The subtle origins of surface-warming hiatuses

During the first decade of the twenty-first century, the Earth’s surface warmed more slowly than climate models simulated1. This surface-warming hiatus is attributed by some studies to model errors in external forcing2, 3, 4, while others point to heat rearrangements in the ocean5, 6, 7, 8, 9, 10 caused by internal variability, the timing of which cannot be predicted by the models1. However, observational analyses disagree about which ocean region is responsible11, 12, 13, 14, 15, 16. Here we show that the hiatus could also have been caused by internal variability in the top-of-atmosphere energy imbalance. Energy budgeting for the ocean surface layer over a 100-member historical ensemble reveals that hiatuses are caused by energy-flux deviations as small as 0.08 W m−2, which can originate at the top of the atmosphere, in the ocean, or both. Budgeting with existing observations cannot constrain the origin of the recent hiatus, because the uncertainty in observations dwarfs the small flux deviations that could cause a hiatus. The sensitivity of these flux deviations to the observational dataset and to energy budget choices helps explain why previous studies conflict, and suggests that the origin of the recent hiatus may never be identified

Reconciling conflicting accounts of local radiative feedbacks in climate models

The literature offers conflicting findings about which regions contribute most to increases in the global radiative feedback after a forcing increase. This paper explains the disagreement by discriminating between two common definitions of the local feedback, which use either local temperature or global temperature as their basis. Although the two definitions of feedback have been previously compared in aquaplanet models with slab oceans, here the definitions are compared for the first time in an atmosphere–ocean general circulation model (MPI-ESM1.2) integrated over four doublings of atmospheric CO2 concentrations. Large differences between the definitions can be seen in all feedbacks, but especially in the temperature and water vapor feedbacks. Differences of up to 10 W m22 K21 over the Southern Ocean can be explained by the pattern of surface warming, which weights the local feedbacks and reduces their contribution to the global mean. This finding is, however, dependent on the resolution of analysis, because the local-temperature definition is mathematically inconsistent across spatial scales. Furthermore, attempts to estimate the effect of “pattern weighting” by separating local feedbacks and warming patterns at the gridcell level fail, because the radiative change in key tropical regions is also determined by tropospheric stability via the global circulation. These findings indicate that studies of regional feedback change are more sensitive to methodological choices than previously thought, and that the tropics most likely dominate regional contributions to global radiative feedback change on decadal to centennial time scales. SIGNIFICANCE STATEMENT: Radiative feedbacks are processes that either intensify or damp global surface warming. We compare two ways to define local radiative feedbacks in a climate model and find that the choice of definition drastically impacts the results. Differences in feedback between the definitions are up to 10 W m22 K21 over the Southern Ocean; by comparison, the estimate of the true global feedback is around 21 W m22 K21. Also, one of the definitions is mathematically inconsistent across different scales of spatial aggregation. Our findings matter because they help to reconcile disagreement in previous studies about which regions dominate global radiative feedback change in model simulations of global warming. Ó 2022 American Meteorological Society

Indigenous knowledge on climate change adaptation: a global evidence map of academic literature

There is emerging evidence of the important role of indigenous knowledge for climate change adaptation. The necessity to consider different knowledge systems in climate change research has been established in the fifth assessment report (AR5) of the Intergovernmental Panel on Climate Change (IPCC). However, gaps in author expertise and inconsistent assessment by the IPCC lead to a regionally heterogeneous and thematically generic coverage of the topic. We conducted a scoping review of peer-reviewed academic literature to support better integration of the existing and emerging research on indigenous knowledge in IPCC assessments. The research question underpinning this scoping review is: How is evidence of indigenous knowledge on climate change adaptation geographically and thematically distributed in the peer-reviewed academic literature? As the first systematic global evidence map of indigenous knowledge in the climate adaptation literature, the study provides an overview of the evidence of indigenous knowledge for adaptation across regions and categorises relevant concepts related to indigenous knowledge and their contexts in the climate change literature across disciplines. The results show knowledge clusters around tropical rural areas, subtropics, drylands, and adaptation through planning and practice and behavioural measures. Knowledge gaps include research in northern and central Africa, northern Asia, South America, Australia, urban areas, and adaptation through capacity building, as well as institutional and psychological adaptation. This review supports the assessment of indigenous knowledge in the IPCC AR6 and also provides a basis for follow-up research, e.g. bibliometric analysis, primary research of underrepresented regions, and review of grey literature

Effects of fructooligosaccharides on cecum polyamine concentration and gut maturation in early-weaned piglets

Polyamines are molecules involved in cell growth and differentiation and are produced by bacterial metabolism. However, their production and effects by the microbiota selected by fructooligosaccharides consumption are controversial. In this study, we investigated the influence of supplementation of fructooligosaccharides on the cecal polyamine production by the microflora selected, and its effect on gut maturation in newborn piglets. Twenty piglets were fed a control formula (n = 10) or a formula supplemented with fructooligosaccharides (8 g/l) (n = 10) for 13 days. Colony-forming unit’s count of cecal content was done in different media. Several intestinal development parameters were measured as well as the polyamine concentration in the cecal mucosa and cecal content. A dose-dependent study on in vitro polyamine production by fructooligosaccharides addition to the isolated cecal content was performed. Bifidogenic activity of fructooligosaccharides increased polyamine concentration in the cecal content, mainly putrescine, with no beneficial effect on gut maturation. Bifidobacterium spp. were able to produce polyamines, but they were not the most significant bacterial producer of polyamines in the cecum of piglets fed fructooligosaccharides. Bifidogenic activity of fructooligosaccharides did not lead to an increase in gut maturation in piglets of 15 days of age although polyamines were increased in the cecal content