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Humid heat extremes, characterized by high wet bulb temperature (Tw), pose significant health risks. While strong El Niño events are known to affect the frequency of extreme Tw days, the distinct impacts of Central Pacific (CP) and Eastern Pacific (EP) El Niño events remain understudied. Using a 12‐member CMIP6 ensemble at discrete global warming targets (+1.5, 2, 3, 4°C), this study shows progressively enhanced humid heat extent during EP events primarily in Mainland Southeast Asia, while South Asia experiences regionally opposing effects from EP and CP events. EP and CP events drive distinctly different, regionally varying patterns of dangerous Tw, yet both significantly increase the affected population and area impacted by humid heat extremes at all global warming levels. This amplification surpasses the impact of an additional degree of global warming, highlighting El Niño's compounding effect on heat stress threats across warmer climates. Plain Language Summary Humid heat extremes, characterized by high wet bulb temperature (Tw), pose health risks even to young, healthy individuals. While strong El Niño events are known to affect extreme Tw days, the impact of different El Niño types (Central Pacific and Eastern Pacific) has not been well studied. Using historical data and future climate projections, we examined how these El Niño types affect the frequency and spatial extent of dangerous Tw. Our analysis shows that under future warming, Eastern Pacific and Central Pacific El Niño events drive distinctly different, regionally varying patterns of dangerous Tw, yet both significantly increase the affected population and area impacted by humid heat extremes at all global warming levels. Even at low global warming levels, during El Niño events, the population exposed to dangerous Tw is expected to be equal to that exposed regularly when the mean warming is more than four times higher. This highlights the need to consider El Niño diversity in assessing the additional heat stress in heavily populated regions as the planet warms and approaches the critical threshold of heat stress. Key Points El Niño events enhance humid heat stress metric exceedances regionally to levels expected under much warmer mean climatological conditions Central Pacific events broadly exacerbate humid heat; Eastern Pacific events have localized amplifications but also mitigating effects Under future warming, Eastern (Central) Pacific events primarily affect Mainland Southeast (East) Asia; South Asia may see varied effects

Limited understanding of the climate system imposes upon policy makers an intimate reliance on results from Earth System Models (ESMs). However, climate simulations are necessarily incomplete since many strong channels through planetary scale biology and geochemistry remain too complex or poorly comprehended to include. This paper presents and describes an interactive, public domain website detailing the role of two marine biogeochemical (mBGC) feedback loops currently excluded from many ESMs (www.marinefeedbacks.com). Every page on the website includes images or videos to foster engagement with its technically challenging content. Simultaneously, fundamentals of the natural science involved are reinforced. The site includes subsections of the following nature; background information, executive summaries for each feedback type, detailed descriptions of the chemical mechanisms, climate change impact, and recommendations for future research. The information provided is firmly grounded in the technical literature but is designed specifically for accessibility to non-scientists. Particular targets for the material are the next-generation of decision makers and those framing the international climate agenda. It is hoped that a site with tailored pedagogical value may contribute to well informed policy formulation and legislation.

Utilizing the reduced-complexity model Hector, a regional scale analysis was conducted quantifying the possible effects climate change may have on dimethyl sulfide (DMS) emissions within the oceans. The investigation began with a review of the sulfur cycle in modern Earth system models. We then expanded the biogeochemical representation within Hector to include a natural ocean component while accounting for acidification and planktonic community shifts. The report presents results from both a latitudinal and a global perspective. This new approach highlights disparate outcomes which have been inadequately characterized via planetary averages in past publications. Our findings suggest that natural sulfur emissions (ESN) may exert a forcing up to 4 times that of the CO2 marine feedback, 0.62 and 0.15 Wm−2, respectively, and reverse the radiative forcing sign in low latitudes. Additionally, sensitivity tests were conducted to demonstrate the need for further examination of the DMS loop. Ultimately, the present work attempts to include dynamic ESN within reduced-complexity simulations of the sulfur cycle, illustrating its impact on the global radiative budget.

We have recently argued that marine interfacial surface tension must have a distinctive biogeography because it is mediated by fresh surfactant macromolecules released locally through the food web. Here we begin the process of quantification for associated climate flux implications. A low dimensionality (planar) equation of state is invoked at the global scale as our main analysis tool. For the reader’s convenience, fundamental surfactant physical chemistry principles are reviewed first, as they pertain to tangential forces that may alter oceanic eddy, ripple, and bubble fields. A model Prandtl (neutral) wind stress regime is defined for demonstration purposes. It is given the usual dependence on roughness, but then in turn on the tension reduction quantity known as surface pressure. This captures the main net influences of biology and detrital organics on global microlayer physics. Based on well-established surrogate species, tangent pressures are related to distributed ecodynamics as reflected by the current marine systems science knowledge base. Reductions to momentum and related heat-vapor exchange plus gas and salt transfer are estimated and placed on a coarse biogeographic grid. High primary production situations appear to strongly control all types of transfer, whether seasonally or regionally. Classic chemical oceanographic data on boundary state composition and behaviors are well reproduced, and there is a high degree of consistency with conventional micrometeorological wisdom. But although our initial best guesses are quite revealing, coordinated laboratory and field experiments will be required to confirm the broad hypotheses even partially. We note that if the concepts have large scale validity, they are super-Gaian. Biological control over key planetary climate-transfer modes may be accomplished through just a single rapidly renewed organic monolayer.

We apply principles of Gibbs phase plane chemistry across the entire ocean-atmosphere interface to investigate aerosol generation and geophysical transfer issues. Marine surface tension differences comprise a tangential pressure field controlling trace gas fluxes, primary organic inputs, and sea spray salt injections, in addition to heat and momentum fluxes. Mapping follows from the organic microlayer composition, now represented in ocean system models. Organic functional variations drive the microforcing, leading to (1) reduced turbulence and (by extension) laminar gas-energy diffusion; plus (2) altered bubble film mass emission into the boundary layer. Interfacial chemical behaviors are, therefore, closely reviewed as the background. We focus on phase transitions among two dimensional “solid, liquid, and gaseous” states serving as elasticity indicators. From the pool of dissolved organic carbon (DOC) only proteins and lipids appear to occupy significant atmospheric interfacial areas. The literature suggests albumin and stearic acid as the best proxies, and we distribute them through ecodynamic simulation. Consensus bulk distributions are obtained to control their adsorptive equilibria. We devise parameterizations for both the planar free energy and equation of state, relating excess coverage to the surface pressure and its modulus. Constant settings for the molecular surrogates are drawn from laboratory study and successfully reproduce surfactant solid-to-gas occurrence in compression experiments. Since DOC functionality measurements are rare, we group them into super-ecological province tables to verify aqueous concentration estimates. Outputs are then fed into a coverage, tension, elasticity code. The resulting two dimensional pressure contours cross a critical range for the regulation of precursor piston velocity, bubble breakage, and primary aerosol sources plus ripple damping. Concepts extend the water-air adsorption theory currently embodied in our OCEANFILMS aerosol emissions package, and the two approaches could be inserted into Earth System Models together. Uncertainties in the logic include kinetic and thermochemical factors operating at multiple scales.