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Recent warming and freshening of the Southern Ocean can be attributed to human-induced greenhouse gas emissions, with stratospheric ozone depletion also playing a role, according to a synthesis of observations and climate model simulations.

Quantifying the temperature impacts of anthropogenic emissions helps monitor proximity to the Paris Agreement goals. Human activities warmed global mean temperature during the past decade by 0.9 to 1.3 °C above 1850–1900 values, with 1.2 to 1.9 °C from greenhouse gases and −0.7 to −0.1 °C from aerosols.

Following a hypothesized complete cessation of carbon dioxide emissions, global climate models simulate approximately constant global mean temperatures for centuries. Long-term simulations with the Canadian Earth System Model suggest that, on these timescales, regional changes in temperature and precipitation are nevertheless significant, and that Southern Ocean warming at intermediate depths could affect the stability of Antarctic ice.

A new dataset of surface specific humidity observations is used, along with output from a coupled climate model, to identify a significant increase in global mean surface specific humidity over the late twentieth century that is mainly attributable to human influence, indicating that human-induced climate change has already had a significant influence on this important climate variable.

This paper shows that the ratio of global warming to cumulative CO₂ emissions is constant due to complex interactions of physical and biogeochemical processes, and not because heat and carbon are mixed into the ocean by similar processes.

Polar temperatures have been warming significantly over the past few decades. A comparison between observational temperature records and model simulations shows that temperature changes in both the Arctic and Antarctic regions can be attributed to human activity.

This study investigates the relative contributions to Arctic warming from natural and anthropogenic forcers—greenhouse gases and aerosols. About 60% of greenhouse-gas warming is found to be offset by other anthropogenic forcings, which is greater than observed on a global scale.

A dominant influence of anthropogenic greenhouse gas increases on Arctic sea ice area is detectable in all months. By scaling climate models’ sea ice response to best match observed trends, an ice-free Arctic in September is projected under all scenarios.

Climate sensitivity models may inaccurately characterize the full Earth system response, as they ignore changes in the carbon cycle, aerosols, land use and land cover. A combination of a simplified climate model, a range of simulations from a recent model intercomparison and historical constraints now show that, independent of the timing of emissions or the atmospheric concentration of CO₂, emitting a trillion tonnes of carbon will cause global warming of 1.0 to 2.1 degrees Celsius.

Internal variability can strongly influence global temperature trends. Here the authors show that if the internal variability in the eastern tropical Pacific is removed from recent trends, the constrained projected warming with future CO₂ emissions is higher than currently expected.

A study that compares observed changes in precipitation over land averaged across latitudinal bands with changes simulated by climate models finds that human activity has had a detectable influence on the latitudinal pattern of precipitation change. Such human-induced changes contributed to the increase in precipitation in the Northern Hemisphere mid-latitudes and the decrease in precipitation in the Northern Hemisphere tropics and subtropics that occurred over the twentieth century.

Long-term model simulations show that a linear relationship between atmospheric warming and cumulative CO₂ emissions holds up to 5 trillion tonnes of carbon (EgC), the estimated total fossil fuel resource in the absence of mitigation efforts.

A single-cell atlas of the human lungs, integrating data from 2.4 million cells from 486 individuals and including samples from healthy and diseased lungs, provides a roadmap for the generation of organ-scale cell atlases.

Between 1955 and 2000 stratospheric ozone decreased and tropospheric ozone increased. Model analysis shows that these ozone changes each drove warming of the Southern Ocean through distinct mechanisms and together account for ~30% of the net subsurface Southern Ocean heat content increases over the same period, with the larger contribution from tropospheric increases.

Recent observed global warming is significantly less than that simulated by climate models. This difference might be explained by some combination of errors in external forcing, model response and internal climate variability.

It has been claimed that the early-2000s global warming slowdown or hiatus, characterized by a reduced rate of global surface warming, has been overstated, lacks sound scientific basis, or is unsupported by observations. The evidence presented here contradicts these claims.

Including passive CO₂ uptake as an anthropogenic removal in greenhouse gas accounting systems could undermine the Paris Agreement; measures to address this include acknowledging the need for Geological Net Zero and disaggregated accounting for carbon sinks.

Limiting warming to 1.5 °C requires staying within an allowable carbon budget. An analysis of warming and carbon budgets from the past decade shows that the median remaining budget is 208 PgC, corresponding to about 20 years of emissions at the 2015 rate.

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

Warming is altering subtropical precipitation; however, it is not clear whether this will continue in an equilibrium climate. Using projections to 2300, Southern Hemisphere drying is shown to be a transient response to the meridional temperature gradient changes.

Different methods for determining global mean temperature change are preferable for different purposes, such as estimating carbon budgets versus consistency with the achievement of the Paris Agreement, argues a Perspective that outlines methodological choices and recommends decision pathways.

Uncertainties in projected 21^st century warming were very large a decade ago, increasing the costs of climate change adaptation, especially those associated with long-lived infrastructure. Here we show that through progress in climate policy and climate science, these uncertainties have decreased dramatically over the past decade.

Estimates of carbon budgets compatible with limiting warming to below specific temperature limits are reviewed, and reasons underlying their differences discussed along with their respective strengths and limitations.

Lawrence Reeves et al. report evidence that adult females of the mosquito species Uranotaenia sapphirina feed primarily on annelid hosts. This is the first known example of a mosquito species that specializes on invertebrate blood and suggests that mosquito host use patterns are more diverse than previously recognized.