) can be predominantly attributed to lower land-use emissions due to decreased tropical forest loss and increased afforestation in the northern temperate regions.

The fertilization effect has the potential to limit the impacts of global warming, but the biosphere is likely to shift into a period in which this effect is saturated.

Consensus on carbon accounting approaches at city-level is lacking and analytic frameworks to systematically link carbon mitigation with the Sustainable Development Goals are limited. A new accounting approach anchored upon key physical provisioning systems can help to address these knowledge gaps and facilitate urban transitions.

Efforts to control climate change require the stabilization of atmospheric carbon dioxide concentrations. An assessment of the trends in sources and sinks of atmospheric carbon dioxide suggests that the sinks are not keeping up with the increase in carbon dioxide emissions, but uncertainties are still large.

The Paris Agreement has increased the incentive to verify reported anthropogenic carbon dioxide emissions with independent Earth system observations. Reliable verification requires a step change in our understanding of carbon cycle variability.

The latest carbon dioxide emissions continue to track the high end of emission scenarios, making it even less likely global warming will stay below 2 °C. A shift to a 2 °C pathway requires immediate significant and sustained global mitigation, with a probable reliance on net negative emissions in the longer term.

Bioenergy with carbon capture and storage could be used to remove carbon dioxide from the atmosphere. However, its credibility as a climate change mitigation option is unproven and its widespread deployment in climate stabilization scenarios might become a dangerous distraction.

Rapid growth in global CO₂ emissions from fossil fuels and industry ceased in the past two years, despite continued economic growth. Decreased coal use in China was largely responsible, coupled with slower global growth in petroleum and faster growth in renewables.

Cities are becoming increasingly important in combatting climate change, but their overall role in global solution pathways remains unclear. Here we suggest structuring urban climate solutions along the use of existing and newly built infrastructures, providing estimates of the mitigation potential.

The net balance of terrestrial biogenic greenhouse gases produced as a result of human activities and the climatic impact of this balance are uncertain; here the net cumulative impact of the three greenhouse gases, methane, nitrous oxide and carbon dioxide, on the planetary energy budget from 2001 to 2010 is a warming of the planet.

Uncertainties and subjective choices affecting remaining carbon budgets should be fully considered when applying them to international and national climate policies.

Methane is an important greenhouse gas, responsible for about 20% of the warming induced by long-lived greenhouse gases since pre-industrial times. A compilation of observations and results from chemical transport, ecosystem and climate chemistry models suggests that a rise in wetland and fossil fuel emissions probably accounts for the renewed increase in global methane levels after 2006.

The unusually large land carbon sink reported in 2011 can mostly be attributed to semi-arid vegetation growth in the Southern Hemisphere following increased rainfall and long-term greening trends.

Freshwater aquaculture may contribute as much as half of all freshwater greenhouse gas emissions in China and could scale as the industry grows, according to a synthesis of methane and nitrous oxide emission observations across China from 1980-2022.

Underlying net-zero GHG accounting approaches is the assumption that emissions can be balanced by removals such that their net climate effect is zero. However, CO₂ removals may not be equal and opposite to CO₂ emissions in their climate impact, indicating the need to consider non-CO₂ effects.

The terrestrial biosphere stores carbon in a land carbon sink, offsetting emissions of carbon into the atmosphere. This Review demonstrates that the magnitude of the land carbon sink has increased over time, but that its stability in the future is less clear and depends on climate impacts and effective implementation of nature-based solutions.

Scenario analyses suggest that negative emissions technologies (NETs) are necessary to limit dangerous warming. Here the authors assess the biophysical limits to, and economic costs of, the widespread application of NETs.

Future cumulative CO₂ emissions consistent with a given warming limit are a finite common global resource that countries need to share — a carbon quota. Strategies to share a quota consistent with a 2 °C warming limit range from keeping the present distribution to reaching an equal per-capita distribution of cumulative emissions. This Perspective shows that a blend of these endpoints is the most viable solution.

Research addressing sustainability issues is more effective if ‘co-produced’ by academics and non-academics, but definitions of co-production vary. This Perspective presents four knowledge co-production principles for sustainability research and guides on how to engage in co-productive practices.